Luminous Landscape Forum
Raw & Post Processing, Printing => Printing: Printers, Papers and Inks => Topic started by: Bart_van_der_Wolf on April 27, 2015, 06:30:57 am
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Hi folks,
Due to the recurring questions about print resolution (limited by printer and or medium), I sat down and created a super (too ?) critical resolution test target which should reveal any shortcomings in the output process. It's merciless, and currently in the testing phase of design, but I wanted to share it already, in case someone can use it in it's current stage for optimizing their output workflow.
There are two versions available for download and personal use, mainly intended for testing inkjet printers:
Test target for 600 PPI printers (https://www.dropbox.com/s/zzh73f3g4rwd4c5/PrintRes_130mm_600PPI.tif?dl=0) (e.g. Canon / HP)
Test target for 720 PPI printers (https://www.dropbox.com/s/0g5j2j7nmjdt0zp/PrintRes_130mm_720PPI.tif?dl=0) (e.g. Epson)
If printed at the indicated PPI resolution, the final target output should have a square size of 130 millimetres (5.11811... inches).
There is a number of patterns on the target that will allow to quite accurately measure the actual resolution that the printer/ink/media combination can produce. That's also useful if one is searching for a medium that has relatively low ink diffusion characteristics. Some media are sharper than others, on the same printer.
There is a central 'star' shaped pattern that should be resolved all the way down to the green concentric circle near its center. There is also a red circle at half the maximum resolution, which should help to estimate intermediate resolution in any orientation (not only horizontal or vertical). Inside the green circle is a pattern of sinusoidal 'rings' which also get higher in resolution as they approach the green circle, and they are very sensitive to ink diffusion which tends to make the rings seemingly darker as the detail gets smaller. Differences in print-head alignment and paper feed accuracy should show by the appearance of aliasing patterns and differing resolution between horizontal and vertical resolution limits.
At the bottom edge of the target is a greyscale. Actually it's a combination of 5 greyscales that each use more steps to produce the full gradient. The top one is 32 steps, followed by 64 steps, 128 steps, 256 steps, and finally virtually continuous tone (16-bit/channel precision). There is no dithering in the gradients, so they should show discontinuities and non-gray profiling issues quite well.
On the left and top edge there are blocks of uniform resolution, each with 4 patches with horizontal, vertical and diagonal sinusoidal patterns of the indicated resolution, marked in cycles/mm (assumes correct print resolution, 600 PPI or 720 PPI, was used). In principle, these should print at equal (medium-grey) density regardless of the pattern orientation. But differences in print-head alignment and paper feed accuracy may cause density differences and/or aliasing patterns, especially on the higher resolution patches. Non-linearities in the match between output profile and media can also cause what appears to be aliasing patterns, but they are actually something else.
The top left-hand side patches are at the printer's maximum resolution, 1 pixel wide lines. That level of resolution is much higher than normally required for good print resolution. Good resolution is achieved at 5 cycles/mm, and excellent print resolution is achieved at 8 cycles/mm, when viewed at reading distance in good (not too dim, not too bright) light levels. The 'excess' resolution can be put to good use when using high quality output sharpening, and for subjects with very fine lines or sharp edges and high contrast.
At the right-hand edge of the target there is continuous sweep of diagonal sinusoidal patterns that should ideally look like a smooth increase of resolution without aliasing patterns or disruptions. They are also resolution marked in cycles/mm, and the range is chosen to be able and encode the sinusoids relatively accurately, and encompass all practically relevant levels of output resolution.
There are also two smaller pattern blocks of 1, 2, and 3 line wide gradients that allow to estimate if and how the highest resolutions will start to lose the ability to mix intermediate tones. They attempt to show the trade-off between resolution and color mixing of intermediate tones by the printer driver's dithering algorithms.
Finally there is a small patch of high and very low contrast lines, 1, 2 , and 3 pixels wide, at the top left corner of the grey square of the star background.
Make sure to first do a head alignment on the actual paper (thickness) that the target will be printed on. It will save you from disappointing results, which may still occur due to the overly critical nature of the target. The patterns on the target itself are virtually artifact free, so any irregularities that show up, must be caused by the output workflow (e.g. profiling), or printer driver settings or mechanical printer tolerances. The target itself is tagged as having an Adobe RGB colorspace, but one can always assign another colorspace to see if the profile conversions to the output medium have any adverse effects on resolution.
That's about it for the moment.
Cheers,
Bart
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Hi Bart,
This comes in handy just at this moment for me, and I have downloaded it - many thanks for making it available.
I have one question for you - I have always been given to understand that the native output resolution the Epson printing process works with is 360ppi for all but the "Finest Detail" setting, which when selected changes the driver's "native resolution" to 720ppi, which setting is only recommended for vector graphics, not photographic prints. Hence the Epson professional printers are actually "360 printers" for most purposes. Is your target equally usable for 360 and 720? (This of course is not to be confused with the Print Quality settings - 720, 1440, 2880 in dpi).
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Hi Bart,
This comes in handy just at this moment for me, and I have downloaded it - many thanks for making it available.
Hi Mark,
You're welcome, and good timing then...
I have one question for you - I have always been given to understand that the native output resolution the Epson printing process works with is 360ppi for all but the "Finest Detail" setting, which when selected changes the driver's "native resolution" to 720ppi, which setting is only recommended for vector graphics, not photographic prints.
There has been some confusion about that, but by selecting 'finest detail' option you do not hurt your images at all, even for normal (non-vector art) images. In fact, as also Jeff Schewe confirms, when your image detail is enough for the output size (i.e. > 360 PPI), it is better to upsample to 720 PPI than to throw away detail that you already have. This of course assumes that the image has not only enough pixels, but also enough intrinsic resolution in it.
Hence the Epson professional printers are actually "360 printers" for most purposes. Is your target equally usable for 360 and 720? (This of course is not to be confused with the Print Quality settings - 720, 1440, 2880 in dpi).
So for the above mentioned reason, I suggest to print it at 720 PPI with 'finest detail' selected. Of course you can also print it at the same output size (130mm) without the 'finest detail' option, and see what (detail) is lost (and automatic driver induced resampling artifacts gained). Alternatively you can print the target at 360 PPI at twice the size (260mm), and you should also be fine, without resampling artifacts, but at a lower resolution (and it obviously takes more ink and paper).
Cheers,
Bart
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Thanks for your quick response Bart. While I appreciate your technical insight into this matter, it has been a subject of considerable uncertainty with changing views over time, hence I shall do some further research on it - both hands-on and consultation. May not be the last word either, but perhaps useful. Your target will be helpful for this and pleased to know I can use it at 360 too. Thanks.
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Hi Mark,
You're welcome, and good timing then...
Cheers,
Bart
Well a week later than the last target collage that I made :-) Including a 600 PPI sinusoidal pattern that might have been your work too but I am not sure. Can be improved so I certainly will try your new target.
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2014 update, 700+ inkjet media white spectral plots
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Add my thanks for this, too, Bart.
I have just downloaded it and expect to learn a good deal about just how my 3800 behaves with the various settings.
Eric M.
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Bart, Thanks! As with the other Mark, this is timely for me as well. I've been printing with a new Epson Surecolor P600, and it's the first printer I've ever owned with a whopping 5760 dpi setting. In fact it only offers a choice of "superfine 1440 dpi", "photo1440 dpi", or "5760 dpi" with various combinations of High speed on and off, and finest details, etc., but no "2880 dpi" setting. This jump to 5760 of course went begging for some quick and dirty test prints to see if I could tell the difference in print quality at normal viewing distances, and my tentative results so far now also beg for further detailed investigation. Your target is going to come in handy. For my first test I sent the printer an image with lots of fine frequency details, and the source file was over 450 dpi, so first I upsampled it to 720, then put the different driver screening options through their paces. Well, it's subtle, really subtle, but it's also pretty obvious that the battleground isn't the resolution. It's how the driver screening pattern is handling the mid frequency modulation. So, the 1440 dpi setting are arguably just as "sharp" maybe even a tad sharper to my eye than the 5760 dpi, but the 5760 dpi does have some inherent "analog" smoothness that can't just be ignored. Anyway, it's a challenging effort to say anything definitive at the moment, but your target is going to help me get there.
FWIW, the well known fact that acutance or perceived sharpness in and image does not always correlate with resolving power plays out magnificently with many digital output devices, inkjet maybe even to an extreme. Here's an article I wrote some time ago about the new (at the time) Fuji Drylab printer which was a four color inkjet technology intended for the 4x6 photo finishing market. http://www.aardenburg-imaging.com/news.47.html
I compared its output to the Fuji Frontier 390 (RA-4 wet process) printer and to a six color home inkjet photo printer. If you scroll down and look through the various pictures in the article of the young lady (my daughter) and her new puppy, there is a very good example of this acutance versus resolution issue. The Fuji Drylab could not reproduce the fine ribbed lining detail in her sweater, yet to anyone looking at the prints, it was decidedly sharper than the Fuji Frontier 390 output that it was replacing. On a more subtle scale, I'm pretty convinced that this is also happening in the P600 driver such that the 1440 dpi output is probably going to be the "preferred" setting for most uses as it is faster yet seems to sacrifice little or no apparent perceptual print sharpness even though I suspect your target is likely to show that the 5760 dpi setting outperforms on resolution.
best,
Mark
http://www.aardenburg-imaging.com
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Well a week later than the last target collage that I made :-)
Ha, these things seem to inspire each other without knowing about the other work in progress. Must be telepathy.
Including a 600 PPI sinusoidal pattern that might have been your work too but I am not sure. Can be improved so I certainly will try your new target.
Well, it might be something I made for testing of camera resolution. But this target is specific for printers and probably goes a lot further, and maybe too far, in challenging the printer. It takes extremely little misalignment or paper feed issue to produce artifacts as a signal that there is an issue (however minor it may be).
It may be too sensitive, since also changes in gamma (strong profile adjustments?) can generate aliasing artifacts. I'd like to hear it if that is the case, so I can perhaps redesign parts of it when I get some time. And I'm not sure if on the Mac it is possible to assign the output profile to the target and then print it as if there is no profile involved, to circumvent profiling effects.
Feedback is appreciated.
Cheers,
Bart
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Bart, Thanks! As with the other Mark, this is timely for me as well. I've been printing with a new Epson Surecolor P600, and it's the first printer I've ever owned with a whopping 5760 dpi setting. In fact it only offers a choice of "superfine 1440 dpi", "photo1440 dpi", or "5760 dpi" with various combinations of High speed on and off, and finest details, etc., but no "2880 dpi" setting.
Hi Mark,
Yes, these high DPI settings are mainly changing the dithering behavior, but not the real resolution. Resolution is still limited to 720 pixels per inch on Epsons, and only if the 'finest detail' option is used (otherwise it drops back to 360 PPI).
FWIW, the well known fact that acutance or perceived sharpness in and image does not always correlate with resolving power plays out magnificently with many digital output devices, inkjet maybe even to an extreme.
Yes, there s more to it than just resolution. And there is also a lot that post-processing can do for an image even before it gets sent to the printer driver.
Here's an article I wrote some time ago about the new (at the time) Fuji Drylab printer which was a four color inkjet technology intended for the 4x6 photo finishing market. http://www.aardenburg-imaging.com/news.47.html
Thanks, I'll have a read later.
Cheers,
Bart
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Hi Bart,
This comes in handy just at this moment for me, and I have downloaded it - many thanks for making it available.
I have one question for you - I have always been given to understand that the native output resolution the Epson printing process works with is 360ppi for all but the "Finest Detail" setting, which when selected changes the driver's "native resolution" to 720ppi, which setting is only recommended for vector graphics, not photographic prints. Hence the Epson professional printers are actually "360 printers" for most purposes. Is your target equally usable for 360 and 720? (This of course is not to be confused with the Print Quality settings - 720, 1440, 2880 in dpi).
Hi Mark:
Here's a column you might enjoy:
http://theonlinephotographer.typepad.com/the_online_photographer/2010/01/how-sharp-is-your-printer-how-sharp-are-your-eyes.html
I have printed large prints from stitched 645D files at 360 and 720 ppi on a 4900; I was unable to see any significant difference even with a 10x loupe.
Tom
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Hi Mark:
Here's a column you might enjoy:
http://theonlinephotographer.typepad.com/the_online_photographer/2010/01/how-sharp-is-your-printer-how-sharp-are-your-eyes.html
I have printed large prints from stitched 645D files at 360 and 720 ppi on a 4900; I was unable to see any significant difference even with a 10x loupe.
Tom
In light of Epson's clearly stated advice on this matter and my own previous trials, this is a consistent observation.
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It may be too sensitive, since also changes in gamma (strong profile adjustments?) can generate aliasing artifacts. I'd like to hear it if that is the case, so I can perhaps redesign parts of it when I get some time. And I'm not sure if on the Mac it is possible to assign the output profile to the target and then print it as if there is no profile involved, to circumvent profiling effects.
Feedback is appreciated.
Cheers,
Bart
I noticed that your new target has AdobeRGB assigned and recently I went for sRGB with B&W work for some practical reasons. Will see how I can reduce any influence but the tone range curves are close. The 16 bit dithering in Qimage Ultimate is another hurdle to take, the one Mike added after your comments on 16 bit profiling etc.
Dotgain indicators that show at which density dotgain happens may help to optimize the output. With multiple ink channels and (custom) partitioned monochrome inks in use, dotgain is no longer just showing up near Dmax. Feedback on that can help in tweaking media presets or simpler in a choice of a better media preset
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2014 update, 700+ inkjet media white spectral plots
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I noticed that your new target has AdobeRGB assigned and recently I went for sRGB with B&W work for some practical reasons. Will see how I can reduce any influence but the tone range curves are close.
That's correct, in an attempt to have a predictable uniform gamma, but you can just assign sRGB instead if that suits your B/W workflow better. Gamut should not be an issue when printing B/W with color ink for toning or neutralization.
The 16 bit dithering in Qimage Ultimate is another hurdle to take, the one Mike added after your comments on 16 bit profiling etc.
That's the reason why I designed the target as a 16-bit/channel image (to allow a test of the dither options). Qimage will dither the 16-bit input to 8-b/ch when reading and converting the file, and then offers an optional dithering after profile conversion and output sharpening. The initial dither, going from 16 to 8-b/ch, is not optional. One can eliminate it though, by first creating an 8-b/ch version of the target and then use that version as input for testing.
Dotgain indicators that show at which density dotgain happens may help to optimize the output. With multiple ink channels and (custom) partitioned monochrome inks in use, dotgain is no longer just showing up near Dmax. Feedback on that can help in tweaking media presets or simpler in a choice of a better media preset
Yes, that's what I had in mind with some of the gradual versus discrete resolution design. In principle, assuming a neutral profile, the density of the different fixed resolution patches should be the same (on average), but due to dot gain or ink diffusion the higher resolution patches will become darker than average (because the paper white will get contaminated). Some papers behave better than others.
I have thought about adding 'white dots on black' patterns, or cross-hatched patches, for dot gain analysis. But for the moment I decided that it might be better to create some neighboring patches with significantly different resolution. That's why I divided the full and half cycle/mm patches in two full cycle difference neighbor sequences, bordering to the medium grey of the star background.
The benefit of discrete resolution patches is also that they tend to make a clearer 'now you see it, now you don't' difference. The gradual sweep allows to pinpoint intermediate values for the most meaningful resolutions, if half cycle/mm differences are too large a jump for some particular application. The central 'rings' in the 'star' are very sensitive to dot gain effects, unless the dot gain compensation in the output profile is perfect.
Cheers,
Bart
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Thanks for the target! I do want to test this on my Epson 3880, I've done a head alignment and will print with Glossy paper.
I want to make sure I understand the parameters of testing. I understand I need to output the document as is, at 720PPI with and without using Finest Detail settings in the driver.
Would it be fair and correct to resample the target itself to 180PPI, 300PPI and make the print so it's the same size as above?
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I have one question for you - I have always been given to understand that the native output resolution the Epson printing process works with is 360ppi for all but the "Finest Detail" setting, which when selected changes the driver's "native resolution" to 720ppi, which setting is only recommended for vector graphics, not photographic prints.
In the two prints I just made, the Finest Detail makes a visual difference and shows no moiré like the print without this setting being on. The 1.42 area shows detail with this setting on, without it's nearly all a solid gray! As Spock would say, fascinating!
IF I had a true 720PPI's of data, it appears it would be a mistake not to have Finest Detail at least with Bart's image. For real images, I'm not sure but I don't know why not.
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Thanks for the target! I do want to test this on my Epson 3880, I've done a head alignment and will print with Glossy paper.
I want to make sure I understand the parameters of testing. I understand I need to output the document as is, at 720PPI with and without using Finest Detail settings in the driver.
Hi Andrew,
Yes, you'd want to enable the 'finest detail' option, if you want to test for the highest attainable resolution on your paper of choice. By not checking the box for 'finest detail' the printer will default to downsampling to 360 PPI when the target is printed as 130mm size.
Would it be fair and correct to resample the target itself to 180PPI, 300PPI and make the print so it's the same size as above?
You can resample the target and see what the effect is, although resampling may/will create its own artifacts (which is why we want to avoid the printer driver doing it). That's what the discussion about printing at 360 or 720 PPI is often about, the lackluster resampling quality of the automatic resampling to either 360 or 720 depending on the driver parameters. It's best to sent high quality 'pre-sampled' data at exactly whatever resolution the printer driver expects. Predictable behavior is the result we are usually after, even if it's not 100% perfect.
If you are thinking of other types of printers, e.g. c-print types or dry process, then it depends on the technology it uses which target to use, the 600 or 720 PPI version. It might be wise to then let the print engine use the built in PPI tag and output at whatever (larger) size that leads to. A Durst Lambda or Epsilon for example might be best tested with the smaller 600 PPI target version, to keep the output size low, but it might want to print at 254 PPI, or 300 or 400, who knows (the printer operator should, but ...).
Cheers,
Bart
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In the two prints I just made, the Finest Detail makes a visual difference and shows no moiré like the print without this setting being on. The 1.42 area shows detail with this setting on, without it's nearly all a solid gray! As Spock would say, fascinating!
IF I had a true 720PPI's of data, it appears it would be a mistake not to have Finest Detail at least with Bart's image. For real images, I'm not sure but I don't know why not.
Thanks for the feedback, it seems to do what it is supposed to (show real resolution limits, however small they may be). This allows to compare media choices, when detail must not be compromised by ink diffusion. It also demonstrates the effect of the 'finest detail' option.
Whether it's significant/useful enough to use 720 PPI, assuming enough detail is in the source image to exceed 360 PPI at the intended output size, is still an open choice. But do remember that with specific output sharpening (after resampling to 720 PPI), one can do more sharpening because there are more pixels to sharpen. At 360 PPI we need to be much more careful and avoid sharpening artifacts, because visual acuity on average is good enough to spot the trouble at reading distance.
Cheers,
Bart
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Bart: thanks so much! This is a thing of beauty and I can't begin to imagine how you created it. Presumably not line by line in Photoshop. <g> Fun just to zoom it in and out using scroll wheel, watching the moire patterns morph on the monitor.
Bit of feedback from a less-technical user. I have a 3880 and have printed it so far on a PLPP clone, a PGPP clone, and Hahn. Photo Rag Baryta.
Both on my monitor and my 720 prints the left and top patches look just fine with a loupe, but each vertical box is lighter and each horizontal is darker than the diagonals in the same set, which are equal. This seems to be more along the lines of moire, given the way this disappears under a loupe or in the case of the monitor, when zoomed in to 100%.
My 3880 is maybe 2 years old and had never had a head alignment run, so I printed it before and after an auto alignment at 720 PPI. Both look identical, right down to the naked-eye-visible and loupe-visible moire patterns. Since I'm seeing clear line separation without moire right into the 9s, I'm taking that to indicate my alignment was and remains good. As well as a paper fineness test, this may serve people just as much as a head alignment check.
Another interesting thing for me was to print the target at 720 and 360 (no other change than Finest Detail checked or unchecked). The individual lines look equally fine. They just bleed together a bit sooner without Finest Detail being enabled.
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Bart: thanks so much! This is a thing of beauty and I can't begin to imagine how you created it. Presumably not line by line in Photoshop. <g> Fun just to zoom it in and out using scroll wheel, watching the moire patterns morph on the monitor.
Hi Dale,
Indeed, I used some software assistance to do most of the calculations into pixel values for me. The coarse display sampling will indeed show all sorts of aliasing when zooming in/out.
Bit of feedback from a less-technical user. I have a 3880 and have printed it so far on a PLPP clone, a PGPP clone, and Hahn. Photo Rag Baryta.
Both on my monitor and my 720 prints the left and top patches look just fine with a loupe, but each vertical box is lighter and each horizontal is darker than the diagonals in the same set, which are equal. This seems to be more along the lines of moire, given the way this disappears under a loupe or in the case of the monitor, when zoomed in to 100%.
My 3880 is maybe 2 years old and had never had a head alignment run, so I printed it before and after an auto alignment at 720 PPI. Both look identical, right down to the naked-eye-visible and loupe-visible moire patterns. Since I'm seeing clear line separation without moire right into the 9s, I'm taking that to indicate my alignment was and remains good. As well as a paper fineness test, this may serve people just as much as a head alignment check.
Yes, alignment seems to be consistent, and it's a good way to check if things deteriorate over time or not. When mixing different paper thicknesses it may help to do a more frequent realignment.
It is most likely that the (horizontal) head and (vertical) paper-feed pitch is slightly different (paper transport slipping slightly between rollers?). This could be verifiable by measuring the squareness (130 x 130 mm) of the printed target. The target is very sensitive to tiny differences, so it might also be a bit of moiré but that would more likely produce more noticeable waves of brighter and darker cycles, out of sync with the sinusoidal pattern. So my guess is non-squareness, although it might be too small to cause real issues in practice.
Another interesting thing for me was to print the target at 720 and 360 (no other change than Finest Detail checked or unchecked). The individual lines look equally fine. They just bleed together a bit sooner without Finest Detail being enabled.
Yes, for some subjects it can make a difference, for others it is not important. Especially very fine line and edge detail, together with output sharpening after resampling, will benefit most.
Thanks for the feedback.
Cheers,
Bart
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Hi Bart, thank you for the targets. These are brilliant. Previously I used your camera resolution target to check alignment and positioning accuracy for my printer.
The single pixel lines are super taxing on the printer. My Canon iPF8400 can resolve both the horizontal and vertical lines perfectly when it first arrived, but it underwent a carriage assembly replacement and now the vertical lines (perpendicular to the direction of head travel) are not as crisp or well defined as the horizontal lines. The patch looks a little more dense, if memory serves.
I am working on other things at the moment but I would love to try out the new target soon. Getting the printheads to be perfectly aligned is surprisingly difficult. I have tried to run several manual and auto (including the intitial setup adjustment, which is the most thorough) and realised that the initial head adjustment is the best and most likely to be successful for my iPF8400. The manual adjustment was too unpredictable and dodgy, and does not print adjustment patterns for yellow and one other color I think, because I suspect it would be too faint to see. There usually still is some minor positioning errors over the page, especially in the initial few inches of the paper because of the curl from the roll.
I have seen a definite resolution difference between 300ppi and 600ppi data sent to this printer. Ming Thein has also shown a big improvement going from 360 ppi to 720 ppi on the Epson 9900 on his blog (http://blog.mingthein.com/2014/10/30/ultraprints-vs-normal-prints-visualising-the-difference/).
This is great, can't wait to try it! Thank you. :)
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Hi Bart, thank you for the targets. These are brilliant. Previously I used your camera resolution target to check alignment and positioning accuracy for my printer.
Hi Samuel, you're welcome. Yes, the camera resolution target is also somewhat usable for testing the printer quality, because it has some checks built in to test for good output quality before shooting it with a camera. It wouldn't make sense to test a camera if the test target is no good.
The single pixel lines are super taxing on the printer. My Canon iPF8400 can resolve both the horizontal and vertical lines perfectly when it first arrived, but it underwent a carriage assembly replacement and now the vertical lines (perpendicular to the direction of head travel) are not as crisp or well defined as the horizontal lines. The patch looks a little more dense, if memory serves.
The print has a known (presumably non-resampled) output size, unlike shooting a target with a camera that will vary the on sensor image magnification with focal length and shooting distance, and add blur due to defocus and diffraction. That's why I could up the ante for the print resolution target detail, and add fixed/discrete resolutions with known physical characteristics. That also made it much easier to visually compare how much ink diffusion blurs detail and adds density due to dot gain. The influence of ink/media combinations on resolution becomes better visible, and even quantifiable.
Another use for the target is then to actually demonstrate how viewing distance will affect the resolution requirements. With a good print of the target (even at a magnified output size), one can view it at different distances, and conclude that at a larger distance one can print larger without visual penalty (assuming proper resampling and output sharpening). Being able to visually resolve the 8 cycles/mm patch detail, indicates excellent output resolution, but much harder to even see than the already good 5 cycles/mm detail.
I am working on other things at the moment but I would love to try out the new target soon. Getting the printheads to be perfectly aligned is surprisingly difficult. I have tried to run several manual and auto (including the intitial setup adjustment, which is the most thorough) and realised that the initial head adjustment is the best and most likely to be successful for my iPF8400. The manual adjustment was too unpredictable and dodgy, and does not print adjustment patterns for yellow and one other color I think, because I suspect it would be too faint to see. There usually still is some minor positioning errors over the page, especially in the initial few inches of the paper because of the curl from the roll.
Indeed, perfect alignment is a tough goal to achieve. This target is very sensitive, so I wouldn't be surprised if some minor issues remain detectable. But I prefer to aim for a very high goal and almost reach it, than to meet lower standards with relative ease. As long as perfection doesn't become an obsession, it's worthwhile to keep aiming for it.
I have seen a definite resolution difference between 300ppi and 600ppi data sent to this printer. Ming Thein has also shown a big improvement going from 360 ppi to 720 ppi on the Epson 9900 on his blog (http://blog.mingthein.com/2014/10/30/ultraprints-vs-normal-prints-visualising-the-difference/).
This is great, can't wait to try it! Thank you. :)
Yes, hopefully by now, most people are convinced that there is a real benefit beyond 300 or 360 PPI, although it is not equally beneficial for all image content. Also, output sharpening remains an often undervalued asset, and having more pixels allows to do more. There might also be some wide format output limitations as to how many pixels per paper width can be fed to some printer drivers.
Cheers,
Bart
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Thank you Bart for developing and sharing the targets. I think many of us have long wondered "How good is my print (compared to how good it could be)?" Your target is a very useful reference.
When I first printed the 600 ppi target on my HP Z3200 I was more than disappointed....lots of aliasing and banding (that really prevented any reasonable interpretation of printer resolution performance). After two head alignments and paper advance calibrations, and tinkering with the "best/max detail/more passes" settings the printed target hadn't improved.
And then I went back to the target image size as reported by CS6 that was "5.118 inches" at "599.999 pixels/inch" and reset the resolution to "600.000 pixels/inch" (when I'm using a "reference" the first thing I try not to do is to start adjusting the reference). Now the target printed very nicely (without the strange aliasing and banding). The 7 cycle/mm patch prints nearly perfectly.
Thanks again for your longstanding and many contributions to LULA.
Mike Coffey
Prescott, AZ
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Thank you Bart for developing and sharing the targets. I think many of us have long wondered "How good is my print (compared to how good it could be)?" Your target is a very useful reference.
Hi Mike,
You're right, it's perhaps more useful to get a confirmation of what the situation actually is, instead of how it might be in theory.
When I first printed the 600 ppi target on my HP Z3200 I was more than disappointed....lots of aliasing and banding (that really prevented any reasonable interpretation of printer resolution performance). After two head alignments and paper advance calibrations, and tinkering with the "best/max detail/more passes" settings the printed target hadn't improved.
You had me also worried as I was reading this up to here ...
And then I went back to the target image size as reported by CS6 that was "5.118 inches" at "599.999 pixels/inch" and reset the resolution to "600.000 pixels/inch" (when I'm using a "reference" the first thing I try not to do is to start adjusting the reference). Now the target printed very nicely (without the strange aliasing and banding). The 7 cycle/mm patch prints nearly perfectly.
Phew, I'm relieved. I told it was sensitive to small alignment errors, but this is a good warning to double-check the print settings before questioning other things in the setup. And let's face it, 599.999 PPI is not the same as 600 PPI. ;)
Anything better than 5 cycles/mm is exceeding 254 PPI and is considered good quality, so 7 cycles/mm which equals 355.6 PPI, exceeds the 300 PPI limit which proves that more resolution is to be had with the right driver settings. Even better quality, although sometimes very hard to see, is 8 cycles/mm or 406.4 PPI. It may not be achievable with all papers, and maybe not on all printers. It would take very close scrutiny anyway to see it.
Thanks again for your longstanding and many contributions to LULA.
It's my pleasure. I also pick up some useful info here and there, so we all get to benefit by sharing. I wouldn't have known there was a use for such a tool if it weren't for the discussions about print resolution. It wasn't until I came across some print samples that exhibited significant ink diffusion that I wondered what the actual resolution limit was for such materials, and if 600 or 720 PPi was even needed for those. Now we can tell, and also if head alignment or paper travel is holding us back, in which case perhaps some additional cleaning of the transport path or mechanism might help.
Cheers,
Bart
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Bart, I spent this afternoon using your target to evaluation the alignment accuracy of my Canon iPF8400 printer, after a recent 'operation' to a mechanical component. I noticed something immediately - aliasing artifacts in the print. Like Mike, I discovered that the 600ppi target was set to 599.999ppi instead of 600ppi. I resized without resampling to 600ppi and printed again, this time the 'aliasing artifacts' were still present but looked different. Upon closer inspection of the target (digital file) itself on my monitor, I noticed that the cycles/mm lines are not all of equal contrast gradients - the bands I see in the prints correspond to the bands in the target. So my printer was accurately resolving the artifacts in the target afterall. Could you confirm if my observations on this is correct? In your OP you said the target should be virtually free of defects.
I used the Canon 16 bit PS Plug-in to make my prints, on Harman by Hahnemuhle Gloss Baryta. Depending on the media setting used, the Plug-in does not allow for 300ppi input resolution, only 600ppi resolution. Most of the media settings intended for printing on high quality papers have the 300ppi option grayed out. I decided to make two reference prints, one for the 'Highest (max no of passes)' setting and one for 'Highest". The former used to be 32 passes on the X1XX printers, and now is 16 passes on the X3XX and X4XX printers. The latter I believe is 7 passes, used to be 8. I have done this experiment several times before, and have long known about the much smoother dither and more uniform coverage achieved using the 'Highest (max no of passes)' setting. There is a small but slight resolution increase as well. The vertical resolution is somewhat lower, probably to the limitations of the printer, unable to as accurately fire a vertical column of dots as the paper advances over more passes. Horizontal lines are cleaner however, with less overspray effect.
Here is a link to a zip folder containing 4 jpegs of actual size macro photographs of the prints themselves. The magnification is close to 1:1, taken using a Canon 100mm macro lens on a 5D II.
https://www.dropbox.com/s/i0iqzx1qaqj8bdj/Printer%20Resolution%20Target%20comparison.zip?dl=0
Another use for the target is then to actually demonstrate how viewing distance will affect the resolution requirements. With a good print of the target (even at a magnified output size), one can view it at different distances, and conclude that at a larger distance one can print larger without visual penalty (assuming proper resampling and output sharpening). Being able to visually resolve the 8 cycles/mm patch detail, indicates excellent output resolution, but much harder to even see than the already good 5 cycles/mm detail.
Yes, it is very useful for that! What a brilliant way to quantify resolution at viewing distances. To my eyes, the smoother dither of the 'Highest (max no of passes)' setting is visible to about 15 inches away. The higher resolution (cleaner, crisper lines) in the 4 cycles/mm lines are visible to about 3 feet away.
There is a huge speed penalty however, prints take roughly twice as long to print using this setting. For example, a 24 x 36 inch print takes about 30 mins to complete, a long time but I dearly love the quality improvement, which is visible even on textured matte fine art papers.
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Bart, I spent this afternoon using your target to evaluation the alignment accuracy of my Canon iPF8400 printer, after a recent 'operation' to a mechanical component. I noticed something immediately - aliasing artifacts in the print. Like Mike, I discovered that the 600ppi target was set to 599.999ppi instead of 600ppi. I resized without resampling to 600ppi and printed again, this time the 'aliasing artifacts' were still present but looked different. Upon closer inspection of the target (digital file) itself on my monitor, I noticed that the cycles/mm lines are not all of equal contrast gradients - the bands I see in the prints correspond to the bands in the target. So my printer was accurately resolving the artifacts in the target afterall. Could you confirm if my observations on this is correct? In your OP you said the target should be virtually free of defects.
Hi Samuel, great question, which may have been puzzling others as well, but they may have been afraid to ask... Glad you did.
One part of the difficulty is related to the high level of detail that approaches the Nyquist frequency of the printer. To reproduce a high spatial frequency unambiguously, we need more than 2 pixels per cycle. The 2 px/cy is reached by some of the patterns (top left, and near the green circle) but it is still very sensitive to small irregularities.
The difficulty of totally avoiding aliasing most likely has to do with gamma. When you look at the target on your (LCD, because CRT will create other issues) display at 100% zoom, AND that display is perfectly calibrated for Gamma 2.2, it will be possible to see aliasing IF one moves the observing position a bit up or down, or when viewing the display at a non-perpendicular angle. The patterns are calculated to be as perfect as possible in discrete pixels, but also needs a bit of averaging of intermediate tones that actually have multiple levels of brightness across a single discrete pixel. That averaging is calculated to be most neutral at a display Gamma of 2.2.
But even at that level of physical constraint, even the viewing position/angle apparently is able to introduce aliasing. That's how sensitive the patterns are. So it is not surprising that printing, with additional profile conversions and ink diffusion and media surface structure and dithering, will also be hard/impossible to reproduce flawlessly. The goal should therefore be to minimize the flaws, like density difference between horizontal and vertical running cycles. Luckily for us, normal images do not pose such challenges, or at least we cannot see them as clearly (the issues are still there, hidden by variable image detail).
Maybe, the best possible angle of attack would be to assign the output profile to the target and then print it with that same profile (if the OS doesn't interfere), to reduce the risk of gamma conversions between profiles / colorspaces. But I would still expect a certain level of aliasing to occur. Do also note that e.g. Adobe's ACM adds a linear slope to an AdobeRGB tagged colorspace in images in the lowest levels, so even that is not a uniform gamma space under that regime.
You can also, by simulation, learn to detect the difference between gamma induced aliasing, and that caused by dimensional influences (although the dithering patterns may also have an influence). When you (e.g. in Photoshop) temporarily change the overall gamma (in Levels, or with a curves adjustment) of the target (don't save!), you can see that mostly the horizontal/vertical running cycles will show aliasing. The diagonal running cycles can use a 41% higher accuracy of detail placement and are less affected due to being already somewhat gamma averaged or contrast reduced. However, when changing the image size a bit by resampling, the diagonal running cycles will attract a square aliasing pattern, consistent with a higher diagonal resolution capability. In a dithered print these effects may look a bit different, but it's possible that similar effects can be detected.
I used the Canon 16 bit PS Plug-in to make my prints, on Harman by Hahnemuhle Gloss Baryta. Depending on the media setting used, the Plug-in does not allow for 300ppi input resolution, only 600ppi resolution. Most of the media settings intended for printing on high quality papers have the 300ppi option grayed out. I decided to make two reference prints, one for the 'Highest (max no of passes)' setting and one for 'Highest". The former used to be 32 passes on the X1XX printers, and now is 16 passes on the X3XX and X4XX printers. The latter I believe is 7 passes, used to be 8. I have done this experiment several times before, and have long known about the much smoother dither and more uniform coverage achieved using the 'Highest (max no of passes)' setting. There is a small but slight resolution increase as well. The vertical resolution is somewhat lower, probably to the limitations of the printer, unable to as accurately fire a vertical column of dots as the paper advances over more passes. Horizontal lines are cleaner however, with less overspray effect.
Yes, there is also a potential effect due to the droplets being fired at the medium while having a horizontal speed, thus creating a bit of a splatter pattern instead of a purely round drop, depending on the efficiency of the absorption of the top coated layer. So a slower travel speed may give slightly rounder droplet patterns, and unidirectional can look a bit different from bi-directional (in addition to hysteresis in positioning accuracy).
Here is a link to a zip folder containing 4 jpegs of actual size macro photographs of the prints themselves. The magnification is close to 1:1, taken using a Canon 100mm macro lens on a 5D II.
https://www.dropbox.com/s/i0iqzx1qaqj8bdj/Printer%20Resolution%20Target%20comparison.zip?dl=0
Thanks for those. I was planning to post some results, but I'm waiting for the profiler patterns to dry before creating another profile for a printer I'm testing. So you beat me to it ...
The 'Highest (max no of passes)' does show a subtle (but clearly visible) improvement on the limiting resolution, and a much smoother rendering of the star region. Of course we're pixel peeping, and comparing side-by-side, but there is an obvious benefit for improved quality.
The 8 cycles/mm patch looks pretty good, with almost the same density for hor/ver running cycles. The aliasing pattern, suggests a bit more gamma influence than dimensional cause to the aliasing pattern. That seems to be relatively common.
The smoothness is markedly improved, text is cleaner, and the gradient looks better (very well profiled, all the way to black).
The top left patterns demonstrate very good uniform alignment of both print-head as wel as paper travel direction. Again the 'Highest (max no of passes)' setting proves to be superior in resolving fine detail with better smoothness.
Yes, it is very useful for that! What a brilliant way to quantify resolution at viewing distances. To my eyes, the smoother dither of the 'Highest (max no of passes)' setting is visible to about 15 inches away. The higher resolution (cleaner, crisper lines) in the 4 cycles/mm lines are visible to about 3 feet away.
The resolution requirements change linearly with distance (assuming well functioning eyes/correction). So it will be simple to test for different distances. Of course some (often younger) people have better visual acuity than others.
There is a huge speed penalty however, prints take roughly twice as long to print using this setting. For example, a 24 x 36 inch print takes about 30 mins to complete, a long time but I dearly love the quality improvement, which is visible even on textured matte fine art papers.
Yes, speed takes a hit, but another of those urban myths that needs to be dispelled, is that all matte media or even canvas surfaces are blurry. There are huge differences ...
Cheers,
Bart
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One more thing to clarify.
Upon closer inspection of the target (digital file) itself on my monitor, I noticed that the cycles/mm lines are not all of equal contrast gradients - the bands I see in the prints correspond to the bands in the target. So my printer was accurately resolving the artifacts in the target afterall.
I've designed the target as a relatively 'cruel but honest' one, but it is possible to design a 'gentler for softies' version. ;)
To illustrate, I've attached 3 versions of the 8 cycle/mm (horizontal cycles patch area) for 600 PPI printers (next post will have the three for 720 PPI). They have exactly the same spatial frequency, but they differ in the amplitude due to added anti-aliasing. The anti-aliasing may make the target patch look more benign, but it also makes it harder to detect the higher resolution patches resolutions. That will also affect the ability to test potential future print technologies with higher resolutions, and be less sensitive to show resampling artifacts. So the question becomes, which is more useful, gentle or strong (I can create any intermediate level)?
My current take is that, as long as we know what can happen with regard to aliasing, it is beneficial for the test to be relatively sensitive in order to more clearly show small improvements/degradations.
Cheers,
Bart
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Here I've attached 3 versions of the 8 cycle/mm (horizontal cycles patch area) for 720 PPI printers.
Cheers,
Bart
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One part of the difficulty is related to the high level of detail that approaches the Nyquist frequency of the printer. To reproduce a high spatial frequency unambiguously, we need more than 2 pixels per cycle. The 2 px/cy is reached by some of the patterns (top left, and near the green circle) but it is still very sensitive to small irregularities.
The difficulty of totally avoiding aliasing most likely has to do with gamma. When you look at the target on your (LCD, because CRT will create other issues) display at 100% zoom, AND that display is perfectly calibrated for Gamma 2.2, it will be possible to see aliasing IF one moves the observing position a bit up or down, or when viewing the display at a non-perpendicular angle. The patterns are calculated to be as perfect as possible in discrete pixels, but also needs a bit of averaging of intermediate tones that actually have multiple levels of brightness across a single discrete pixel. That averaging is calculated to be most neutral at a display Gamma of 2.2.
But even at that level of physical constraint, even the viewing position/angle apparently is able to introduce aliasing. That's how sensitive the patterns are. So it is not surprising that printing, with additional profile conversions and ink diffusion and media surface structure and dithering, will also be hard/impossible to reproduce flawlessly. The goal should therefore be to minimize the flaws, like density difference between horizontal and vertical running cycles. Luckily for us, normal images do not pose such challenges, or at least we cannot see them as clearly (the issues are still there, hidden by variable image detail).
Hi Bart, thank you for your detailed reply. I think I know what you mean. Here are two crops with an overlay of little red arrows pointing to some of the effects that I saw in the target which appeared like aliasing, which as you describe, is due to the inherent difficulty of using very few discrete pixels to contain a sinusodial pattern.:
(https://dl.dropboxusercontent.com/u/15547362/PrintRes_130mm_600PPI_crop1.png)
(https://dl.dropboxusercontent.com/u/15547362/PrintRes_130mm_600PPI-crop2.png)
While I agree that the gamma is an issue to beware of, zooming to 400% or more and looking at the pixels themselves show the diagonal lines in the 8 cycles/mm box to be darker on average than the horizontal or vertical pixels. When I first saw the print, I mistakenly thought the 4 quadrants were supposed to print with the same average brightness, until I studied the target file.
Regarding the design of the target, I realise that I am really only looking closely at just two parts of the target when using it to evaluate the positioning accuracy of my printer - the single pixel lines in the top left, and the smooth gray background to check the smoothness/evenness of the dither. I'm now wondering how useful the cycles/mm strips are since they look so funny with the aliasing artifacts. What if the patterns are composed of uniform contrast lines instead of sinusoidal lines? Of course they would not be in the same cycles/mm as the current target.
Maybe, the best possible angle of attack would be to assign the output profile to the target and then print it with that same profile (if the OS doesn't interfere), to reduce the risk of gamma conversions between profiles / colorspaces. But I would still expect a certain level of aliasing to occur. Do also note that e.g. Adobe's ACM adds a linear slope to an AdobeRGB tagged colorspace in images in the lowest levels, so even that is not a uniform gamma space under that regime.
I did assign the output profile instead of converting to it, but also tried conversion as well, and could see no real significant difference in the aliasing pattern, except that the target looked much more neutral when converting to printer profile.
Yes, I am aware that Adobe adds a linear slope to all gamma encoded working spaces, not just Adobe RGB. It helps against numbers getting too large as the slope of the curve approaches vertical.
You can also, by simulation, learn to detect the difference between gamma induced aliasing, and that caused by dimensional influences (although the dithering patterns may also have an influence). When you (e.g. in Photoshop) temporarily change the overall gamma (in Levels, or with a curves adjustment) of the target (don't save!), you can see that mostly the horizontal/vertical running cycles will show aliasing. The diagonal running cycles can use a 41% higher accuracy of detail placement and are less affected due to being already somewhat gamma averaged or contrast reduced. However, when changing the image size a bit by resampling, the diagonal running cycles will attract a square aliasing pattern, consistent with a higher diagonal resolution capability. In a dithered print these effects may look a bit different, but it's possible that similar effects can be detected.
I just realised that ! cannot resize you 600ppi target to 599.999ppi in Photoshop! There is no change to the pixel resolution at all. So I have no idea what Mike was seeing. The aliasing pattern in my first bad print was my printer being totally out of alignment initially - there was a mechanical adjustment to the paper feed system and I had not run an alignment yet.
Cool tip about playing with the gamma slider using a levels adjustment! I like that, seeing the aliasing patterns get more or less visible is fun. My display gamma is definitely not a perfect 2.2 (whose is?) and there are slight gamma induced (or tone curve induced) changes, making the aliasing a little more visible than on screen.
Thanks for those. I was planning to post some results, but I'm waiting for the profiler patterns to dry before creating another profile for a printer I'm testing. So you beat me to it ...
Sorry to have stolen your thunder! :) Please post your samples too, I would like to know what you managed to achieve on your end.
And thanks for your observations! I now think the printer is capable of even better performance, after looking at some of my older prints. The new Canon iPFs have excellent built-in linearisation adjustments when performing the paper calibration, which can be paper specific if you have special custom media setting files (built using the iPF6450 with spectrophotometer). The LUTs for the X4XX printers according to Scott Martin have been updated to improve on linearity and smoothness slightly. The printer profile can only do so much if the printer could not separate well near black. In general I am quite happy with its performance, but like everything else, there is room for improvement. Btw I find the smoother vs rougher dither for the two highest quality modes to be more easily seen with the naked eye than in my macro photographs.
Yes, speed takes a hit, but another of those urban myths that needs to be dispelled, is that all matte media or even canvas surfaces are blurry. There are huge differences ...
That was exactly what's on my mind. I can see the smoothness advantage even on canvas, even though the resolution the media is capable of is slightly lower. I print all of my clients work at the highest quality setting, regardless of size, despite the huge efficiency penalty, because it just looks much better up close.
Yes, there is also a potential effect due to the droplets being fired at the medium while having a horizontal speed, thus creating a bit of a splatter pattern instead of a purely round drop, depending on the efficiency of the absorption of the top coated layer. So a slower travel speed may give slightly rounder droplet patterns, and unidirectional can look a bit different from bi-directional (in addition to hysteresis in positioning accuracy).
I would agree with that line of reasoning, but looking closely at the dots under 40x magnification, there is no splatter pattern around the dot? The dots are just not being fired as precisely as they should be, creating a blurry fuzz around what should be a clean edge. I have never been able to see the splatter from my printer's dots! Much too small. In my old tests I clearly observed issues with bidirectional printing affecting dot placement precision, affecting vertical line resolution and hurting the overall smoothness of the dither pattern.
Here is something curious. This is an image of the heading text from a banding adjustment pattern, which seems to be a 4 pass print mode or something like that, certainly not as many passes as Highest (max no. of passes). It may have been 7 passes. The text is much cleaner looking at the edges, proof that my iPF8400 is capable of very clean looking lines. For some reason when there is a lot to do in a pass, printing highly varying detail, over an increased number of passes using the highest quality mode, the dot precision gets all messed up when it comes to clean edges like text.
I am looking again at some of my older prints of your camera resolution chart in the single/double pixel vertical and horizontal lines and noticing cleaner lines, but less accurate dot placement. Like I said in an earlier post, printhead and paper feed alignment is hard to get perfect! I have prints from an Epson 7900 that shows exceedingly smooth dither, but is unable to resolve single pixel lines (@720ppi) as well as the Canons can resolve them (@600ppi). Looks like I need to try aligning the heads yet again...
(https://dl.dropboxusercontent.com/u/15547362/print-mode-dot-precision-compared.jpg)
(right click and open in new tab to view at full size)
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One more thing to clarify.
I've designed the target as a relatively 'cruel but honest' one, but it is possible to design a 'gentler for softies' version. ;)
To illustrate, I've attached 3 versions of the 8 cycle/mm (horizontal cycles patch area) for 600 PPI printers (next post will have the three for 720 PPI). They have exactly the same spatial frequency, but they differ in the amplitude due to added anti-aliasing. The anti-aliasing may make the target patch look more benign, but it also makes it harder to detect the higher resolution patches resolutions. That will also affect the ability to test potential future print technologies with higher resolutions, and be less sensitive to show resampling artifacts. So the question becomes, which is more useful, gentle or strong (I can create any intermediate level)?
My current take is that, as long as we know what can happen with regard to aliasing, it is beneficial for the test to be relatively sensitive in order to more clearly show small improvements/degradations.
Cheers,
Bart
Thanks for these additional patches. Yeah, the lower contrast bottom most patch is probably not as useful, and the artifacts are still quite visible and an educated guess is it will still show in the print. I guess I need to re-think how I use this target for evaluating the resolution of printer+media.
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Anyone try this using Qimage Ultimate and Photoshop CS6?
I got "wildly" different results even though the images both measure out to 5.118" sq. and 720ppi.
Here is a scan of them both, but they are strange to say the least! Same 3880 printer used. Head alignment done yesterday too.
Don't know why PS see the upper right square 14.2 as a B&W only. QI does better there.
I also did one on a 3880 with K7 Piezo inks and QTR. Had to convert it to B&W Gamma 2.2 TIFF and it was better, although some shadows in the vertical line areas of the outside blocks.
Well crap! Even Lightroom 5.7.1 prints differently than PS CS6 too. No B&W square like the image shown below at 14.2 in PS CS6 (Which is the only one of 4 programs to do that!).
This is a cruel joke! Even Corel PaintShop Pro X7 behaves differently, closer to Photoshop CS6 and with a different B&W square in the upper left near 14.2.
Added in Zoner Photo Studio 16 Pro x64 and it too is different in that the B&W squares are now all black! ???
Pick your software. They are all different. Sort of like no two raw converters are the same.
SG
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Like I said in an earlier post, printhead and paper feed alignment is hard to get perfect! I have prints from an Epson 7900 that shows exceedingly smooth dither, but is unable to resolve single pixel lines (@720ppi) as well as the Canons can resolve them (@600ppi). Looks like I need to try aligning the heads yet again...
Canon iPF is better at resolving fine details, so I'm afraid aligning won't help in this regard.
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Hi Bart, thank you for your detailed reply. I think I know what you mean. Here are two crops with an overlay of little red arrows pointing to some of the effects that I saw in the target which appeared like aliasing, which as you describe, is due to the inherent difficulty of using very few discrete pixels to contain a sinusodial pattern.
Correct, it only appears like that because we humans see patterns (like faces in moon surface rocks) even when they are not there. The patterns you correctly point at are merely limitations of pixel size, which aren't small enough to depict gradients accurately. Having said that, I am working on generating even higher quality patterns, but they take a lot longer to calculate (processing time x 100) and then need to be composited into the various composite patterns. May take a while to complete.
While I agree that the gamma is an issue to beware of, zooming to 400% or more and looking at the pixels themselves show the diagonal lines in the 8 cycles/mm box to be darker on average than the horizontal or vertical pixels. When I first saw the print, I mistakenly thought the 4 quadrants were supposed to print with the same average brightness, until I studied the target file.
Not mistakenly, they are supposed to be of equal density (especially the bottom two that run hor/ver), but gamma and profiling may play a trick on us, as well as the difficulty to exactly get intermediate tones from a limited number of inks through dithering. I do see the issue with aliasing patterns, the low frequency waves, and am looking for a way to solve that without compromising the detection sensitivity of errors. Maybe I need to change the overall gamma of the target, or use a different pattern than pure sinusoids (but that would probably need different settings for each dithering method). At the moment I'm calculating the patterns with much higher accuracy to see if that makes a difference. If not, more drastic changes may be needed.
Regarding the design of the target, I realise that I am really only looking closely at just two parts of the target when using it to evaluate the positioning accuracy of my printer - the single pixel lines in the top left, and the smooth gray background to check the smoothness/evenness of the dither. I'm now wondering how useful the cycles/mm strips are since they look so funny with the aliasing artifacts. What if the patterns are composed of uniform contrast lines instead of sinusoidal lines? Of course they would not be in the same cycles/mm as the current target.
Unfortunately, uniform contrast lines only allow fixed pixel resolution measurements, like 600 PPI = 11.81 cy/mm, 300 PPI = 5.91 cy/mm, 200 PPI = 3.94 cy/mm, 150 PPI = 2.95 cy/mm , 120 PPI = 2.36 cy/mm, 100 PPI = 1.97 cy/mm, and only in horizontal/vertical orientation. But those resolutions should be easy for any printer. It's mainly in the region between 300 or 360 PPi and 600 or 720 PPI that we will see the differences in e.g. media/ink diffusion, and there would be no info there without sinusoidal or other intermediate tones.
I did assign the output profile instead of converting to it, but also tried conversion as well, and could see no real significant difference in the aliasing pattern, except that the target looked much more neutral when converting to printer profile.
Good. Frankly, your profiling seems to be quite good.
I just realised that ! cannot resize you 600ppi target to 599.999ppi in Photoshop! There is no change to the pixel resolution at all. So I have no idea what Mike was seeing. The aliasing pattern in my first bad print was my printer being totally out of alignment initially - there was a mechanical adjustment to the paper feed system and I had not run an alignment yet.
One can change the pixel size of the target, e.g. by 1 pixel (or more) to reduce the PPI by lowering the pixel count, yet print at the same output size. But that will activate the printer driver's resampling, which is of much lower quality than we can do. By only reducing the pixel count, and printing a proportional fraction smaller (keeping a constant 600 PPI), we will see the aliasing caused by Photoshop's resampling.
I would agree with that line of reasoning, but looking closely at the dots under 40x magnification, there is no splatter pattern around the dot? The dots are just not being fired as precisely as they should be, creating a blurry fuzz around what should be a clean edge. I have never been able to see the splatter from my printer's dots! Much too small. In my old tests I clearly observed issues with bidirectional printing affecting dot placement precision, affecting vertical line resolution and hurting the overall smoothness of the dither pattern.
I assume that the head travel speed is chosen to minimize any speed splatter on common media. It also ties into the dying/blending characteristics for multiple passes, so timing is probably carefully selected.
]Here is something curious. This is an image of the heading text from a banding adjustment pattern, which seems to be a 4 pass print mode or something like that, certainly not as many passes as Highest (max no. of passes). It may have been 7 passes. The text is much cleaner looking at the edges, proof that my iPF8400 is capable of very clean looking lines. For some reason when there is a lot to do in a pass, printing highly varying detail, over an increased number of passes using the highest quality mode, the dot precision gets all messed up when it comes to clean edges like text.
It's odd indeed. A long shot, but maybe a print from another application can make a difference? Could there be output dithering taking place by the Color Management system?
Cheers,
Bart
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Anyone try this using Qimage Ultimate and Photoshop CS6?
I got "wildly" different results even though the images both measure out to 5.118" sq. and 720ppi.
Here is a scan of them both, but they are strange to say the least! Same 3880 printer used. Head alignment done yesterday too.
Don't know why PS see the upper right square 14.2 as a B&W only. QI does better there.
I also did one on a 3880 with K7 Piezo inks and QTR. Had to convert it to B&W Gamma 2.2 TIFF and it was better, although some shadows in the vertical line areas of the outside blocks.
Well crap! Even Lightroom 5.7.1 prints differently than PS CS6 too. No B&W square like the image shown below at 14.2 in PS CS6 (Which is the only one of 4 programs to do that!).
Hi SG,
Thanks for that feedback. Maybe you're on to something, if Samuel is printing from PS (although at 600 PPI, so the frequency effects will be different).
Cheers,
Bart
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Anyone try this using Qimage Ultimate and Photoshop CS6?
I got "wildly" different results even though the images both measure out to 5.118" sq. and 720ppi.
Here is a scan of them both, but they are strange to say the least! Same 3880 printer used. Head alignment done yesterday too.
I just downloaded your scan jpegs, they are quite small but still very revealing. I do not think it is a head alignment issue at all.
First up Bart's target for Epson (360/720ppi) printers is not 720ppi - it is 719.988ppi. You need to resize without resampling to 720ppi for one.
If you failed to catch that, I suspect the different routes will treat that number differently depending on the numeric accuracy the driver can tolerate, or whether it truncates or rounds up the number to an integer value.
I was able to simulate similar (not identical) weird artifacts like in some of your scans of prints from PS CS6, Paintshop and Photostudio by downsampling Bart's target to 360ppi using 'Nearest Neighbor' resampling in PS. Anyway its pretty obvious from the aliasing pattern in those prints that it was not printed at 720ppi.
I think Roy has confirmed before on forums that QTR does not resize the image data at all, so the operating system likely takes care of that - which may explain to some extent why it looks so different from the others. Looks like bilinear resampling?
Lightroom looks weird, but it does resample before handing the data over to the printer driver, and uses a slightly better downsampling algorithm than Photoshop. Strange artifacts! If not for the smooth gray background it almost looks like a paper feed issue and printhead alignment problem in the star pattern, but since the reproduction of the smooth gray area looks perfect (the scan is too small to tell properly), I assume it is neither, and the other prints collude to agree that the printer is well aligned.
I have sample prints from an Epson 7900 printed from the driver out of PS CS6 of Bart's original camera resolution target, which I know is printed properly at 720ppi and I can safely say it should not look like any of the scans you are showing. The printer can resolve almost as well as my Canon (better in some respects), and the targets look identical when both printers are well aligned.
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Canon iPF is better at resolving fine details, so I'm afraid aligning won't help in this regard.
You may have misunderstood what I said? I agree that my Canon is better at resolving fine details (I don't own any Epson printer), but I can clearly see less than perfect alignment in my prints of Bart's target, and older prints of his camera resolution target show better alignment too, so I think I can do an even better job in the alignment of my Canon.
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The patterns you correctly point at are merely limitations of pixel size, which aren't small enough to depict gradients accurately. Having said that, I am working on generating even higher quality patterns, but they take a lot longer to calculate (processing time x 100) and then need to be composited into the various composite patterns. May take a while to complete.
Not mistakenly, they are supposed to be of equal density (especially the bottom two that run hor/ver), but gamma and profiling may play a trick on us, as well as the difficulty to exactly get intermediate tones from a limited number of inks through dithering. I do see the issue with aliasing patterns, the low frequency waves, and am looking for a way to solve that without compromising the detection sensitivity of errors. Maybe I need to change the overall gamma of the target, or use a different pattern than pure sinusoids (but that would probably need different settings for each dithering method). At the moment I'm calculating the patterns with much higher accuracy to see if that makes a difference. If not, more drastic changes may be needed.
Unfortunately, uniform contrast lines only allow fixed pixel resolution measurements, like 600 PPI = 11.81 cy/mm, 300 PPI = 5.91 cy/mm, 200 PPI = 3.94 cy/mm, 150 PPI = 2.95 cy/mm , 120 PPI = 2.36 cy/mm, 100 PPI = 1.97 cy/mm, and only in horizontal/vertical orientation. But those resolutions should be easy for any printer. It's mainly in the region between 300 or 360 PPi and 600 or 720 PPI that we will see the differences in e.g. media/ink diffusion, and there would be no info there without sinusoidal or other intermediate tones.
I think even in the most well aligned printers the hor/ver lines will print with different densities than the top two diagonal quadrants? But the hor/ver should print with the same density, and the two diagonals should print with the same density assuming all the stars align (bad pun)!
I'm still thinking about the usefulness of the sinusoidal patterns. The low frequency aliasing pattern make them difficult to read at first. Uniform contrast lines are extremely useful to determine issues with dot gain, ink bleed, dot precision etc., because you know they are supposed to be sharp lines. I think the rightmost column could be modified to include them, instead of the diagonal pattern. Those resolutions are very revealing for printers, don't overestimate them! In fact if not for the tiny pattern of hor/ver lines in the top left of your target, I would not have so conclusively determined I could align my print heads better. I also suspect that these inkjet printers have issues firing accurately in a pass depending on what colors/densities are printed in a pass sequence. Nero in another thread on printer linearization made some sort of discovery that indicated something like that I think.
I'm not sure I'm so concerned about detail between 300 and 600ppi or 360 and 720ppi. One has to resample to either size anyway - I want to know how accurately pixels at the highest resolution are rendered. I know my Canon can just about resolve a single pixel line at 600ppi on most gloss or matte media, and any halos will be visible under close scrutiny. I can even observe the mazing/zipper artifacts so common in raw files processed by Lightroom/Camera Raw!
But I am not saying the sinusoids are not useful! After better understanding how they work thanks to your explanations, I can now 'read' print head alignment issues separately from aliasing issues. Brilliant work Bart! This target is a Godsend :) YOU are a Godsend!
Good. Frankly, your profiling seems to be quite good.
Thank you! After spending many months refining and improving my profiling, I'm glad it has proved fruitful and earned your rare high praise :) I think top-notch profiles are still extremely difficult to make even with today's tools, but in general it has become somewhat easier, if one knows what to do. The commercial profiling packages are marketed to make them seem push-button easy to use, but are in fact more complicated than they appear. How is your profiling process coming along? Are you pleased with the measurements of your targets?
I assume that the head travel speed is chosen to minimize any speed splatter on common media. It also ties into the dying/blending characteristics for multiple passes, so timing is probably carefully selected.
It's odd indeed. A long shot, but maybe a print from another application can make a difference? Could there be output dithering taking place by the Color Management system?
I printed using the iPF Photoshop 16-bit Plug-in, which claims to ingest 16 bit data. If memory serves it dumbs it down to 12 bits before handing the data over to the printer - the printer's processor is only capable of dealing with 12 bits of precision. I'm not sure if Canon has updated the LCOA processor to work with 16 bits of data in the latest models. Anyway Photoshop does not work in all 16 bits of precision to start with. This info is several years old from Scott Martin. I am not entirely sure what is going on, but will continue to experiment and maybe get to the bottom of this fuzzy pattern issue. I suspect that text prints better with fewer number of passes. The Highest (max. no. of passes) is more like a special photo mode for the smoothest dither and most uniform dot coverage, and sharp photographic detail. It may not be optimized for fine text and lines. I note that there is a checkbox in the plug-in that is called 'high precision text and fine lines' which may make a difference. I'll look again at my old test prints using this setting.
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I just downloaded your scan jpegs, they are quite small but still very revealing. I do not think it is a head alignment issue at all.
First up Bart's target for Epson (360/720ppi) printers is not 720ppi - it is 719.988ppi. You need to resize without resampling to 720ppi for one.
If you failed to catch that, I suspect the different routes will treat that number differently depending on the numeric accuracy the driver can tolerate, or whether it truncates or rounds up the number to an integer value.
I was able to simulate similar (not identical) weird artifacts like in some of your scans of prints from PS CS6, Paintshop and Photostudio by downsampling Bart's target to 360ppi using 'Nearest Neighbor' resampling in PS. Anyway its pretty obvious from the aliasing pattern in those prints that it was not printed at 720ppi.
I think Roy has confirmed before on forums that QTR does not resize the image data at all, so the operating system likely takes care of that - which may explain to some extent why it looks so different from the others. Looks like bilinear resampling?
Lightroom looks weird, but it does resample before handing the data over to the printer driver, and uses a slightly better downsampling algorithm than Photoshop. Strange artifacts! If not for the smooth gray background it almost looks like a paper feed issue and printhead alignment problem in the star pattern, but since the reproduction of the smooth gray area looks perfect (the scan is too small to tell properly), I assume it is neither, and the other prints collude to agree that the printer is well aligned.
I have sample prints from an Epson 7900 printed from the driver out of PS CS6 of Bart's original camera resolution target, which I know is printed properly at 720ppi and I can safely say it should not look like any of the scans you are showing. The printer can resolve almost as well as my Canon (better in some respects), and the targets look identical when both printers are well aligned.
This is interesting. I suspect you are right in that the math involved in the editing software is having an effect, especially in the 14.2 square area where it goes to full black in Zoner software to B&W in PS since both use the Epson driver. QTR also does some odd effects in that area as well even though it does not use the Epson driver. Hard to see in the Lightroom that the gray has a reddish tinge to it even though the ICC was off in the Epson driver. Why the reddish tinge escapes me when it doesn't show in the others. LR handles this very differently than PS even though they use the Epson driver.
Qimage has the smoothest tonality so it may handle the math better than the others. I did have the Sharpness turned to "Off" since it uses about a dozen different sharpening methods in the menu. The "Help" in it says "Vector Sharpening" may be the sharpest, but I didn't go that far. It has other sharpening methods like Hybrid, Fusion, etc. as well and they all might produce a different look in the end. I'll probably stay with it as it seems to work the best for me. The others are very odd in the outcome with the 14.2 square as well as the diagonals in the 8 area on the right with some. CS6 seemed to produce the finest line detail, but the 14.2 was too disturbing as well as the 8 diagonals.
Interesting test though, but somewhat scary too since the software can really ruin an image as with the B&W squares in 14.2 from the heavy-editing softwares show. What effect this has does during a normal printing is unknown.
I'm sort of suspicious of the PNG format as it does some compression that may be playing into this when it uncompresses by the sundry software. PNG may be an act of compromise and leading to the different outcomes? Maybe an uncompressed TIFF would be better? I know I had to save the PNG file as a TIFF in Gamma 2.2 for the K7/QTR image which appears better than the other editors images which were all PNG.
I might take one to my pro lab and see what mess they generate. They use a Mac with a RIP and I use Windows. Don't know if the math is the same between them and the final outcome.
SG
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First up Bart's target for Epson (360/720ppi) printers is not 720ppi - it is 719.988ppi. You need to resize without resampling to 720ppi for one.
Hi Samuel,
I missed that, sorry, because I specifically changed the PPI tag to 720 before saving and assumed it was as instructed. I've done that again, checked that the tag now says 720, and uploaded the image again for future downloads.
And checking it again, the tag was changed once more, presumably because Photoshop doesn't know how to deal with 130mm, 3685 pixels, and then calculates the PPI from there (which then becomes 719.9923077 PPI, and not what Photoshop makes of it), instead of accepting the user's input for the PPI tag field. When is an international company like Adobe going to adopt the worlds standard units of measurement, or is it a TIFF conventions thing (also Adobe owned)? PNGs should just do what they are told, but the PPI tag is already changed by Photoshop.
Anyway, a decent printing application should ignore the tag anyway, and use the output size as specified by the user, or 100% of the pixel dimensions, or use an enforced PPI setting.
Interesting what such a test target can reveal.
Cheers,
Bart
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Bart, do you have this file as a TIFF? As I read it, the PNG (even PN-24) is an 8 bit and the TIFF is larger 16 bit.
Perhaps the 8 bit math is doing something within the software resulting in the sundry software outcomes against a 16 bit file? I don't know why the PNG > TIFF conversion seemed to work better in K7/QTR. If QTR did PNG, no doubt it would be a different result than the converted to TIFF one.
SG
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I think even in the most well aligned printers the hor/ver lines will print with different densities than the top two diagonal quadrants? But the hor/ver should print with the same density, and the two diagonals should print with the same density assuming all the stars align (bad pun)!
I agree, not about the pun but, what is most important to look for is asymmetry, like between the horizontal and vertical cycle areas, or between the two diagonal cycle patterns. I am at the moment busy (between regular work) with improving the sinusoidal patterns even more, because I think they can still add a lot of insight, but I want them to be as flawless as possible and certainly not the weakest link. The recalculation of the patterns now takes much(!) longer though, so I only get output presented by the computer (cooling fans are working hard, and all CPU cores are kept busy) for further editing/compositing every once in a while. Hopefully I can also reduce the difference between diagonal and horizontal/vertical cycles, so they don't distract as much.
I'm still thinking about the usefulness of the sinusoidal patterns. The low frequency aliasing pattern make them difficult to read at first. Uniform contrast lines are extremely useful to determine issues with dot gain, ink bleed, dot precision etc., because you know they are supposed to be sharp lines. I think the rightmost column could be modified to include them, instead of the diagonal pattern. Those resolutions are very revealing for printers, don't overestimate them! In fact if not for the tiny pattern of hor/ver lines in the top left of your target, I would not have so conclusively determined I could align my print heads better. I also suspect that these inkjet printers have issues firing accurately in a pass depending on what colors/densities are printed in a pass sequence. Nero in another thread on printer linearization made some sort of discovery that indicated something like that I think.
I'll have to see where it takes us, and if the aliasing can be traced to what's causing it. The sinusoids have several very interesting properties, and some of those have not been addressed yet. It has to do with upsampling and how the top left pattern (11.8 or 14.2 cy/mm depending on the PPI version) gets rendered. The higher resolution diagonals may look a bit funky at close inspection of the original on display, but they turn into (almost) perfect sinusoids when properly upsampled.
I'm not sure I'm so concerned about detail between 300 and 600ppi or 360 and 720ppi. One has to resample to either size anyway - I want to know how accurately pixels at the highest resolution are rendered.
I understand, but to judge resampling we need a predictable pattern that needs to look exactly the same as the original, only at a different size. If the pattern is not predictable, or not as 'organic' as a regular image but has only straight lines, then the challenge is a rather different one, and maybe easier (when less intermediate color blending/dithering is required).
But I am not saying the sinusoids are not useful! After better understanding how they work thanks to your explanations, I can now 'read' print head alignment issues separately from aliasing issues. Brilliant work Bart! This target is a Godsend :) YOU are a Godsend!
Blush... Well, I try to make a small contribution, regardless of who sent me or not.
Thank you! After spending many months refining and improving my profiling, I'm glad it has proved fruitful and earned your rare high praise :) I think top-notch profiles are still extremely difficult to make even with today's tools, but in general it has become somewhat easier, if one knows what to do. The commercial profiling packages are marketed to make them seem push-button easy to use, but are in fact more complicated than they appear. How is your profiling process coming along? Are you pleased with the measurements of your targets?
Slowly getting there. The prints are dry, but I haven't had the time to let i1Profiler do its job yet. Another printer is running low on ink, so I want to preserve that for actual image prints for the moment (note to self, need to order some new ink as well).
And then there are comparisons needed between different printing applications, Qimage and Photoshop/Lightroom for example, to see if and what is different.
I printed using the iPF Photoshop 16-bit Plug-in, which claims to ingest 16 bit data.
I understood that, but maybe the application that sends it data to the printer driver/plugin already does something we do not want.
Cheers,
Bart
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Bart, do you have this file as a TIFF? As I read it, the PNG (even PN-24) is an 8 bit and the TIFF is larger 16 bit.
Hi SG,
Yes, the original is a Photoshop (15-bit) multi-layer TIFF, and when flattened it may be larger than the PNG, depending on the level of backwards compatible compression (not all applications can read compressed TIFF files). The PNG version is 16-bit, but uses very efficient loss-less compression, and doesn't carry as much metadata in its header. I'm currently revising parts of the targets, 'bit' by 'bit', so once I'm done I'll upload a TIFF version, but I don't think it will make any difference to the data itself.
Perhaps the 8 bit math is doing something within the software resulting in the sundry software outcomes against a 16 bit file? I don't know why the PNG > TIFF conversion seemed to work better in K7/QTR. If QTR did PNG, no doubt it would be a different result than the converted to TIFF one.
Well, that's part of what the test is for. Some applications, e.g. Qimage, will convert to 8-b/ch data if 16-b/ch input is read in and it will dither the data to hide errors that may be caused by that conversion. If 8-b/ch data is input, nothing will be changed. So that is already a test, because e.g. Lightroom can send both, either 8-b/ch or 16-b/ch. Do they render the same?
That's the reason I made it a 16-b/ch test target, despite the fact that there are only a few 16-bit print pipelines available (e.g. Canon's XPS printer drivers on Windows). There may be RIPs that handle 16-bit data, so I wanted to have the capability to test that. One can always save an 8-bit/channel version of the target and then print both versions through the same driver configuration.
Cheers,
Bart
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Qimage has the smoothest tonality so it may handle the math better than the others. I did have the Sharpness turned to "Off" since it uses about a dozen different sharpening methods in the menu. The "Help" in it says "Vector Sharpening" may be the sharpest, but I didn't go that far. It has other sharpening methods like Hybrid, Fusion, etc. as well and they all might produce a different look in the end. I'll probably stay with it as it seems to work the best for me. The others are very odd in the outcome with the 14.2 square as well as the diagonals in the 8 area on the right with some. CS6 seemed to produce the finest line detail, but the 14.2 was too disturbing as well as the 8 diagonals.
Yes, you'll need to disable all resampling and output sharpening, and tell Qimage that the target should be printed as intended 130x130mm @ 600 or 720 PPI, depending on the version. The printer driver should also not attempt to print borderless, because that causes the printer driver to again resample the image to slightly larger than the paper and overspray the edge of the selected page size.
Interesting test though, but somewhat scary too since the software can really ruin an image as with the B&W squares in 14.2 from the heavy-editing softwares show. What effect this has does during a normal printing is unknown.
Well, fortunately, normal images are much more forgiving. I did want to have the target point out any irregularities that the print pipeline may introduce, or the printer alignment may cause. From there on things should be relatively easy.
I'm sort of suspicious of the PNG format as it does some compression that may be playing into this when it uncompresses by the sundry software. PNG may be an act of compromise and leading to the different outcomes? Maybe an uncompressed TIFF would be better? I know I had to save the PNG file as a TIFF in Gamma 2.2 for the K7/QTR image which appears better than the other editors images which were all PNG.
PNG should not make a difference, but we'll see when I'm a bit further with some edits.
I might take one to my pro lab and see what mess they generate. They use a Mac with a RIP and I use Windows. Don't know if the math is the same between them and the final outcome.
A lot depends on the equipment they use, and the settings that the operator/RIP uses. Allow me to tweak the target a bit more before you do, so everybody is using the same level of sophistication.
Cheers,
Bart
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Yes, you'll need to disable all resampling and output sharpening, and tell Qimage that the target should be printed as intended 130x130mm @ 600 or 720 PPI, depending on the version. The printer driver should also not attempt to print borderless, because that causes the printer driver to again resample the image to slightly larger than the paper and overspray the edge of the selected page size.
Well, fortunately, normal images are much more forgiving. I did want to have the target point out any irregularities that the print pipeline may introduce, or the printer alignment may cause. From there on things should be relatively easy.
PNG should not make a difference, but we'll see when I'm a bit further with some edits.
A lot depends on the equipment they use, and the settings that the operator/RIP uses. Allow me to tweak the target a bit more before you do, so everybody is using the same level of sophistication.
Cheers,
Bart
Okay. I'll wait before I bug my local print shop.
I also noticed Qimage did not allow me to set up for anything more than 360 DPI in the right pane for the Epson (No ability to set 720 DPI I found?). However, when I set the PNG image size in "Custom" to 5.118 x 5.118 inches, the info box overlaid on the image showed "720DPI Excellent." Seems it is doing its own sharpening internally for the Epson prior to getting to the driver.
SG
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Okay. I'll wait before I bug my local print shop.
I also noticed Qimage did not allow me to set up for anything more than 360 DPI in the right pane for the Epson (No ability to set 720 DPI I found?).
The Epson printer driver needs to have the 'finest detail' option activated, otherwise it cannot process the 720 PPI data and it will resample to 360 PPI without warning (and use poor resampling quality to do so). Qimage will warn you about that.
However, when I set the PNG image size in "Custom" to 5.118 x 5.118 inches, the info box overlaid on the image showed "720DPI Excellent." Seems it is doing its own sharpening internally for the Epson prior to getting to the driver.
Depends on where you see that. A the top right there is a page layout preview which will also give feedback about the PPI that the printerdriver is expecting (usually 300x300/600x600 or 360x360/720x720). Make sure that you can use the highest resolution that the printer is capable of. When you hover the mousepointer over the preview you'll get some feedback for the particular image you are previewing. At the bottom of the page there is a status line with feedback about output size and PPI/profile/ etc.
Cheers,
Bart
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I found a comment about the 720 (or not) PPI tag as it gets corrupted in Photoshop on the ImageMagick page (http://www.imagemagick.org/script/command-line-options.php#density)
It basically states:Note that Photoshop stores and obtains image resolution from a proprietary embedded profile. If this profile is not stripped from the image, then Photoshop will continue to treat the image using its former resolution, ignoring the image resolution specified in the standard file header.
Next additional endeavor is to find out how to strip the proprietary Photoshop profile ...
Until then, when using Photoshop to print the target, it may be difficult to get exactly 720 PPI output, unless perhaps a printer driver is sensible enough to ignore the tag, and rely on output size and number of pixels.
Cheers,
Bart
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I just printed the 600dpi target with photoshop 6 on my HPZ3100 and it looks OK- some small problems but nothing to worry about.
(When opened 'Image Size " in Photoshop it read 600dpi so i geuess that part worked well..)
Bart, thank you for providing the target!
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I just printed the 600dpi target with photoshop 6 on my HPZ3100 and it looks OK- some small problems but nothing to worry about.
Hi Pieter,
Good news, that's what we aim for, no problems ... But it is also nice to have that objectively confirmed.
(When opened 'Image Size " in Photoshop it read 600dpi so i guess that part worked well..)
Yes, the 600 PPI version seems to be no problem for Photoshop, it can figure it out correctly. On the other hand, 720 PPI remains an odd nuisance to solve. Also placing it on a larger canvas doesn't solve it, or I haven't found the preferred dimensions yet.
Bart, thank you for providing the target!
Graag gedaan.
Cheers,
Bart
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Bart, if the target was saved as a tiff, the ppi setting of either 600 or 720 remains sticky. Looks like you have discovered something weird about the way PNGs are tagged with the image resolution value. What a funny problem, but also a very serious one. The 600ppi PNG target still opens as 599.999 ppi instead of 600ppi in Photoshop CS6 for me. I'm not sure how kers and you got it to show up as 600ppi. I'm going to resave them as tiffs for now...
I think you have partially won me over to the use of sinusoids in your printer target. I agree they are useful, and uniform high contrast pixel lines cannot reveal the full story. I will pay close attention when you post examples from your printers and comment about them. I am curious to know what other issues these patterns can reveal. I just tried resampling the target in Photozoom Pro, it did not give a near perfect sinusoid rendering of the patterns but rather enlarged (obviously lol) and made the low frequency aliasing patterns a great deal more apparent. It is only these patterns that are irritating me at the moment - one needs to learn what patterns are representative of the actual data in the target, (just at a different size like you said) and what patterns indicate resampling, or misalignment or additional sharpening or dithering effects etc.
Can't even imagine the computational load these sinusoidal calculation require! May I say a big thank you for Above 5 cycles/mm frequency, it looks like the printer is unable to perfectly resolve the sinusoidal patterns, partly due to dot size, partly due to the density of the inks.
I am not sure how looking at the printed target could reveal that the printer pipeline is capable of 16 bits precision? Assuming no dither was applied in the process.
Allow me to tweak the target a bit more before you do, so everybody is using the same level of sophistication.
Excellent! I will wait patiently until then.
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Bart, if the target was saved as a tiff, the ppi setting of either 600 or 720 remains sticky.
Indeed Samuel, I also found that out this morning.
Looks like you have discovered something weird about the way PNGs are tagged with the image resolution value. What a funny problem, but also a very serious one. The 600ppi PNG target still opens as 599.999 ppi instead of 600ppi in Photoshop CS6 for me. I'm not sure how kers and you got it to show up as 600ppi. I'm going to resave them as tiffs for now...
I've uploaded two new (tweaked) versions, as TIFFs, and on my computer they open in Photoshop CS6 with the intended/correct PPI indication. The links in the original post have been adjusted to point to the new TIFF versions. While there is nothing wrong with losslessly compressed PNGs per se, apparently Photoshop uses some strange(?) logic that messes up the PPI tags in PNGs but not in TIFFs, at least at these specific sizes.
Here are the links to the updated/tweaked TIFF versions, I'll remove the PNGs to avoid confusion:
Test target for 600 PPI printers (https://www.dropbox.com/s/zzh73f3g4rwd4c5/PrintRes_130mm_600PPI.tif?dl=0) (e.g. Canon / HP)
Test target for 720 PPI printers (https://www.dropbox.com/s/0g5j2j7nmjdt0zp/PrintRes_130mm_720PPI.tif?dl=0) (e.g. Epson)
I've used ZIP compressed TIFFs that may not be readable in software that uses non-standard or old TIFF libraries. If that poses any problems I will change that to much larger uncompressed versions, and put them in ZIPped archives.
The current tweaks are mostly about an even higher quality of the sinusoidal patterns with the 4 quadrants of uniform period. I also attempted to reduce the difference in average density of the horizontal/vertical and diagonal patches of the highest possible resolution, at the top left corner. The higher quality should reduce the chance of aliasing when everything else is perfect even further. Any printed misalignment should therefore still stick out as a sore thumb, and only be caused by that misalignment, or by resampling and sharpening.
The other patterns in the target will be reviewed and possibly adjusted/tweaked at a later stage, but for the sinusoidal based ones that would take an enormous amount of computation time because they are larger in size.
I think you have partially won me over to the use of sinusoids in your printer target. I agree they are useful, and uniform high contrast pixel lines cannot reveal the full story. I will pay close attention when you post examples from your printers and comment about them. I am curious to know what other issues these patterns can reveal.
The sensitivity of minute misalignments/distortions that manifest themselves as significant aliasing artifacts is used in other fields as well. It can be used in accurate angle measurements with mechanical inclinometers, or for measuring dimensional expansion or contraction. It is somewhat related to the higher accuracy one can achieve with using Vernier calipers (https://en.wikipedia.org/wiki/Calipers#Vernier_caliper) for distance measurements, and the Vernier acuity which we can exploit by printing at 600 or 720 PPI instead of lower settings. While normal visual acuity is on average often limited to something like 300 to 360 PPI, we are able to see much higher resolution when Vernier acuity is taken into consideration.
We can use the properties of moiré patterns (https://en.wikipedia.org/wiki/Moir%C3%A9_pattern) to search for the cause and magnitude of the misalignments. The simplest is the head alignment and paper travel alignment which should produce similar density in the horizontal/vertical sinusoids, but there may also be issues with paper that is not fed squarely but at a slight angle due to some slippage or uneven friction.
I just tried resampling the target in Photozoom Pro, it did not give a near perfect sinusoid rendering of the patterns but rather enlarged (obviously lol) and made the low frequency aliasing patterns a great deal more apparent. It is only these patterns that are irritating me at the moment - one needs to learn what patterns are representative of the actual data in the target, (just at a different size like you said) and what patterns indicate resampling, or misalignment or additional sharpening or dithering effects etc.
Yes, PhotoZoom Pro will accentuate high contrast edge detail by adding resolution where there was none before. When measured accurately, the resolution that is created, e.g. by upsampling to 600 or 720 PPI, exceeds that which was available in the original file. While that may show as a bit strange on the test target because that level of detail was not present in the original sinusoids, it works very well on natural images which are obviously much more random/organic (and noisy) than these mathematical constructions. Down-sampling in PhotoZoom is not very good, but for upsampling the results can hardly get better.
Can't even imagine the computational load these sinusoidal calculation require! May I say a big thank you for Above 5 cycles/mm frequency, it looks like the printer is unable to perfectly resolve the sinusoidal patterns, partly due to dot size, partly due to the density of the inks.
Well, the sinusoids are not the hardest part, but the way we point sample or area sample at the pixel level can be computation intensive. But that's what we have computers for. All we have to do is be patient while the calculations are running. I don't think printers or cameras will be able to get it 100% accuretely, unless we can use much higher resolutions. But that's not very practical given all the other variables like paper transportation and color dithering, and bandwidth limitations when sending the print-data.
I am not sure how looking at the printed target could reveal that the printer pipeline is capable of 16 bits precision? Assuming no dither was applied in the process.
Other than comparing the output of an 8-b/ch and a 16-b/ch version of the target, I'm not sure either. I may need to add another tricky pattern to the target to amplify those differences. There may be some utility in the two (1, 2, 3 line wide) patterns at the top right and bottom right of the neutral star background, and the steps in the gradient. Of course colour dithering is also something that can benefit from 16-bit print pipelines, and those tonalities are more vaguely related to resolution.
Cheers,
Bart
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Hi Bart,
Also the 720 ppi target seems to be OK - it reads in CS6 -image size - 720dpi as it should.
The only thing i see that is different in this target is that it is compressed 1:4 and the 600dpi is not.
Maybe the problem arises with decompression? in some cases...
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Hi Bart,
Also the 720 ppi target seems to be OK - it reads in CS6 -image size - 720dpi as it should.
The only thing i see that is different in this target is that it is compressed 1:4 and the 600dpi is not.
Maybe the problem arises with decompression? in some cases...
Hi Pieter,
I think that the TIFF versions at least take a way the uncertainty of the PPI tag that's shown in the Resize dialog. We do not want any resampling influence that's interfering with the analysis of whatever the printer does. As long as the file is read as it was saved, we should be fine. Of course the 600PPI version has fewer pixels, and lower resolution, so it might compress better (depending on how Adobe implemented things...).
Cheers,
Bart
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Bart, I tried the new compressed 720 TIFF on the Epson. I don't see any difference between my newly printed images (Page 2 here, Test_01.jpg) from the PS CS6 and Ultimate Image made prior.
I still see that odd banding around 8 and the white to black in the upper left corner box of the CS6 and not in the QU one. QI is smoother overall (All sharpening set to OFF), but the PS CS6 version shows more distinct lines (sharper) overall. CS6 does show the moire patterns, but QI does not. QI does something different than CS6 prior to hitting the Epson print driver.
Aside, when I opened the file in PaintShop Pro X6 and zoomed in to the 8 area, I changed the colors to 2 just to see the B&W lines. They are all of a different width: Some two, some 4, some 3 and spacing is irregular too. Seems very odd, but might explain why I seem to have issues in that area out of the 'Editing' softwares (i.e. PS CS6, PaintShop Pro, etc.)
Add:
I just tried a print using QI cranked up to full sharpness (20, and "Fusion") and 360 DPI (Which on the rollover in the right pane shows 720 DPI Excellent.). I do see the moire and more lines, although they are splotchy and do seem uneven in widths as alluded to above. It does not show the black & white square in the CS6 version in the upper left and is far more even than CS6.
Something about the unevenness of the line widths might be an issue. Don't know if it is the software, computer OS (Windows 8.1 64x), computer math library, or where those issues come into play.
SG
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Bart, I tried the new compressed 720 TIFF on the Epson. I don't see any difference between my newly printed images (Page 2 here, Test_01.jpg) from the PS CS6 and Ultimate Image made prior.
Hi SG,
In a way that is good. If it had made a difference then that would mean that the target had generated the aliasing, in this case any aliasing is totally due to 'other' causes. I'm preparing (between other activities) a write-up about how to interpret aliasing as it may manifest itself on the different patches and the star.
I still see that odd banding around 8 and the white to black in the upper left corner box of the CS6 and not in the QU one. QI is smoother overall (All sharpening set to OFF), but the PS CS6 version shows more distinct lines (sharper) overall. CS6 does show the moire patterns, but QI does not. QI does something different than CS6 prior to hitting the Epson print driver.
Qimage does several things to avoid problems, and that is before and after any resampling or sharpening (which you have disabled as it should be for this target) is used. One thing is that it adds dithering when 16-bit/channel data files are read (it does nothing if 8-b/ch input is read). This will visually smoothen gradients because posterization due to rounding errors is broken up, as if the file has 8.5-b/ch data after conversion to 8-b/ch. It is slightly better able to follow the slope of a gradient, and that goes for the smoothly varying sinusoids as well. Busy areas already have so much detail that the dithering will not change anything significant. Then after potential resampling, profile colorspace conversion, and output sharpening, it optionally (check your settings) will do another round of dithering, to break up things that e.g. got posterized after profile conversion. It does all that at the 600 or 720 PPi level, so too small to ever become visible at normal viewing distances.
What Photoshop does is anybody's guess, but apparently it is not helping to cover up any print pipeline issues, and maybe adds some itself. The Adobe Color Management sytem e.g. adds a linear slope to shadows and thus modifies the tone curve. It may also do something to the document dimensions, in concert with the printer driver (and can thus be different between Mac and Windows operating systems). We saw what happened to the PPI tag in PNGs, I didn't know it did that, and who knows what else is going on.
Aside, when I opened the file in PaintShop Pro X6 and zoomed in to the 8 area, I changed the colors to 2 just to see the B&W lines. They are all of a different width: Some two, some 4, some 3 and spacing is irregular too. Seems very odd, but might explain why I seem to have issues in that area out of the 'Editing' softwares (i.e. PS CS6, PaintShop Pro, etc.)
No, that's perfectly normal. It is not possible to render half or part of a pixel in a continuous tone image, so it rounds full pixels up or down when only 2 colors are available. Only the highest resolution patch at the top left has a bi-tonal horizontal/vertical cycle. When there is a minute resizing (alignment or physical file resizing) involved then that area will develop waves. If the issue is not symmetrical, then one will be darker than the other, or have a different wave distance/frequency.
Pure white or black in the top left hor/ver cycles, suggests exactly half resolution, by using a very poor downsampling algorithm. A good algorithm would produce medium gray (half white, half black), but e.g. nearest neighbor would pick every other line (black/black or white/white) and drop the other. Make sure you have the 'finest detail' option switched on in the Epson printer driver when printing from Photoshop. Qimage remembers earlier driver selections for specific media.
Cheers,
Bart
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Add:
I just tried a print using QI cranked up to full sharpness (20, and "Fusion") and 360 DPI (Which on the rollover in the right pane shows 720 DPI Excellent.). I do see the moire and more lines, although they are splotchy and do seem uneven in widths as alluded to above. It does not show the black & white square in the CS6 version in the upper left and is far more even than CS6.
Something about the unevenness of the line widths might be an issue. Don't know if it is the software, computer OS (Windows 8.1 64x), computer math library, or where those issues come into play.
No, the target is 720 PPI. So when you print at 360 PPI, then line detail will need to be merged into single pixel/line detail. Qimage uses a much better downsampling method, with added anti-aliasing (amount is user selectable), and thus avoids resampling errors better.
The target for 720 PPI printers should be printed as 720 PPI. Any remaining aliasing will then be due to alignment issues. When the target is resampled then you'll get a combination of resampling and alignment issues.
Cheers,
Bart
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Redid this thing in CS6 using the following:
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PrintRes_130mm_720PPI.tif Image opened in CS6.
File > Print
(Opens PS Print Setting's pane)
Select printer (My case, Epson Stylus Pro 3880 as I have sundry printers Windows sees.).
"Main" tab shows:
Click on "Print Settings" which shows the Epson driver selection pane.
Media type: Premium Photo Paper Glossy (What I have)
Color: Color
Print Quality: Select "Quality Options" > Quality Options pane opens.
Move Speed to #5
Print Quality: SuperPhoto - 2880x1440dpi
MicroWeave: On
Edge Smoothing unchecked. (This may be checked on by default?)
Uncheck High Speed
Select only "Finest Detail" (and this is not activated by default?)
Select OK
Mode:
Select Custom > Off (No Color Adjustment)
Letter 8 1/2 x 11 in.
Borderless is unchecked.
Go to "Page Layout" tab in the Epson driver.
Uncheck "Optimize Enlargement" if it is checked.
OK
Back in CS6 "Photoshop Print Settings."
Color Handling: Printer Manages Colors.
Position and Size: > Check "Center"
Scaled Print Size:
Scale 100% Height 5.118 Width 5.118
Scale to Fit Media: Unchecked
Print Selected Area is unchecked.
All other drop down arrows are unchecked (i.e. Printing Marks, Functions, PostScript Options Disabled.)
Press "PRINT" (and pray!...)
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Interesting that the banding that I saw in my first run around 8 now has moved up to 10 and not as bad. Also, the black and white I see in the upper left in priors is now gone and a smoother gray like QI was doing! It is sharper than QI now too, although QI still seems smoother overall.
The trick might be in the bolded area above? ("Finest Detail" which is not on by default in the Epson driver pane, or maybe the "Optimize Enlargement" which is checked by default?)
Interesting test though, if for nothing more than to learn your printing software better and also setting up the Epson printing driver which may not be optimum out of the box.
SG
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Interesting that the banding that I saw in my first run around 8 now has moved up to 10 and not as bad. Also, the black and white I see in the upper left in priors is now gone and a smoother gray like QI was doing! It is sharper than QI now too, although QI still seems smoother overall.
The trick might be in the bolded area above? ("Finest Detail" which is not on by default in the Epson driver pane, or maybe the "Optimize Enlargement" which is checked by default?)
BINGO!
If 'Finest detail' is not checked, the Epson printer driver will cause a down-sample to 360 PPI, and use a very poor resampling algorithm (seems to be Nearest Neighbor, yuck!!).
Interesting test though, if for nothing more than to learn your printing software better and also setting up the Epson printing driver which may not be optimum out of the box.
Correct, and some residual aliasing is almost unavoidable, because we are really pushing for the limits with a super sensitive pattern. Nothing is perfect, but that doesn't mean we shouldn't attempt to get as close as feasible. Also double-check if Qimage knows that that option must be switched on in the Epson printer driver (it'll show (720x720) above the page preview, and (600x600) for Canon printers). It should remember it for the ink/paper medium you use.
Cheers,
Bart
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Just to let you know that the targets were updated slightly. The right hand side 45 degrees rotated sweep, from 2 cycle/mm to 80% of maximum print resolution, was technically improved. Nothing was materially changed, I only improved its accuracy, which may look like it gets slightly darker (it's actually slightly lower contrast, less paper white) towards the highest spatial frequencies.
So, aliasing is even less likely caused by the target patterns, but more likely by alignment issues. The ability to resolve fine details is still a function of driver settings and paper/ink diffusion.
Cheers,
Bart
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Thanks Bart! I have downloaded the targets and looked at them, the sinusodial patters look to be of much better quality on screen. I have not had the time to make any new tests yet. I'm glad you made them into Tiffs. I also note that ZIP compression for Tiffs is extremely efficient, way better than compression for PNG files. And no more ppi issues! Yay! This is going to be my reference target for all future tests, and also a quality control target before making new tests, and also printing profile targets. One thing that I have yet to test is the consistency across a 44 inch roll. Is the printer consistent enough across its entire width?
Most curious to see what you managed to pull off with your printers. What are you printing with?
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Most curious to see what you managed to pull off with your printers. What are you printing with?
Still working on it, or planning to. I'm currently very busy with an assignment that involves shooting a lot of different products, and those images will need to be used on webpages, so no prints required for that. For quick limited size work I use desktop Canon printers (including a Pro-9500 II, I really like to use Canson Infinity Baryta Photographique on it), large format work is outsourced to some 4 different organizations, depending on requirements, and they use Durst Lambda's and/or Epson LF printers or Canon LF printers, and one uses a Roland printer for outdoor signage. So it's a little bit of everything, which is why I like to compare actual performance to keep them on their toes ...
One of these days I hope find some time to finish reprofiling one of my other printers which I have some issues with, so it'll be interesting to see what I can discover with the resolution target.
Cheers,
Bart
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With the newest TIFFs my odd looking slanted bands moved up from 8 into the 10 area on the right page (In my images posted prior.). Also, the pure white and black in the upper right is now smoother and gray tones (Not the stark B&W prior.). So something changed in the new iteration.
I do seem to seem more lines going into the middle of the circular target as well. Qimage still seems to be the best for even tonality over PS though. PS CS6 seems slightly more contrasty which leads to an apparent sharpness increase.
My own printer seems to show a slight magenta offset in the head alignment under high magnification (Like some CA issue in a camera.). I used the Auto setting in alignment, but maybe doing it Manually might be better (Although i get into self-doubts in Manual examination at times: Is the other number better than this one? Potshot.).
Interesting endeavor though and helps one learn how sharp - or not - their printer is.
Thanks Bart.
SG
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With the newest TIFFs my odd looking slanted bands moved up from 8 into the 10 area on the right page (In my images posted prior.). Also, the pure white and black in the upper right is now smoother and gray tones (Not the stark B&W prior.). So something changed in the new iteration.
I do seem to seem more lines going into the middle of the circular target as well. Qimage still seems to be the best for even tonality over PS though. PS CS6 seems slightly more contrasty which leads to an apparent sharpness increase.
Hi SG,
It sounds like something else changed as well on your side, because e.g. the middle region towards the circles (the star and the circles) is unchanged between target versions. Only the numbered patches and frequency sweep were improved a bit (fractionally smoother and more accurate), and it is now a TIFF file (to avoid issues with the puzzling Adobe PPI tag in PNGs). The fact that you moved from 8 into 10 cy/mm is very nice, but may be caused by the same thing that changed the printing of the unchanged center region. Maybe the (Adobe RGB) profile that was embedded in the PNG wasn't picked up for some reason, or lead to other Adobe creativity with the data. TIFFs are apparently better understood. The (16 to 8-bit/ch) dithering that Qimage uses may lead to smoother gradients anyway, because it virtually adds half a bit to the 8-bit pipeline, without affecting resolution in a negative way.
My own printer seems to show a slight magenta offset in the head alignment under high magnification (Like some CA issue in a camera.). I used the Auto setting in alignment, but maybe doing it Manually might be better (Although i get into self-doubts in Manual examination at times: Is the other number better than this one? Potshot.).
Interesting endeavor though and helps one learn how sharp - or not - their printer is.
Yes, focusing on one aspect -resolution- has its benefits, and it helps to have an objective quantification as well. Aiming for a moving target makes the process less predictable, and these cycles/mm are fixed goals. Because it is greyscale, color deviations are easier to spot. The gradient at the bottom, in the smoothest part at the bottom anyway, will also show how good the profile is at rendering greyscales with color ink.
Cheers,
Bart
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Yeah, I need to revisit the Manual head alignment at some point vs. the Epson Auto mode.
Not knowing how Epson does their Auto alignment, nor knowing what inks and placement of the ink on the head's ports is another matter. In manual, the targets seem small to what the head is capable of and maybe something there too as the head is about an inch tall vs. the tiny target of maybe 1/4" sq. Don't know. Their manual is sort of sketchy on manual too.
I'm not that sure of the paper thickness that Epson uses either transfers that well to the software/driver. I can use a digital micrometer and set the thickness, but if I set a thick paper I might get a head strike or hear the "clop-clop" drag of it on the paper even if I set the paper thickness in the driver. Perhaps any paper swells or edge curl and then so goes any alignment. Words like Narrow, Normal, Wide, Wider, Widest and Auto are often guesses too. I know I need to set a lot wider number based on what the mike tells me too, and not all that linear either (Else "Clop-Clop" sounds.)
Probably whatever I now use is "Good enough for an Epson." Might not print on the head of a pin worth a damn though. ;)
SG
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Together with your target, I've put in the resolution test image from the bottom of this page, http://www.clarkvision.com/articles/printer-ppi/ (http://www.clarkvision.com/articles/printer-ppi/).
Printing on a Canon Pro-1000 at 600 dpi on a high-glossy paper, I notice I cannot separate 1 pixel bars (the tiniest) from clarkvisions test image, on vertical lines that is (running up/down, perpendicular to print head movement axis) - on horisontal lines they are easy to distinguish. Does that indicate the need for a head alignment (and not feed adjustment)?
Tried unidirectional printing, and that helps precision / edge separation of vertical lines.
Printer is almost new, and had a head alignment on the paper included for the task at initial setup, and has printet very little amounts yet. Perhaps head alignment needs to be paper / media type specific (guess it'll only have on alignment saved though, even it could make sense per media type / head gap).
Also notice that black contains dithering from other colours, making it even more critical with alignments. Would prefer a setting that used only black ink, but don't know of such.
Looking through a good quality 10/20x microscope.
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Together with your target, I've put in the resolution test image from the bottom of this page, http://www.clarkvision.com/articles/printer-ppi/ (http://www.clarkvision.com/articles/printer-ppi/).
Printing on a Canon Pro-1000 at 600 dpi on a high-glossy paper, I notice I cannot separate 1 pixel bars (the tiniest) from clarkvisions test image, on vertical lines that is (running up/down, perpendicular to print head movement axis) - on horisontal lines they are easy to distinguish. Does that indicate the need for a head alignment (and not feed adjustment)?
Tried unidirectional printing, and that helps precision / edge separation of vertical lines.
Printer is almost new, and had a head alignment on the paper included for the task at initial setup, and has printet very little amounts yet. Perhaps head alignment needs to be paper / media type specific (guess it'll only have on alignment saved though, even it could make sense per media type / head gap).
Also notice that black contains dithering from other colours, making it even more critical with alignments. Would prefer a setting that used only black ink, but don't know of such.
Looking through a good quality 10/20x microscope.
Hi Henrik,
Yes, vertical lines can benefit from head alignment, because the most prominent variable is the horizontal head movement and thus horizontal spacing. However, the alignment procedure might also involve the paper feed direction, and there may be interdependencies (due to the weaving on multiple passes). In principle, besides uni-directional printing, the head speed also has an effect since droplets will strike the media surfaces literally on-the-fly and could deform them a bit.
A second check, besides the square patches with fixed resolution in 4 directions, for asymmetric resolution in my target is the central star section. If resolution is symmetrical, then there will be a more or less disc-shaped region towards the center of the star that is unresolved (ideally up to the 600PPI resolution indicator). Otherwise, it may become a more elliptical blur area.
The nextl variable is the print medium itself, but it should blur (through ink diffusion) more or less equally in all directions (besides the earlier mentioned head travel speed).
Unclear is if/how the height of the heads above the print surface is managed with media of different weight/thickness. To play safe I usually recommend to use the same media (thickness) for alignment as the media that are going to be actually used. In general (semi) glossy media should be best for alignment purposes, assuming that they show the least amount of ink-diffusion and thus show the alignment patterns more clearly.
I suggest to look closely at how the resolution is limited in the central star region (how much more than the 300 PPI circle is resolved, how close to 600 PPI can you get?). That might give a clue as to what might cause resolution asymmetry. Fixed resolution patterns may also be affected by profile non-linearity, and may cause issues that are not noticeable in regular images (which is what the radial sinusoidal star patterns try to simulate).
Cheers,
Bart
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Yes, an old thread.
If Bart is around I might be lucky. Some questions I have.
Anyone tried the printer target on the Overdrive setting of Qimage Ultimate? I know it extrapolates to 1200 PPI or 1440 PPI and the Printer settings ask not more than 600 or 720 PPI (Finest Detail) but it could improve the print according Mike of Qimage Ultimate. On a Z3200 I printed the 600 PPI target but also a shrunk 1200 PPI 65x65 mm version (so not resampled) next to it in the same print run. In the Qimage Ultimate route the 600 PPI will be upsampled to 1200 PPI, the 65x65mm target not.
From older tests with the Qimage Ultimate target I recall that when a 2x higher resolution than by the driver requested 300 PPI or 600 PPI input is used, so a 600 PPI and a 1200 PPI (shrunk again, not resampled) a downsampling to the requested PPI number happened, strong aliasing showed that had nothing to do with the 2400x1200 droplet per inch squirted resolution. Driver downsampling the cause. This was before the Qimage Ultimate Overdrive setting in the interpolation choices was available.
Now I notice more aliasing effects in the shrunk target print 4 cycles/mm patch compared to the 8 cycles/mm in the original target and on more spots. But on the other hand the "Siemens star" shows better contrast up to the RED cirkel (was 300 PPI threshold, is 600 PPI threshold in the 65x65mm version) than up to Green cirkel in the 130x130 target. On the lines not giving aliasing from the outside up to the RED cirkel, there is aliasing at several angles though, the same with the circles in the center. Counting the lines per mm shows that the lines I mention are not aliased versions half the number. It is unclear to me whether the aliasing this time is also caused by downsampling in the driver and less pronounced due to the differences between the QU print target and Bart's design. Another option is that Mike found a wormhole to get 1200 PPI to the dithering stage of the driver, bypassing downsampling. BTW in the first driver of the HP Z3100 there was a printing quality setting that asked for 1200 PPI, disappeared in later versions.
Way longer back I used to send small texts for cards at 720 PPI to the 15-17 year old Epson 9000 that did not request more than 360 PPI and the text printed sharper than by sending 360 PPI. I have to say that was text created with Acorn Risc Os applications that used sub-pixel anti-aliasing for any output, video, print, etc. Which may have coped well with a downsampling routine in the 9000 driver or the driver did not downsample.
Targets, text, are not 1:1 to photo image structures so not all is said yet about the information transfer from image to print in printing. Barts's target is probably the best for photo images we can use right now. Which brings me to another question, what would be a good set up in targets, scanning or camera copying, to measure the transfer quality of a specific printer paper system? In that system changes of papers and the measured results then. Are there elements in Bart's target usable? Another step includes the eye acuity threshold in that transfer system but this time not a single threshold but let us say what a perfect young eye at 2000 lumen as close by as possible can resolve and the usual 300 PPI at a foot viewing distance, the RED circle in Bart's target.
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
March 2017 update, 750+ inkjet media white spectral plots
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Hallo Ernst,
I'll give a reaction after at least getting some sleep tonight. I'm a bit busy but do want to get to the bottom of Qimage's Overdrive setting. Earlier attempts didn't get me better resolution than 600PPI on a Canon printer, maybe I need to try another printer and/or other media as well. In the meantime, Mike Chaney also improved the printing behavior of fine testchart detail, but he (understandably) didn't want to disclose what to look for specifically when I asked him (I suspect something to do with dithering, but I'm not 100% sure).
Cheers,
Bart
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Hallo Bart, er is geen haast,
I will make more prints with different settings after aligning the heads again on a sheet instead of a roll. Might make a difference.
Could send a set to you, well described, so there is more reference. Have to do work too till the end of the week at least.
Will check the Qimage printing targets as well then.
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
March 2017 update, 750+ inkjet media white spectral plots