Clarification on Print Resolution

[Aristoc]

so nobody really knows for certain if an Epson printer driver resamples/interpolates or whatever? 

[Mark D Segal]

I think Jeff answered that question. But you know, once we run our tests to see what approach to resolution works best for each of us and we get our answers so we know what to do, it doesn't really matter, does it? I won't find a print looking better if I knew the data was resampled in Lightroom versus the Epson driver, quite frankly. Sure, it's educational to understand more about how these processes work, but there's so much beyond this one item we'll never know anyhow...........huh?

[Ernst Dinkla]

so nobody really knows for certain if an Epson printer driver resamples/interpolates or whatever? 

To get that knowledge use hard edge B&W resolution targets with a 1440-720-360 LPI pattern (lines preferably) and print that with different printer quality settings that ask for 720-360-180 PPI input. It is easy to tell whether the driver downsamples first and then dithers or does the dithering right away. In the last case you can expect a more or less averaging to grey in total, in the first case it will stay B&W but lines disappear and/or complete black blocks appear, kind of moiré. I have done that some years back with 1200-600 LPI line targets to the HP Z3100 driver asking for 600 or 300 PPI input, to check whether the driver at least does anti-aliasing in its downsampling. It did not. That is also the flaw in this test, if the driver applies an anti-aliasing routine in downsampling then the print may not be that different from a right away dithered print, both more or less grey. For the Epson 9900 I expect that you will see B&W moiré but I do not have one here to test it.

If it is verified for downsampling to the native resolutions then I expect it to do the same in upsampling to the native resolutions. But I have no test for that.


met vriendelijke groeten, Ernst

Dinkla Gallery Canvas Wrap Actions for Photoshop

http://www.pigment-print.com/dinklacanvaswraps/index.html

[Farmer]

While true, I assume there is also an even simpler underlying reason. When the PPI results in a value above 300/360 for the output size chosen, at the default settings the printer driver will resample (yes, I do believe resampling takes place) down to 300/360 PPI. Sub-optimal interpolation/resampling is one thing, but improper (if any) AA-filtering before downsampling the pixel data can look terrible. I'm not suggesting that the Epson person was lying to you, but maybe he also didn't tell the whole story ...

Anyone here who knows more than is already in the public domain, can't say anything more than they've already said. It's a big leap to suggest that Jeff was mislead or not given the whole story in order to support your assumption.  He's giving you information received directly from the source.  Do with it as you like :-)

[Bart_van_der_Wolf]

Do with it as you like :-)

I fully agree, and I do. However, when confronted with the following example, actual print enlargements from original Sigma SD14 1:1 crops, both with identical printer driver settings (first crop is from LR3, second crop is from Qimage):


I can only wonder why people question the benefit of better quality resampling versus letting the printer driver do it's thing.

Cheers,
Bart

P.S. The images were directly linked from a message from Mike Chaney. I hesitate to link to it directly because there seems to exist a somewhat allergic reaction with some forum dwellers when Qimage is mentioned, where I only want to underline the importance of better quality resampling, regardless of the method used.

[Farmer]

I don't think anyone's suggesting that if you resample, you shouldn't do the best that you can.  Without knowing the exact details of each workflow it's hard to compare or to say whether the best of each was being used.  Furthermore, it doesn't show one way or the other whether a particular driver does or doesn't resample.

[Ernst Dinkla]

Furthermore, it doesn't show one way or the other whether a particular driver does or doesn't resample.

No, but I gave a route to test whether resampling in the driver is done or not when there is too much input resolution.

The resampling Bart shows looks nice to me, is it the new fusion algorithm or the older hybrid version of Qimage?


met vriendelijke groeten, Ernst

New: Spectral plots of +250 inkjet papers:

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

[Bart_van_der_Wolf]

No, but I gave a route to test whether resampling in the driver is done or not when there is too much input resolution.

The resampling Bart shows looks nice to me, is it the new fusion algorithm or the older hybrid version of Qimage?

I'm not sure, Mike didn't mention, but it was an addition to his March 2010: Smart Photo Printing article on his Tech Support forum. I believe the new Fusion algorithm is of more recent date, so I'll have to give that a try some day as well. Hybrid SE is pretty good, because it produces no halo and thus is a good basis for either Smart sharpening or e.g. Deconvolution sharpening on a print file (if the size is still manageable). For large output QI seems to handle the memory for large files better than an average printdriver.

Having said that, I try to let this thread not turn into an application X versus Y pissing contest. Just some considerations about what is needed to get the best output, and what to avoid (or do) with printer driver settings, with examples to illustrate.
 
Cheers,
Bart

[Ernst Dinkla]

Having said that, I try to let this thread not turn into an application X versus Y pissing contest. Just some considerations about what is needed to get the best output, and what to avoid (or do) with printer driver settings, with examples to illustrate.
 
Cheers,
Bart

That is not my intention either but I am more familiar with Qimage and it would surprise me if a printer driver adapts itself to the application that calls it. So for samples., explanations and tests on what does the resampling I will refer to that application. Of course I could be wrong and what Jeff writes only applies to LR running on a Mac to drive an Epson.

met vriendelijke groeten, Ernst
New: Spectral plots of +250 inkjet papers:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

[Schewe]

I'm not sure, Mike didn't mention, but it was an addition to his March 2010: Smart Photo Printing article on his Tech Support forum.

Well, if you don't know exactly how each of the examples were made, the samples' usefulness drops considerably...so, was the LR 3 sample upsampled to 720 in LR3 and output sharpened? Without basic information, it really doesn't bring much to the discussion.

[Ernst Dinkla]

To get that knowledge use hard edge B&W resolution targets with a 1440-720-360 LPI pattern (lines preferably) and print that with different printer quality settings that ask for 720-360-180 PPI input. It is easy to tell whether the driver downsamples first and then dithers or does the dithering right away. In the last case you can expect a more or less averaging to grey in total, in the first case it will stay B&W but lines disappear and/or complete black blocks appear, kind of moiré. I have done that some years back with 1200-600 LPI line targets to the HP Z3100 driver asking for 600 or 300 PPI input, to check whether the driver at least does anti-aliasing in its downsampling. It did not. That is also the flaw in this test, if the driver applies an anti-aliasing routine in downsampling then the print may not be that different from a right away dithered print, both more or less grey. For the Epson 9900 I expect that you will see B&W moiré but I do not have one here to test it.

If it is verified for downsampling to the native resolutions then I expect it to do the same in upsampling to the native resolutions. But I have no test for that.

To make it easier, here is the Epson target to use so you can deliver evidence for Jeff's statement:

http://www.ddisoftware.com/qimage/quality/restest-epson.zip

more info on how to use them for normal testing

http://www.ddisoftware.com/qimage/quality/

In this case you should not just use the highest printer quality setting but also the lower quality settings as described above. For 1440 PPI input resolution, print the target image at 50% of its size.

met vriendelijke groeten, Ernst

Try: http://groups.yahoo.com/group/Wide_Inkjet_Printers/

[Farmer]

All of which is interesting, Ernst, but doesn't address the issues raised by Jeff, myself and others - without precise knowledge of the two workflows it is not useful to make a comparison.

Following your suggestion of testing is a much better idea than relying on the samples provided here, imho, because it allows a user to know what they are comparing and to use the optimal workflow in each case.

[rwheat]

My experience shows that sending my Epson 3800 anything less than 360ppi risks degraded output.  In contrast, the figure is 240ppi with my HP Z3100.

HTH.

[Ernst Dinkla]

All of which is interesting, Ernst, but doesn't address the issues raised by Jeff, myself and others - without precise knowledge of the two workflows it is not useful to make a comparison.

Following your suggestion of testing is a much better idea than relying on the samples provided here, imho, because it allows a user to know what they are comparing and to use the optimal workflow in each case.

The test with line targets with a resolution exactly twice the printer input resolution (as set by printer driver quality choices) reveals whether the driver does downsampling to that input resolution or starts dithering right away. To me that aims at the essence of this debate. It is a simple task for the owner of a recent model Epson. Use Photoshop or another application that will not interfere with resampling by itself.

met vriendelijke groeten, Ernst

New: Spectral plots of +250 inkjet papers:

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

[Bart_van_der_Wolf]

The test with line targets with a resolution exactly twice the printer input resolution (as set by printer driver quality choices) reveals whether the driver does downsampling to that input resolution or starts dithering right away. To me that aims at the essence of this debate. It is a simple task for the owner of a recent model Epson. Use Photoshop or another application that will not interfere with resampling by itself.

Indeed. If printing that file at any PPI other than the native printer resolution produces aliasing , then resampling is what caused it. Downsamping by the printer driver (native resolution set too low) will be most likely be worse than upsampling. Only the remote posibility of some strange software bug could keep the conclusion from being 100% certain. Stochastic dithering doesn't cause aliasing, and even simple dithering won't (it might cause a visble dither pattern, but no aliasing).

In fact, in some cases the resampling by the printer driver is so mediocre, that any resulting PPI other than the native one (for the driver settings) will cause artifacts on the critical test targets mentioned in this thread (like in the 359/360/361 test case). The artifacts do not necessarily show as prominent on normal images, but that doesn't mean there is no resampling.

Cheers,
Bart

[Ernst Dinkla]

My experience shows that sending my Epson 3800 anything less than 360ppi risks degraded output.  In contrast, the figure is 240ppi with my HP Z3100.

HTH.

I do not think that the discussion is about which printer delivers best output etc but nevertheless:

With a variety of 4 and 6 picoliter droplets the Z3100 will not make an optical resolution as high as the Epson 3800 which can rely on 3.5 picoliter droplets for best quality.  There is a rough rule to compare:  3.5 : 5 picoliter = 0.7 0.7 x 360 = 252 close enough to your 240. The HP will not ask for 360 PPI input but for 300 PPI which makes it all quite logical. Given good + enough data and maximum paper coating quality the higher input qualities of 600 or 720 PPI are available for resp the HP and Epson so the HP print quality is not limited to the 240 PPI you quote for 300 PPI input. A similar approach for a Canon iPF model, 4 picoliter throughout (in all dpi resolutions), this time not for input resolution but for for dot resolution: 3.5 : 4 = 0.875  0.875 x 1440 dpi = 1260, close enough to the 1200 dpi of the Canon. 0.875 x 2880 dpi = 2520, close enough to the 2400 dpi of the Canon. Whether the droplet size and/or dot placement are defined exactly by the numbers published is another question. A rough rule it is, the HP B9180 has to work with the same 4-6 droplet heads the Z3100 has but its dithering/weaving algorithms are better (and will take more processing time per square foot), so lays down a better print quality despite the same droplet sizes. With the exception of the B9180 all manufacturers use smaller droplet sizes, 2- 1 picoliter, for photo quality A3 and A4 printers as the expected viewing distance for print sizes like that will be less.


met vriendelijke groeten, Ernst

New: Spectral plots of +250 inkjet papers:

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

[rwheat]

I do not think that the discussion is about which printer delivers best output etc but nevertheless:

With a variety of 4 and 6 picoliter droplets the Z3100 will not make an optical resolution as high as the Epson 3800 which can rely on 3.5 picoliter droplets for best quality.  There is a rough rule to compare:  3.5 : 5 picoliter = 0.7 0.7 x 360 = 252 close enough to your 240. The HP will not ask for 360 PPI input but for 300 PPI which makes it all quite logical. Given good + enough data and maximum paper coating quality the higher input qualities of 600 or 720 PPI are available for resp the HP and Epson so the HP print quality is not limited to the 240 PPI you quote for 300 PPI input. A similar approach for a Canon iPF model, 4 picoliter throughout (in all dpi resolutions), this time not for input resolution but for for dot resolution: 3.5 : 4 = 0.875  0.875 x 1440 dpi = 1260, close enough to the 1200 dpi of the Canon. 0.875 x 2880 dpi = 2520, close enough to the 2400 dpi of the Canon. Whether the droplet size and/or dot placement are defined exactly by the numbers published is another question. A rough rule it is, the HP B9180 has to work with the same 4-6 droplet heads the Z3100 has but its dithering/weaving algorithms are better (and will take more processing time per square foot), so lays down a better print quality despite the same droplet sizes. With the exception of the B9180 all manufacturers use smaller droplet sizes, 2- 1 picoliter, for photo quality A3 and A4 printers as the expected viewing distance for print sizes like that will be less.

Hmmm... thanks Ernst for the information, you have given me something to think about (I've read it through three times and almost understood it).

I did not intend to comment on which printer produces best output, however I can see why you took my comment that way.

My intention was to comment on the marked difference in print quality produced when using the same ppi value on different printers. E.g. from the same source file and using my personal standard of print quality, I can produce a larger print using the HP, than I can with the Epson.  I.e. when I am printing a BW image with fine diagonal lines, I have to up the source size and send it to the Epson at 360dpi to avoid jaggies which are not present in the HP's output at 240ppi.  I am not commenting on the highest print quality that can actually be achieved by either printer.

Up until now I had thought that the HP (along with the driver etc.) merely had a better interpolation algorithm than the Epson.

Am I reading you right in saying that this is actually a result of the Epson having an overall higher resolution?

Thanks,
Richard.

[Ernst Dinkla]

Up until now I had thought that the HP (along with the driver etc.) merely had a better interpolation algorithm than the Epson.

Am I reading you right in saying that this is actually a result of the Epson having an overall higher resolution?

Thanks,
Richard.

Richard,

Both are possible. In theory the Epson should be able to achieve better print resolution given the same extrapolation algorithm before printing is used. But from which application did you print?


met vriendelijke groeten, Ernst

New: Spectral plots of +250 inkjet papers:

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

[rwheat]

Both are possible. In theory the Epson should be able to achieve better print resolution given the same extrapolation algorithm before printing is used. But from which application did you print?

I print from both QImage and Photoshop, under Windows Vista 64bit.  I never let QImage resize the images.  Both applications produce the same results.

Thanks,
Richard.

[John R Smith]

I've removed this post because I realised that the question I was asking was actually a non-question. Further thinking has caused light to be shed on the purpose of Ernst's test image, so I will have to go back to the beginning and run my trials again. A new (and hopefully more coherent) post will follow.

John