Luminous Landscape Forum
Equipment & Techniques => Cameras, Lenses and Shooting gear => Topic started by: Dan Wells on December 11, 2015, 06:50:41 pm
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I teach photography, and get a ton of gear questions. One that's always bugged me is "does a high-resolution body matter with any but the best lenses". i just ran across a fascinating test on Bob Atkins' website, which shows that body resolution DOES matter even with the worst lenses (I honestly had no idea how this one would come out until I read the article). The test is within his review of the Canon 5Ds, which is here:
http://www.bobatkins.com/photography/digital/canon_eos_5Ds_review.html
He first does what we're used to seeing - uses a world-class lens (Canon's 85 f1.2 L) at its best aperture (f4) and shows us the high-resolution 5Ds image as a 100% crop and the lower resolution 6D image, upscaled to the same size. NO Contest (nor would you expect one - if the 85 f1.2 at f4 couldn't take advantage of the resolution, what could)?
His second test is the one that I hadn't seen before - he went hunting for the WORST lens in his collection, and he did pretty well - how many of us own a piece of "glass" (a lot of this beauty may be plastic) worse than a Canon 22-55 kit lens from their APS film IX Lite camera? It seems to have been about a $100 lens even sold separately, probably $50 with a body, and it's a 15 year old plastic-mount special designed for a format smaller than the FF cameras he was using it on... Pretty satisfactory definition of a lousy lens? I honestly can't think of how to do worse without resorting to a DELIBERATELY distorting lens (a lensbaby, or a Holga lens somehow attached to a DSLR, or a pinhole)?
The two images show nearly as much difference as the two captured with the great lens. No, the sharp image is not as sharp, but the degree of improvement is NOT that different. I'm assuming his test conditions were decent, although he doesn't go into any detail, he's been around the Canon world a long time, and is well respected.
I've attached Bob's images below - I hope he doesn't mind the publicity for his interesting test. I can actually see the differences in the thumbnails on here easily enough.
No, this doesn't mean "all lenses outresolve all cameras", but, rather that low resolution is additive - even a less sharp lens will be improved by a sharper sensor.
Within the realm of "reasonable" combinations (nobody is actually going to use that 22-55 on a 5Ds, or a 1980s Nikon FM10 kit lens on a D810, except as a test), it seems like both body and lens matter. The high-pixel bodies will perform their best with fancy lenses, but they'll give any lens a boost.
I suspect that, unlike cellphone dynamic range showing up in tiny images (I can tell a phone picture from a great distance, due to blown highlights and blocked shadows), the resolution effects will still require decent scale. I wonder what that scale is - can our eyes perceive detail we aren't quite conscious of? Some photo connoisseurs claim to be able to tell the difference between an 8x10 contact print and an 8x10 enlarged from a 4x5 original. That's supposedly beyond the range of human vision (even enlarged 2x, film grain should still be comfortably microscopic). Are they seeing things, or is it the "pipe organ phenomenon"? A large pipe organ can play notes well below the range of human hearing, but you can tell that those notes are sounding. Similarly, sounds ABOVE the range of hearing have been shown to subtly affect our perception of music. Is detail in a photograph similar?
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Hopefully, someone here will recall the formula for calculating system resolution from the resolution of the individual components. I do know it shows exactly what Bob describes.
(FWIW, Bob doesn't seem to have anything about himself on his site, but I we once worked at the same company so I know he was a Member of the Technical Staff with a PhD. He's not some guy on the internet.
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Aren't there a LOT of ways to "scale" an image? Aren't some methods better than others? Scaling to compare images always seems like a weak point in these kinds of analysis to me.
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I agree, I think it depends on your usage as to what scaling method and what comparison is appropriate. Perceptual sharpness is a slippery mix of actual sharpness, micro contrast, purity of blacks and whites (a subtle flare can manifest as lack of sharpness rather than lack of contrast if you're not looking for it), etc. etc..
If you are producing huge prints, the method in the article is surely the right comparison to make.
If you're downsampling everything for the web, a more appropriate test would be to down-sample both cameras to some common smaller size using a sensible rescaling algorithm (which is what DxO do in some of their comparisons I believe).
My own highly unscientific experience bears out the conclusions of the article, even though a lot of my work ends up viewed at web size. I've been using the same physical trio of cheap-ish Canon prime 35, 50 and 85 mm lenses on my Canons since my first D30 and the oversampling clearly had huge benefits going from that through 5D Mark I and 5D Mark II. So I'm not surprised to see the benefits carry on to even higher oversampling, even with crappy lenses.
The A7R II photos with these same lenses are better again... but not as good as with brand new Sony 55mm and 28mm lenses. So lens and sensor resolution both play a part. Presumably it is a game of diminishing returns eventually.
Cheers, Hywel
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Completely agreed that it depens on what you're using it for - some amount of oversampling matters relative to final output pixels, but Bob Atkins' test doesn't resolve how much. His question was whether, if 50MP was the ultimate desired resolution , there was any difference between a real 50 MP camera and an upsampled ~20 mp camera, both with good lenses and with lousy lenses? This seems pretty conclusive that you DO get a better 50 MP file by photographing one in the first place, rather than upsampling, regardless of lens. If your goal is, say, a 2 MP file for web use, oversampling with an 8 MP camera is clearly better than using a 2 MP camera (the oversampling reduces noise), but is massively oversampling with a 50 mp camera better than oversampling with a 20 mp camera? I don't know, and this test doesn't answer that question. My working hypothesis would be that, all else being equal (and a phone camera is NOT equal - I can spot their restricted dynamic range across a room, even in a tiny image), there is some fairly low limit to how much oversampling makes sense - nothing over 16 MP probably matters for even the highest resolution non-printed display, if that.
For printing, however, 50 MP is 240 ppi at 24x36", so it DOES make sense for large prints - just for kicks, modern Canon and Epson printers work internally with ~600 dpi, so an astonishing 310 mp is where you "run out of printer"for a 24x36" print. Could any human tell a true 310 MP 24x36" print from a 50 MP print (which is at the resolution of a Retina display)? If yes, what about a 100 MP print that is over 300 DPI? Ansel Adams and some friends once tried to work out what our visual acuity actually supported based on viewing distance, and it doesn't suggest huge resolutions (but they continued right on making 8x10" contact prints, which probably work out to something alarming well over 1200 ppi).
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I don't currently own any lousy lenses, though the sharpness über alles folks might argue with my definition of "lousy". I do notice that the Sony A7r2 records the character of various lenses just as all my other electronic cameras do (and in the past have done). The higher res is just higher res, not some magical phase transformation to a new realm of image making. :)
-Dave-
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Hi,
I guess that the best way to describe it is to see thing like deterioration of information. Image is transferred over a chain of information carriers. Lens, sensor, postprocessing, display and human vision.
At each stage some information is lost and some disinformation is added. So each stage transfers a percentage of information, that is what we call MTF, and adds some disinformation what we call artefacts, aberrations or just noise.
The MTF part multiplies. So, lens perhaps transfers 60% and sensor transfers 60%, so total transmission would be 0.6 *0.6 = 0.36 that is 36 percent.
So improving sensor will improve information transfer. A better sensor may transfer 80% of the information, so with the very same lens we may transfer 0.6 * 0.8 = 0.48.
This essentially means that a significant improvement to any part of the imaging chain will improve the fidelity of the whole imaging chain. So the imaging chain is not dominated by it's weakest link, but is best described as a product of the quality of it's components.
Best regards
Erik
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Sometimes I stitch two or three frames together with the canon 24mm tilt shift lens, thinking I'll gain resolution by the stitch. But the quality of it is so bad that I'd probably be better off just shooting it straight with a sigma Art lens, in one frame. Maybe it's just my copy of the 24. I don't know. But when at 100% in Photoshop, a bad lens is instantly obvious. Save all the time and trouble of stitching, by just shooting it with a good zeiss or good sigma.
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... But the quality of it is so bad...
I'd love to see that.
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I think part of the problem is that TS lenses are manual focus. I think with digital, it requires Autofocus, or Live View approach. There is very little tolerance for mistake in manual focus. Maybe architectural guys would use it with Live View, but for me, way too slow.
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I teach photography, and get a ton of gear questions. One that's always bugged me is "does a high-resolution body matter with any but the best lenses". i just ran across a fascinating test on Bob Atkins' website, which shows that body resolution DOES matter even with the worst lenses
Of course it does. The throughput quality factor (?) is not the lesser quality component bottleneck, but the product of the quality factors or each component. Quality factor is 1 for a perfect component and 0 (zero) for a totally nonworking one.
Mediocre camera with bad lens: 0.6 x 0.2 = 0.12
Great camera with the same bad lens: 0.9 x 0.2 = 0.18
Simple as that.
With this method it is possible to estimate where to put the money when improving the throughput quality of a system: to the component where the component quality improvement is the biggest per dollar invested. For hi-fi systems this is quite clear; electronic components are practically perfect compared to even the best speakers. For cameras more sensor resolution is often better investment than marginally better lens which costs 4 times as much as a good one.
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Of course it does. The throughput quality factor (?) is not the lesser quality component bottleneck, but the product of the quality factors or each component. Quality factor is 1 for a perfect component and 0 (zero) for a totally nonworking one.
Mediocre camera with bad lens: 0.6 x 0.2 = 0.12
Great camera with the same bad lens: 0.9 x 0.2 = 0.18
Simple as that.
It is not that simple in practice. MTFs do multiply, but one must convert from the spatial domain to a frequency domain by first performing a Fourier transform, multiply the MTFs, and then convert back to the spatial domain as explained by Norman Koren here (http://www.normankoren.com/Tutorials/MTF.html) (scroll down to the Imaging Systems section). Not being an expert in these matters, I don't how one would do this in practice.
Bill
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Of course resizing something from 20 Mpx to 50 Mpx is generally going to look like crap. Downsizing 50 Mpx to 20 Mpx, however, might seem like a better idea. After all, bigger sensors show their advantage when printed big, no doubt.
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It is not that simple in practice.
My example was not exact science, just the general principle.
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And you have to remember that noise behaves differently, too. You can never truly remove noise from the data once it is added; later stages of amplification and processing can at best amplify the noise already there along with the signal, and probably add some noise of their own.
From this point of view it is necessary to do the best job you can on the earliest stages of processing, because noise added there is there forever. That's why low noise preamps are so critical for sound recording (and data recording for scientific data in general).
There is a sense in which this is relevant to lenses and cameras, too. We don't normally think of a lens introducing noise, but it does if you consider that the desired "signal" is the photons at the sensor which come from the "correct" light path. MTF might go multiplicatively through the chain, but "noise" in this sense of light contamination from flare and internal reflections (and even in some sense physical effects like diffraction and aberrations) screws your signal up at source. Once it is there you can't get rid of it, your signal is degraded forever, and other parts of the processing chain are stuck with this noise.
Some stuff you might be able to deconvolve with sophisticated image processing (see Hubble telescope pre-fix, or the way that modern cameras correct for some aberration and distortion, even sometimes in the raw files) So it's not 100% accurate to characterise this in the same way as truly random sources of noise which are truly not separable from the signal. In any case it'll never be as good as getting a clean signal in the first place- see Hubble telescope post-fix.
But it is useful to realise that not everything in the imaging chain is as simple as it might look and that the naive "these sensors are out-resolving the lenses so higher resolution doesn't help" calculations don't hold up to actual measurements. Tests are the only way to really know for your own use case.
Cheers, Hywel
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Hi,
Our computer screens used to be around 2MP. So 12, 24 or 50 MP is not visible on computer screen without pixel peeping.
Making prints, it is a different thing.
Epson printers have normally 360 PPI internal resolution which is a good match for what is considered normal human vision at 25 cm / 12" viewing distance.
So, having a 24 MP camera we could print something like 28x42 cm (11x16") using the 360 PPI resolution. Anything larger, and it will be downsized anything smaller and it will be upsized.
With 42 MP, you could print 37x55 cm (14x22") at 360 PPI, that is a bit smaller than European A2.
So, to properly pixel peep, for A3 size print the images should be downsized to around 24 MP. While for A2 the images would be needed to upsized to something like 54 MP.
Now, an upscaled image will look ugly on screen as actual pixels on screen corresponds to a large magnification. But, that is exactly what is gong to sent to the printer.
In practical experience, it seems that 180PPI is quite enough for a good print. The reason is that our vision is not dominated by resolution but by contrast at lower frequencies. So good post processing makes it possible to achieve very good print quality from smaller formats, although they may lack ultimate detail.
An example of that was that I made some A2 (16 x 23") prints for an exhibition, one of those was from a 12 MP camera, 12 MP with good light beats 24 MP with boring light any day. That print looked really good, except it had a lot of dust spots. Looking at the image, I realised that those dust specks were birds. With 50 MP the print perhaps would show enough details to see that those were birds.
Structures, like mountain sides, still looked good in that A2 size print. As a general comment, when I have gone from 12 MP APS-C to 24 MP full frame I have shot some comparison images and printed at A2, at least in one case I couldn't tell the images apart, but in general the 24 MP images were a bit better. But the difference was far less than on screen. Going from 24 MP full frame to 39 MP on MFD I really found that I could not observe difference between 24MP and 39MP with the naked eye in A2-size prints. The difference was obvious when viewing the image with a loupe.
Best regards
Erik
(http://echophoto.dnsalias.net/ekr/Articles/Exhibitions/BergDalOchVatten_1/20080928-DSC00956.jpg)
Of course resizing something from 20 Mpx to 50 Mpx is generally going to look like crap. Downsizing 50 Mpx to 20 Mpx, however, might seem like a better idea. After all, bigger sensors show their advantage when printed big, no doubt.
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No, this doesn't mean "all lenses outresolve all cameras", but, rather that low resolution is additive - even a less sharp lens will be improved by a sharper sensor.
It is generally all additive from the lens out front to the output medium and including technique and lighting conditions.
Looking at it from the pessimistic view point, there is a perfect image out there and all our technology and technique does is degrade it. Of course, what we are striving for is the minimum amount of degradation throughout the chain!
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Making prints, it is a different thing.
Epson printers have normally 360 PPI internal resolution which is a good match for what is considered normal human vision at 25 cm / 12" viewing distance.
So, having a 24 MP camera we could print something like 28x42 cm (11x16") using the 360 PPI resolution. Anything larger, and it will be downsized anything smaller and it will be upsized.
Hi Erik,
Yes, 300 - 360 PPI is a good match for human visual acuity at normal reading distances, at good illumination levels. However, the printer is actually printing at 600 PPI or 720 PPI, unless we reduce that to 300 PPI or 360 PPI by not selecting the proper settings. This may seem overkill, if we cant see it why would we do it, one could ask? Well, there can be subject matter that is resolvable by eye and that exceeds the average 20/20 vision acuity, calling on the Vernier resolution capability of our vision, AND with more (smaller) pixels to print we can use better output sharpening.
While I agree that, also due to larger viewing distance, we can print with quite a nice image quality at the lower PPI choices, there is a distinct benefit to using the higher resolution settings, even if that means we need to upsample the output before sending it to the printer. When one uses high quality upsampling software, e.g. PhotoZoom Pro, one can even increase resolution of edge detail beyond what the camera sensor has to offer.
There is also a chance that, on certain subject matter, what looks like aliasing is just bordering on aliasing but due to interference the detail looks crude/rough/pixelated, but once upsampled it looks correct because it was not really aliased.
In practical experience, it seems that 180PPI is quite enough for a good print. The reason is that our vision is not dominated by resolution but by contrast at lower frequencies. So good post processing makes it possible to achieve very good print quality from smaller formats, although they may lack ultimate detail.
In principle yes but, given the choice, who could object to better image quality also when viewed from shorter distances. The viewing experience becomes a lot more immersive, and material structure is much better depicted with more than barely adequate resolution.
And as to the OP's question, improving sensor resolution will always improve the captured lens quality, because denser sampling of the projected lens image will boost the overal MTF and increase limiting resolution. As others have said, component MTFs multiply to achieve an overall system MTF, and it's the worst contributing component that sets the achievable ceiling. Sensors are usually worse at resolving detail than decent lenses, so usually most gain is to be had by increasing sensor resolution (which also opens opportunities for signal restoration with dedicated software).
Cheers,
Bart
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Just what I need - more G.A.S. !
Atkins' result is really not too surprising. (Neither is the G.A.S. :-\ )
I am still wondering about the TS-E 24 v. II, a long-time subject of my personal G.A.S, not yet tried by me. Wouldn't most people use Live View with such a lens? And even with Live view, they have problems with sharpness? Is it just a matter of not quite getting the tilt right? Or is it expecting too much out of the tilt, since anything out of the exact plane of critical sharpness is going to be "less sharp"?
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Trying to make a direct comparison of a dithering printer to a continuous tone device is a fools errand. There is a 1-1 correspondence between image pixels and printed output with each pixel being any one of the total number of colors the continuous tone output medium has to offer.
Epson (all inkjets) have a limited color set. The hardware has the ability to place a certain number of drops per linear inch in each dimension of a specific size and specific color. This is where the 360, 720, 1440 and 2880 numbers come from. But there is no direct correspondence between a droplet and a pixel. The apparent resolution of the image is significantly impacted by the substrate on which the ink is placed (how much ink can be laid down and how much spread of the drop occurs).
I have owned just about every Seiko Epson Stylus Photo desktop printer ever made. I also worked on a government program with Epson.
Some Points directly:
1. Epson printers do not resample the image prior to passing through the dithering algorithm
2. The minimum resolution that should be sent to the printer reasonable quality output is 180ppi
3. The algorithm performance tends to top out at around 300-360ppi, except for images with specific characteristics (Epson declined to identify these characteristics) when higher pixel densities might yield marginal increases in apparent quality.
4. Only up sample an image if the up sampling provides a benefit to the image itself. It is not beneficial to up sample an image merely to provide the dithering algorithm with more data.
5. Long time Epson users will verify that sending multiples of 60ppi is best and that, in general, 360ppi is a good standard. Some will say that 720ppi is also reasonable. What I will say is stay away from resolutions not quite a multiple of 60ppi. For example, don't use 359ppi! Better to be 330ppi than 355ppi for example. This is because of how the algorithm itself handles the data prior to the dithering.
Hi,
Our computer screens used to be around 2MP. So 12, 24 or 50 MP is not visible on computer screen without pixel peeping.
Making prints, it is a different thing.
Epson printers have normally 360 PPI internal resolution which is a good match for what is considered normal human vision at 25 cm / 12" viewing distance.
So, having a 24 MP camera we could print something like 28x42 cm (11x16") using the 360 PPI resolution. Anything larger, and it will be downsized anything smaller and it will be upsized.
With 42 MP, you could print 37x55 cm (14x22") at 360 PPI, that is a bit smaller than European A2.
So, to properly pixel peep, for A3 size print the images should be downsized to around 24 MP. While for A2 the images would be needed to upsized to something like 54 MP.
Now, an upscaled image will look ugly on screen as actual pixels on screen corresponds to a large magnification. But, that is exactly what is gong to sent to the printer.
In practical experience, it seems that 180PPI is quite enough for a good print. The reason is that our vision is not dominated by resolution but by contrast at lower frequencies. So good post processing makes it possible to achieve very good print quality from smaller formats, although they may lack ultimate detail.
An example of that was that I made some A2 (16 x 23") prints for an exhibition, one of those was from a 12 MP camera, 12 MP with good light beats 24 MP with boring light any day. That print looked really good, except it had a lot of dust spots. Looking at the image, I realised that those dust specks were birds. With 50 MP the print perhaps would show enough details to see that those were birds.
Structures, like mountain sides, still looked good in that A2 size print. As a general comment, when I have gone from 12 MP APS-C to 24 MP full frame I have shot some comparison images and printed at A2, at least in one case I couldn't tell the images apart, but in general the 24 MP images were a bit better. But the difference was far less than on screen. Going from 24 MP full frame to 39 MP on MFD I really found that I could not observe difference between 24MP and 39MP with the naked eye in A2-size prints. The difference was obvious when viewing the image with a loupe.
Best regards
Erik
(http://echophoto.dnsalias.net/ekr/Articles/Exhibitions/BergDalOchVatten_1/20080928-DSC00956.jpg)
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Hi,
Jeff Schewe says that native resolution of Epson printers is 360 PPI or 720 PPI. He also says that the images are always resampled to 360 PPI or 720 PPI in the printer driver.
As Jeff used to work with Epson evaluating new technologies I assume that he has good info on the subject.
Best regards
Erik
Trying to make a direct comparison of a dithering printer to a continuous tone device is a fools errand. There is a 1-1 correspondence between image pixels and printed output with each pixel being any one of the total number of colors the continuous tone output medium has to offer.
Epson (all inkjets) have a limited color set. The hardware has the ability to place a certain number of drops per linear inch in each dimension of a specific size and specific color. This is where the 360, 720, 1440 and 2880 numbers come from. But there is no direct correspondence between a droplet and a pixel. The apparent resolution of the image is significantly impacted by the substrate on which the ink is placed (how much ink can be laid down and how much spread of the drop occurs).
I have owned just about every Seiko Epson Stylus Photo desktop printer ever made. I also worked on a government program with Epson.
Some Points directly:
1. Epson printers do not resample the image prior to passing through the dithering algorithm
2. The minimum resolution that should be sent to the printer reasonable quality output is 180ppi
3. The algorithm performance tends to top out at around 300-360ppi, except for images with specific characteristics (Epson declined to identify these characteristics) when higher pixel densities might yield marginal increases in apparent quality.
4. Only up sample an image if the up sampling provides a benefit to the image itself. It is not beneficial to up sample an image merely to provide the dithering algorithm with more data.
5. Long time Epson users will verify that sending multiples of 60ppi is best and that, in general, 360ppi is a good standard. Some will say that 720ppi is also reasonable. What I will say is stay away from resolutions not quite a multiple of 60ppi. For example, don't use 359ppi! Better to be 330ppi than 355ppi for example. This is because of how the algorithm itself handles the data prior to the dithering.
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Hi Bart,
Thanks for chiming in. My posting was essentially intended to shed some light on valid comparisons between image sizes. Should we size up or down. I agree with the points you make mostly.
Just to make a small point, the 360 PPI corresponds to one minute of arc at 25 cm, which is often regarded the resolution limit of human vision, simply because human vision cannot normally focus closer than 25 cm. But, all men and women are not created equal. I should know as I am near sighted.
I sort of bumped into this. I was complaining about staircase/zipper artefacts produced by a certain combination of sensor, lens and raw converter. An experienced printer pointed out to me that he could observe these artefacts with a loupe but not with naked eye in a large print (like 100x150 cm). I repeated the experiment and found that I could actually see the artefacts in good light, without corrective lenses. Keep in mind I am near sighted. With corrective glasses I couldn't observe them. Of course neither progressive glasses or reading glasses are made for 25 cm. But yes, young people with perfect vision may observe things not visible to older people.
The point on vernier acuity is very interesting, of course. I would also agree that higher resolution helps with post processing workflow.
For me, the most important advantage of high resolution is that it is helpful in suppressing aliasing artefacts, but I don't really feel that the 36-50 MP we have on DSLRs is sufficient to fully suppress aliasing.
Best regards
Erik
Hi Erik,
Yes, 300 - 360 PPI is a good match for human visual acuity at normal reading distances, at good illumination levels. However, the printer is actually printing at 600 PPI or 720 PPI, unless we reduce that to 300 PPI or 360 PPI by not selecting the proper settings. This may seem overkill, if we cant see it why would we do it, one could ask? Well, there can be subject matter that is resolvable by eye and that exceeds the average 20/20 vision acuity, calling on the Vernier resolution capability of our vision, AND with more (smaller) pixels to print we can use better output sharpening.
While I agree that, also due to larger viewing distance, we can print with quite a nice image quality at the lower PPI choices, there is a distinct benefit to using the higher resolution settings, even if that means we need to upsample the output before sending it to the printer. When one uses high quality upsampling software, e.g. PhotoZoom Pro, one can even increase resolution of edge detail beyond what the camera sensor has to offer.
There is also a chance that, on certain subject matter, what looks like aliasing is just bordering on aliasing but due to interference the detail looks crude/rough/pixelated, but once upsampled it looks correct because it was not really aliased.
In principle yes but, given the choice, who could object to better image quality also when viewed from shorter distances. The viewing experience becomes a lot more immersive, and material structure is much better depicted with more than barely adequate resolution.
And as to the OP's question, improving sensor resolution will always improve the captured lens quality, because denser sampling of the projected lens image will boost the overal MTF and increase limiting resolution. As others have said, component MTFs multiply to achieve an overall system MTF, and it's the worst contributing component that sets the achievable ceiling. Sensors are usually worse at resolving detail than decent lenses, so usually most gain is to be had by increasing sensor resolution (which also opens opportunities for signal restoration with dedicated software).
Cheers,
Bart
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Hi,
Jeff Schewe says that native resolution of Epson printers is 360 PPI or 720 PPI. He also says that the images are always resampled to 360 PPI or 720 PPI in the printer driver.
As Jeff used to work with Epson evaluating new technologies I assume that he has good info on the subject.
Best regards
Erik
And you would be wrong. Jeff has tremendous empirical experience with Epson output, and following his tips will lead to great images, but he still believes that the image is resampled. He has finally accepted Epson's assertion that the driver doesn't do it, but now believes that the Operating System does it. While if you have a developers kit installed it is fairly easy to trace the data and prove otherwise, at least on the Windows Platform.
A dithering printer doesn't have a "Native" resolution. Epson printers have various increments of linear distance that it can put down a drop. But it will never put down a constant number of drops per inch over an entire page in the manner a continuous tone printer like Dye Sublimation does. It will mix various colors, sizes and placements across the page to give the impression of continuous tone, but if you look close enough, you will still see the dither pattern.
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Hi,
My interpretation would be more that the dithering is optimised for 360 PPI and 720 PPI respectively. Would be much interesting to have Jeff's input on this.
This is actually quite important. Jeff's recommendation was to always print at 360 or 720 PPI and let Lightroom do the scaling.
Best regards
Erik
And you would be wrong. Jeff has tremendous empirical experience with Epson output, and following his tips will lead to great images, but he still believes that the image is resampled. He has finally accepted Epson's assertion that the driver doesn't do it, but now believes that the Operating System does it. While if you have a developers kit installed it is fairly easy to trace the data and prove otherwise, at least on the Windows Platform.
A dithering printer doesn't have a "Native" resolution. Epson printers have various increments of linear distance that it can put down a drop. But it will never put down a constant number of drops per inch over an entire page in the manner a continuous tone printer like Dye Sublimation does. It will mix various colors, sizes and placements across the page to give the impression of continuous tone, but if you look close enough, you will still see the dither pattern.
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The point on dithering is an interesting one - the printer's processor
1.) Takes in an image at whatever DPI
2.) If it's not at one of the standard DPIs (it seems like they may be 300/600 for Canon, 360/720 for Epson), resamples through a simple algorithm to those standard resolutions(Erik's post today suggests this may actually be part of step 3)
3.) Dithers to the variable dot-size pattern laid down in 11 or 12 colors at a very high resolution, so when it's viewed, it looks (without a loupe) like a continuous tone).
Regardless of whether the resample happens as part of the dither or in a separate step, there is no way of producing the dither without having a known relationship between pixels in the input datastream and area taken up on paper - there's an EFFECTIVE resample happening SOMEWHERE. Most good drivers (Lightroom's internal driver, QImage, ImagePrint (which also uses its own dither!)) eliminate that scaling step by sending the data at the correct size (performing an explicit resample with a more sophisticated algorithm). Except in the case of ImagePrint (which sends predithered data right to the head), the driver probably performs some sort of implicit scaling when dithering, but that scaling is meaningless because it's 1:1 with the image at the desired size
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It is not that simple in practice. MTFs do multiply, but one must convert from the spatial domain to a frequency domain by first performing a Fourier transform, multiply the MTFs, and then convert back to the spatial domain as explained by Norman Koren here (scroll down to the Imaging Systems section). Not being an expert in these matters, I don't how one would do this in practice.
I am not an expert either, but it turns out that it is not that difficult for a test image well focused in the center, captured with good technique all other things being equal. In such a case the final MTF in the center of the image is mainly the product of three (or four) MTF curves, of which two (or three) are well known: diffraction (as a function of f-number), pixel aperture (as a function of pitch) and lens blur (often unknown). If the sensor has an antialiasing filter the fourth MTF curve is the AA's (as a function of the spreading distance, easy to estimate). That's it.
So if you are measuring system MTF off a slanted edge in the center of the field of view, for instance, if only one variable is improved while keeping everything else the same (e.g. pitch is reduced) we can pretty well guarantee that it's going to improve the overall reading throughout the curve, in some parts more than in others. It's not too difficult to estimate approximately by how much in a given situation, but we'll leave that for another time.
Jack
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My interpretation would be more that the dithering is optimised for 360 PPI and 720 PPI respectively. Would be much interesting to have Jeff's input on this.
This is actually quite important. Jeff's recommendation was to always print at 360 or 720 PPI and let Lightroom do the scaling.
The point on dithering is an interesting one - the printer's processor
1.) Takes in an image at whatever DPI
2.) If it's not at one of the standard DPIs (it seems like they may be 300/600 for Canon, 360/720 for Epson), resamples through a simple algorithm to those standard resolutions(Erik's post today suggests this may actually be part of step 3)
3.) Dithers to the variable dot-size pattern laid down in 11 or 12 colors at a very high resolution, so when it's viewed, it looks (without a loupe) like a continuous tone).
Regardless of whether the resample happens as part of the dither or in a separate step, there is no way of producing the dither without having a known relationship between pixels in the input datastream and area taken up on paper - there's an EFFECTIVE resample happening SOMEWHERE. Most good drivers (Lightroom's internal driver, QImage, ImagePrint (which also uses its own dither!)) eliminate that scaling step by sending the data at the correct size (performing an explicit resample with a more sophisticated algorithm). Except in the case of ImagePrint (which sends predithered data right to the head), the driver probably performs some sort of implicit scaling when dithering, but that scaling is meaningless because it's 1:1 with the image at the desired size
This is the fallacy that the image is resampled at all! A continuous tone device must resample to it's native resolution because it is obligated to put a dot (pixel) of a specific color at a specific location with a set pitch to the next dot across the entire page. Assuming a 300dpi continuous tone printer, then the printer lays down 300 dots per inch across the entire page. To get from the total pixel dimensions given to the printer to printed output it must resample unless the resolution exactly matches the printer dpi x dimensions.
A dithering printer doesn't operate that way. It has a set of droplet locations per linear inch, droplet sizes and droplet colors at it's disposal. It also knows the characteristics of the media from the selection in the driver. From this data, it must create a pattern of dots varying is number, spacing, size and color to give the appearance that represents what the original data looks like. It might lay down 340 drops in one linear inch and then only 310 in the next measured linear inch. Epson printers do not lay down a consistent 360dpi or 720dpi. The settings for higher quality in an Epson driver are merely changing the constraints on the dither algorithm. That is it is allowing more locations to be used in the computation. However, that does not mean that in any linear inch, it will actually use all those available locations.
Bottom Line is if you follow Jeff's recommendations, you will get great output. My point is that because he believes the image is resampled, he neglects other options that might result in similar results consuming less resources or even better output. For example, assume you have an image at 480ppi. Jeff's recommendations would have you either down sample to 360ppi or up sample to 720ppi. He neglects the option of using 480ppi directly (even multiple of 60ppi) because he believes it will be resampled while Epson says it won't.
I've tested this with a 540ppi image that I printed at 540ppi, 360ppi and 720ppi. In general, I find essentially no difference in the images printed on Epson Exhibition Fiber or Epson Hot Press Bright. There have been images where I think I might have seen a difference, but couldn't really say one was better than the other and if you put the 3 side by side, I certainly don't think I could tell you which was which. Your eyes might say otherwise.
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This is the fallacy that the image is resampled at all!
Here we go again, we have discussed this before, you are still demonstrably not correct. Printer drivers do resample, as can be easily verified by printing a e.g. 359 PPI or 361 PPI image to the same dimensions, but now at 360 PPI. Use a simple 1 pixel wide alternating vertical black and white line pattern across a reasonable width of the image and the printed result will show aliasing, completely predictable and consistent with resampling. A 361 PPI image at 10 inches wide would be 3610 pixels wide. try printing those 3610 pixels over a width of exactly 10 inches at 360 PPI. Those 3610 pixels will need to be squeezed into the grid for 3600 pixels, which is done by resampling, and aliasing is the result. If there is no resampling, there would be no aliasing.
The simple experiment has been performed by several people here on LuLa, and the outcome was, ... aliasing. The only way to mitigate the issue is by using additional dithering to the output data, i.e. on top of the normal dithering for intermediate ink colors.
A bit more background on the differences between Mac OS and Windows printer drivers is discussed here (http://forum.luminous-landscape.com/index.php?topic=90225.msg737098#msg737098).
If you really want to torture test your printer's capabilities, which includes detection of head-alignment and paper transport issues, feel free to use my printer and output medium test target, as described here (http://forum.luminous-landscape.com/index.php?topic=99905.msg818035#msg818035).
Cheers,
Bart
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The two images show nearly as much difference as the two captured with the great lens. No, the sharp image is not as sharp, but the degree of improvement is NOT that different. I'm assuming his test conditions were decent, although he doesn't go into any detail, he's been around the Canon world a long time, and is well respected....
Hello Dan,
I am not surprised...
if we look at sharpness only;
The center of most lenses are usually able to do 50MP when stopped down. It is the sides that make the difference...
Even good lenses have problems at 36MP at the sides of full frame- not to mention the corners...
To show you the resolution of a good lens in the central area i attach two 100% central crops -A and B - both shot with the same good lens - the nikkor 45mm PCE @F8
A is taken with a Nikon1-J5 20MP and B taken with a D810 ( 36MP full frame) and Upsampled to the size of the Nikon1-J5 output.
the Nikon1 J5 captures the central 13,2 x 8,8 mm area and with this resolution a full frame sensor would be 154 MP.
As you can see the quality is really good even @ 150MP!
In the case of this lens i can even make an almost fully shifted image with the nikon1-J5 that looks good.
(@ f5.6 the central sharpness is even better, but shifted it is less)
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Here we go again, we have discussed this before, you are still demonstrably not correct. Printer drivers do resample, as can be easily verified by printing a e.g. 359 PPI or 361 PPI image to the same dimensions, but now at 360 PPI. Use a simple 1 pixel wide alternating vertical black and white line pattern across a reasonable width of the image and the printed result will show aliasing, completely predictable and consistent with resampling. A 361 PPI image at 10 inches wide would be 3610 pixels wide. try printing those 3610 pixels over a width of exactly 10 inches at 360 PPI. Those 3610 pixels will need to be squeezed into the grid for 3600 pixels, which is done by resampling, and aliasing is the result. If there is no resampling, there would be no aliasing.
The simple experiment has been performed by several people here on LuLa, and the outcome was, ... aliasing. The only way to mitigate the issue is by using additional dithering to the output data, i.e. on top of the normal dithering for intermediate ink colors.
A bit more background on the differences between Mac OS and Windows printer drivers is discussed here (http://forum.luminous-landscape.com/index.php?topic=90225.msg737098#msg737098).
If you really want to torture test your printer's capabilities, which includes detection of head-alignment and paper transport issues, feel free to use my printer and output medium test target, as described here (http://forum.luminous-landscape.com/index.php?topic=99905.msg818035#msg818035).
Cheers,
Bart
The 359ppi and 361ppi test is specifically demonstrating the data handling phenomena that occurs because the driver works in 60 x 60 pixel blocks of data. It is specifically why even multiples of 60 have been recommended since 1994. It is why Epson recommends a minimum of 180ppi (even multiple of 60) for quality output. Neither the OS, nor the DRIVER resamples the image! Epson has been vehement about this since the original printer! Even Jeff finally relented and now blames the supposed resampling on the OS.
Print 2 samples one at 300 and one at 360 and look at the differences. They will not exhibit the same phenomena! In fact, print at 330 and you won't get that either.
At the end of the day, it really doesn't matter. Most people will just follow the rule that the printers algorithm tops out at 360ppi and will use that. Others will upsample to 720ppi which is another multiple of 60 and it won't matter and the rest will use even multiples of 60 from what they have to 720ppi as the mood strikes them. No one is going to be foolish enough to send 359ppi or 539pp to the printer.
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If what you say is true and no resampling is occurring, why would using even numbers of 60 be important? We’ve always be led to believe that the native dpi of the epson driver is 360 so using numbers that divide evenly by 60 yields the best results.
Also curious what would cause the aliasing in Bart’s test other than resampling ? there have been other examples of this discussed here.
Again, you are right it doesn’t really matter, best practice is to use good program to get the data to 360 before sending it to the printer. Just sort of curious.
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If what you say is true and no resampling is occurring, why would using even numbers of 60 be important? We’ve always be led to believe that the native dpi of the epson driver is 360 so using numbers that divide evenly by 60 yields the best results.
Sounds like yet another urban legend, to me anyway. Integer divisions of 360 (360/2=180, 360/3=120, 360/4=90, 360/5=72, 360/6=60, etc. ) will produce evenly spaced aliasing patterns, almost like an intended pattern (instead of uniform gray, the average between black and white). Maybe that looks more acceptable, but it is still aliasing caused by maximizing and minimizing the contrast when the resizing happens to align/aliase with the grid.
Cheers,
Bart
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Some print resolution number trivia…
Begin with a Hasselblad sensor size of 40 Megapixels (5478 x 7304),
Specify a gallery print size of 40x50.333 inches (keeping the exact 3x4 aspect ratio) @ 180 ppi,
Result file pixel size will be 7200x9600 =
Coincidentally numbers used in Epson printer model names?
Many common aspect ratios such as 2x3 to make 20x30, 30x45, 40x60; 3x4 to make 20x32, 30x40, 40x53.333; 4x5 to make 24x30, 40x50, 48x60, etc., @ 180, 240, and 360ppi can result in curious number revelations too.
An amazing feat is that the engineers can design & manufacture something as small as a Canon sensor to an exact 2x3 aspect ratio and I can then enlarge those individuals rows and columns of pixels to a 40x60 to a machine such as an Epson 11880 to deliver a print to the exact size. Amazing because…
…sometimes machines are not so behaved and accurate. There is sometimes an ugly truth called print size/length compensation, print size calibration, print size off-set, print scale correction, media advance calibration, scale adjust, etc., common especially to users of professional printers making rather long prints. Most RIPs have this control and it’s often a moving target.
Pixel stretching? I think the engineer's term is subsampling.
Using subsampling, a continuous-tone devices such as Fuji Frontier, Noritsu, Lightjet, Chromira, Lambda can deliver discernible individual red, green, and blue pixels on a white, gray, or black background @ their native resolutions. Usually somewhat soft however because of subsampling and halation but still amazing especially if any print size compensation is involved, as it usually is.
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...The two images show nearly as much difference as the two captured with the great lens. No, the sharp image is not as sharp, but the degree of improvement is NOT that different. I'm assuming his test conditions were decent, although he doesn't go into any detail, he's been around the Canon world a long time, and is well respected.
Back to the OP, wouldn't it have been more interesting to see the 6D images interpolated instead of merely upscaled? Especially the 'lousy lens', I am not sure that we are reacting more to the blockiness than to the information.
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Back to the OP, wouldn't it have been more interesting to see the 6D images interpolated instead of merely upscaled? Especially the 'lousy lens', I am not sure that we are reacting more to the blockiness than to the information.
Yes, good point. It was also mentioned by others, that the upscaling/interpolation method (and subsequent sharpening) can make a difference as well.
Cheers,
Bart
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Sounds like yet another urban legend, to me anyway. Integer divisions of 360 (360/2=180, 360/3=120, 360/4=90, 360/5=72, 360/6=60, etc. ) will produce evenly spaced aliasing patterns, almost like an intended pattern (instead of uniform gray, the average between black and white). Maybe that looks more acceptable, but it is still aliasing caused by maximizing and minimizing the contrast when the resizing happens to align/aliase with the grid.
Cheers,
Bart
It's pretty outdated now, but I believe when it was popular several years ago (should have indicated that in my post I was talking about an outdated concept), the theory was the epson driver resizing was weak so forcing it to be an even number would give the best results. I think the other popular thing back then was to enlarge it was better to do so at 10% increments up to the final size. but the concept came from the idea that somewhere in the pipeline the image would be resized to the machines "internal" dpi of 360 or 720.
I think most now resize to either 360, either by creating a secondary file or using something like LR. And as you pointed out, that doesn't eliminate aliasing, just sort of create different type of aliasing.
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This issue always ends up being confused when people treat PPI and DPI as the same thing. There is no 1:1 relationship between pixels and printer dots except, perhaps, in pure tones of the printer's inkset and even then, it depends on so many things that it's very unlikely.
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If what you say is true and no resampling is occurring, why would using even numbers of 60 be important? We’ve always be led to believe that the native dpi of the epson driver is 360 so using numbers that divide evenly by 60 yields the best results.
Also curious what would cause the aliasing in Bart’s test other than resampling ? there have been other examples of this discussed here.
Again, you are right it doesn’t really matter, best practice is to use good program to get the data to 360 before sending it to the printer. Just sort of curious.
It's the boundary conditions surrounding the 60x60 macro blocks of data. 359 and 361 end up being 1 pixel off an even multiple of 60. No one ever tries it at or 479/481 or 539/541 because of the wide spread belief that the printer resamples the image to 360.
There are really only 3 things that one can believe:
1. No resampling occurs - One is then obligated to explain the phenomena that happens with images at 359ppi for example.
2. The Driver Resamples the image - One is obligated to believe that Epson has been lying for years!
3. The OS (Mac and Windows) resample the image - One is obligated to believe that Apple and Microsoft colluded with Epson to have their respective OS resample images to 360ppi and 720ppi rather than some other resolution or not resample at all. This one is just a little conspiracy theory nutty for me.
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Forget about 300, 360, 600, 720, etc. dpi. How about 127,000 dpi?
http://fortune.com/2015/12/17/smallest-artwork-printing-mona-lisa/?xid=smartnews
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Hi Slobodan,
What would the standard viewing distance be? Also, I think they need to put some effort in generating colour profiles for that device…
Best regards
Erik
Forget about 300, 360, 600, 720, etc. dpi. How about 127,000 dpi?
http://fortune.com/2015/12/17/smallest-artwork-printing-mona-lisa/?xid=smartnews
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Forget about 300, 360, 600, 720, etc. dpi. How about 127,000 dpi?
http://fortune.com/2015/12/17/smallest-artwork-printing-mona-lisa/?xid=smartnews
That article makes the common mistake of not differentiating between PPI and DPI. It states that the common inkjet office printer operates at 300 DPI. As an example, my Epson 3880 is fed images with a resolution of 360 or 720 pixels per inch (PPI). Unlike a contone printer, it does not lay down the pixels at these resolutions, but uses an error diffusion process to lay down dots of ink and the addressable resolution for placement of these dots is 2880 x 1440 dots per inch (DPI). The placement of the dots is semi-random and not in a fixed pattern. The printer can produce 3 different sizes of droplets, with the smallest droplet measuring 3.5 picoliters. Once the droplet is laid down, there is a certain amount of ink spread on the paper and the actual diameter of the droplet on the paper is not stated. The actual resolution of the print is fairly indirect.
Regards,
Bill
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Hi Bill,
I think Slobodan is just a bit sarcastic, in a quite pleasant manner, I may add :-)
One small consideration that has crossed my feeble mind is that many of us discussing PPI and resolution may have passed the age when we had optimum vision. Could be that we are discussing the number of angels dancing on the head of a pin, but without actually being able to observe any of those angels presuming they would exist?
Best regards
Erik
Ps. Just a general reflection, nothing personal…
That article makes the common mistake of not differentiating between PPI and DPI. It states that the common inkjet office printer operates at 300 DPI. As an example, my Epson 3880 is fed images with a resolution of 360 or 720 pixels per inch (PPI). Unlike a contone printer, it does not lay down the pixels at these resolutions, but uses an error diffusion process to lay down dots of ink and the addressable resolution for placement of these dots is 2880 x 1440 dots per inch (DPI). The placement of the dots is semi-random and not in a fixed pattern. The printer can produce 3 different sizes of droplets, with the smallest droplet measuring 3.5 picoliters. Once the droplet is laid down, there is a certain amount of ink spread on the paper and the actual diameter of the droplet on the paper is not stated. The actual resolution of the print is fairly indirect.
Regards,
Bill
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I think you guys are not seeing the breakthrough clearly (pardon the pun):
Researchers at the Technical University of Denmark have printed a color copy of the Mona Lisa that fits snugly into one pixel on an iPhone 6 screen.
My understanding is they managed to squeeze 127,000 pixels into one inch.
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I think you guys are not seeing the breakthrough clearly (pardon the pun):
My understanding is they managed to squeeze 127,000 pixels into one inch.
Did they lay down pixels or dots?
Bill
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Hi Bill,
I think Slobodan is just a bit sarcastic, in a quite pleasant manner, I may add :-)
One small consideration that has crossed my feeble mind is that many of us discussing PPI and resolution may have passed the age when we had optimum vision. Could be that we are discussing the number of angels dancing on the head of a pin, but without actually being able to observe any of those angels presuming they would exist?
Best regards
Erik
Ps. Just a general reflection, nothing personal…
Man, first you gotta see the pin!
Rob C
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Did they lay down pixels or dots?
Bill
Worst case, it is 127,000 vs. 2,880. Bodes well for the future of printing in any case.
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It's pretty outdated now, but I believe when it was popular several years ago (should have indicated that in my post I was talking about an outdated concept), the theory was the epson driver resizing was weak so forcing it to be an even number would give the best results.
Hi Wayne,
Actually, things look pretty bleak even nowadays. The resampling still seems to be crude (and thus simple to implement and fast and requires little driver or dithering firmware intelligence). This coarse (bilinear?) resampling is only causing part of the loss of quality.
I think the other popular thing back then was to enlarge it was better to do so at 10% increments up to the final size. but the concept came from the idea that somewhere in the pipeline the image would be resized to the machines "internal" dpi of 360 or 720.
The step resampling kind of worked, because the halos and ringing at higher detail level (still larger sizes than final) was kind of offsetting the loss of contrast of the next step down. But much better quality can already be achieve in a single step by using more complex algorithms.
I think most now resize to either 360, either by creating a secondary file or using something like LR. And as you pointed out, that doesn't eliminate aliasing, just sort of create different type of aliasing.
Yes, 360 PPI (which is printed with much higher DPI dot or droplet placement resolution) is approx. consistent with the acuity of human vision at reading distances in adequate illumination conditions. However, there are benefits to resampling to 720 PPI or, to get back to the original questions, shooting at higher resolutions even if the lens is a relatively modest performer, in order to allow capture and printing at 720 PPI rather than having to upsample.
Attached I've added a couple of sample patterns (TIFFs in 16-b/ch Adobe RGB colorspace). I've also added direct links in case the TIFFs do not attach/display well.
1. A sinusoidal cycle sweep going from effectively a 180 PPI resolution (~=3.54 cy/mm) to a 360 PPI resolution (~=7.09 cy/mm) at the top of the image, sampled at a 360 PPI resolution. This one should be printed at 360 PPI on Epson printers (with the 'Finest detail' option switched off), and would measure (720 pixels @ 360 per inch =) 2 inches in length. Direct link to original file (https://www.dropbox.com/s/udzchcgbmsqqq2s/cymmsweep_180-360PPI_at360PPI.tif?dl=0)
2. The same sinusoidal cycle sweep, but now sampled at 720 PPI resolution. It's as if we used the same lens but with a sensor that has twice the resolution, well, sort of. This one should be printed at 720 PPI on Epson printers (with the 'Finest detail' option switched on), and would also measure (1440 pixels @ 720 per inch =) 2 inches in length. Direct link to original file (https://www.dropbox.com/s/to4zk7sdtg88zrc/cymmsweep_180-360PPI_x200pct_at720PPI.tif?dl=0)
The difference in output quality may or may not be clearly visible in print (depending on paper used and how well the head alignment and paper transport is calibrated), but when pixelpeeping the files, e.g. at the top righthand corner, it should be clear that the pattern at the maximum 360 PPI effective 'captured' resolution is much more accurately defined in the 720 PPI file version, and thus much easier to print and sharpen well (even if the printer driver+OS resampling is a bit lacking). So capturing with a higher resolution sensor, even of a modestly performing lens (360 PPI on a 720 PPI capable resolution) is worthwhile.
This oversampled image capture will also allow much better capture sharpening at the higher resolution. We may even benefit from upsampling the lower resolution image, and sharpening that (more accurately because more pixels to do it smoothly for intermediate tones).
Oh, and while we are on this lateral (but related) discussion of print resolution, printing at 720 PPI will of course allow to print twice the resolution, which means we can use half the viewing distance, or print twice as large, without visual loss. This assumes that the lens+sensor are able to capture enough detail. Stitching may be needed t achieve large output, but that's always an option (if the subject matter allows).
Cheers,
Bart