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10-18-2015, 11:08 PM   #61
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QuoteOriginally posted by biz-engineer Quote
If you read this post, could you please add the settings (such as aperture, focal length and distance to subject), you used for your K-3II / 6D experiment ? Yesterday I was out with my K-3 for stitching but was hard to get everything sharp, due the DoF. When considering APSC vs FF, does diffraction catch-up faster than DoF ? I mean, for the same DoF on FF, the aperture should be one stop smaller, which at f16 introduces diffraction. Just wondering how to manage DoF trade-off , especially when going up to MF.


For 24x36 [full frame], the maximum circle of confusion is about 1.5 times as large as that for a 1.5 crop factor sensor. This means that there is little difference in the relationship between depth of field and diffraction for different formats. In other words, a lens can be stopped down one more stop on full frame [resulting in similar DOF] than can on APS-C before diffraction limits resolution.

10-19-2015, 10:27 AM   #62
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QuoteOriginally posted by civiletti Quote
For 24x36 [full frame], the maximum circle of confusion is about 1.5 times as large as that for a 1.5 crop factor sensor. This means that there is little difference in the relationship between depth of field and diffraction for different formats. In other words, a lens can be stopped down one more stop on full frame [resulting in similar DOF] than can on APS-C before diffraction limits resolution.
Since the diffraction limit on both APS-c and FF is somewhere between ƒ5.6 and ƒ8 that is somewhat misleading. ƒ8 on APS-c while over the limit is still good. ƒ11 on FF is past the famous drop off point, and similar to ƒ11 on APS-c. ƒ5.6 is optimum on both. In this case the FF doesn't gain from having a larger sensor.

Notice that on FF and APS-c the graphs are pretty much the same. Peak at ƒ5.6, still pretty good at ƒ8 measurable drop off at ƒ11.





However, these are completely different systems, I'd love to see graphs for a K-3 and a D750, but I don't have a source for that. But stuff like this suggests, that with a D750 being 200 line pairs better than a K-3 and the D750 @ƒ11 being softer than a K-3 @ ƒ8, the diffraction limit might actually allow the K-3 to catch up in total IQ after ƒ 5.6, even though technically it would be starting at a disadvantage, with both systems at ƒ5.6.

Last edited by normhead; 10-19-2015 at 10:39 AM.
10-19-2015, 06:51 PM   #63
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QuoteOriginally posted by normhead Quote
Since the diffraction limit on both APS-c and FF is somewhere between ƒ5.6 and ƒ8 that is somewhat misleading. ƒ8 on APS-c while over the limit is still good. ƒ11 on FF is past the famous drop off point, and similar to ƒ11 on APS-c. ƒ5.6 is optimum on both. In this case the FF doesn't gain from having a larger sensor.

Notice that on FF and APS-c the graphs are pretty much the same. Peak at ƒ5.6, still pretty good at ƒ8 measurable drop off at ƒ11.





However, these are completely different systems, I'd love to see graphs for a K-3 and a D750, but I don't have a source for that. But stuff like this suggests, that with a D750 being 200 line pairs better than a K-3 and the D750 @ƒ11 being softer than a K-3 @ ƒ8, the diffraction limit might actually allow the K-3 to catch up in total IQ after ƒ 5.6, even though technically it would be starting at a disadvantage, with both systems at ƒ5.6.

Check out the diffraction calculator here: Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks


Also: "Now what happens when we compare two different formats? Let's consider a lens of any focal length and aperture projecting an image on either a FF or Canon APS-C focal plane. The physical size of the diffraction blur pattern will obviously be the same on either focal plane. However, this is a bigger issue for the APS-C format, because the blur pattern is exactly 1.6 times larger in relation to the total image size, as compared to the FF image. To correct for this APS-C disadvantage, a 1.6 times larger aperture must be used -- approx. 1.36 stops."


Graphic Fusion : On Comparing Full Frame and APS-C DSLR Camera Formats, by Hampton Roads Photographer Sarah Fox


[The crop factor would be 1.5, not 1.6, for Pentax.]
10-19-2015, 11:23 PM   #64
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QuoteOriginally posted by normhead Quote
However, these are completely different systems, I'd love to see graphs for a K-3 and a D750, but I don't have a source for that. But stuff like this suggests, that with a D750 being 200 line pairs better than a K-3 and the D750 @ƒ11 being softer than a K-3 @ ƒ8, the diffraction limit might actually allow the K-3 to catch up in total IQ after ƒ 5.6, even though technically it would be starting at a disadvantage, with both systems at ƒ5.6.
Diffraction itself is independent from the format and is additive. Yes, the charts make sense, relative to peak lens sharpness, diffraction impact for the same relative amount both on APSC and FF sensors. However, @f11, FF resolves 3423 lw/ph (very good) while @f11 APSC resolves 1991 lw/ph ( fair ). For a FF enlargement made 1.5x enlargement of APSC, the result would be the same, but for the same print size, FF would in principle show less of the diffraction effect. However, what comes into play is the AA filter mandatory on a "low resolution" FF sensor, and lack of AA filter on the "high resolution" APSC sensor.


Last edited by biz-engineer; 10-19-2015 at 11:29 PM.
10-20-2015, 04:45 AM - 1 Like   #65
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QuoteOriginally posted by biz-engineer Quote
Diffraction itself is independent from the format and is additive. Yes, the charts make sense, relative to peak lens sharpness, diffraction impact for the same relative amount both on APSC and FF sensors. However, @f11, FF resolves 3423 lw/ph (very good) while @f11 APSC resolves 1991 lw/ph ( fair ). For a FF enlargement made 1.5x enlargement of APSC, the result would be the same, but for the same print size, FF would in principle show less of the diffraction effect. However, what comes into play is the AA filter mandatory on a "low resolution" FF sensor, and lack of AA filter on the "high resolution" APSC sensor.
These are not same the same MP sensors. We know that a K-3 resolves about 2700 lp/ph.. a D750 resolves around 2900. Just looking at a D750 and a K-3 it's quite possible the small difference Ian pointed out would disappear once you match DoF over ƒ5.6. There are many other scenarios that could also come into play. More expensive lenses like the 31 ltd. peak at ƒ4. A D810 will resolve more than 4000 lw/ph. which would be about a third more than a K-3, which is pretty standard for Sony sensors, however there are Canon pro setups, and setups like the D4x, that somehow achieve a higher lw/ph on a relatively smaller sensor. A fact I've never seen discussed by the theorists on the forum. The reality is just way more complicated than any theory I've seen put forward. SO, I take the easy way out, just look at the pictures.... I'm not about to develop the unified theory of digital photography.

QuoteQuote:
Also: "Now what happens when we compare two different formats? Let's consider a lens of any focal length and aperture projecting an image on either a FF or Canon APS-C focal plane. The physical size of the diffraction blur pattern will obviously be the same on either focal plane. However, this is a bigger issue for the APS-C format, because the blur pattern is exactly 1.6 times larger in relation to the total image size, as compared to the FF image. To correct for this APS-C disadvantage, a 1.6 times larger aperture must be used -- approx. 1.36 stops."
The numbers don't bear her out and she lists no qualifications for making this kind of assessment. That would be like me writing a page, putting it up on the internet and then quoting it. What she doesn't understand about diffraction is that diffraction is not really an issue until it is is above .7 pixels and doesn't really affect resolution until it is somewhat more than that. So if you were looking at ƒ8 on APS-c and ƒ8 on FF, assuming that neither images has diffraction at more than about .7 pixels, there will be no theoretical difference, regardless of magnification etc. because the base unit in digital photography is the pixel. Phenomena that have effect at less than .7 pixels are irrelevant for micro-contrast, and phenomena that effect less than somewhere in the neighborhood of 1.2 to 1.5 pixels are irrelevant for resolution. This is where those who do not test their photographic hypothesis really get into trouble. Her logic is un-assailable, until you get to the part where she doesn't really understand how a camera system works... and then it falls apart. Anyone who has looked at the IR images for various cameras, knows what she claims isn't true. Her theory is fine waste of internet space.

Your first clue is, while she prints a whole page she actually has not one comparison image to back up her point. There's a reason for that. She's not a scientist, she's a photographer trying to convince you to hire her based on the "My camera is better than yours " line of thought. The "You have to have a Full Frame to be a pro" thinking. Since most people have neither a Full Frame nor the technical knowledge to understand how wrong she is, it can be a very lucrative strategy. But, it's not science. Science requires empirical evidence.

Or to put it more succinctly... "Just show me some images that demonstrate what you're talking about. What no pictures? Then you have no empirical evidence and we have nothing to discuss."

I prefer to work the other way. Start with an observation, try and come up with a theory that explains it. If there is no un-biased empirical evidence on page one of your thesis, nothing you say after that makes any sense. It's just mental masturbation. Maybe it feels good, but it's not science.

Last edited by normhead; 10-21-2015 at 08:27 AM.
10-21-2015, 12:22 AM   #66
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QuoteOriginally posted by normhead Quote
I prefer to work the other way. Start with an observation, try and come up with a theory that explains it.



That is what the people who developed the optical science did. The math, at least for comparison is fairly simple. The airy disc of a lens at a particular aperture and light wavelength will be the same regardless of camera sensor format. That should be easy to understand: the interaction between a pixel and the light hitting it does not depend on how many pixels surround the one in question. When an image from an APS-C camera is enlarged 1.5 times as much a similar image from a full frame camera, visible diffraction is going to increase. Whether you have noticed that in prints or on displays does not change the rule. Of course, image quality is a complex situation, but the effect of lens diffusion is not very complex.
10-21-2015, 08:37 AM - 1 Like   #67
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QuoteOriginally posted by civiletti Quote
That is what the people who developed the optical science did. The math, at least for comparison is fairly simple. The airy disc of a lens at a particular aperture and light wavelength will be the same regardless of camera sensor format. That should be easy to understand: the interaction between a pixel and the light hitting it does not depend on how many pixels surround the one in question. When an image from an APS-C camera is enlarged 1.5 times as much a similar image from a full frame camera, visible diffraction is going to increase. Whether you have noticed that in prints or on displays does not change the rule. Of course, image quality is a complex situation, but the effect of lens diffusion is not very complex.
Civiletti.. you are the one changing the rule. The problem is you've taken a much too simplistic approach to the rule. And the fact that you have no images to demonstrate what you are talking about just proves it.

Here is the problem...."visible diffraction is going to increase". The first question you have to ask yourself is, "Is there visible diffraction." And the answer is , if the diffraction is less than a pixel, then the answer is no. And the point becomes moot.

So, many of these types of simplified theoretical discussions could be clarified, with the presentation of a couple of images. Instead they rage on for hours and weeks. As I see it , this is just sheer laziness. As is your statement "That is what the people who developed the optical science did." How do we know you are correctly interpreting what they said, or are applying it correctly to camera technology. You don't, and I don't, and you refuse to take even the most basic steps, like snapping a couple of photos to find out if you do. Instead you quote some pro's advertising.


Here's a few other things to consider at 1:1 pixel peeping one of these is a K-3 and one is a D750.

First look at web size, the image has been reduced so much, about 5:1 any possible effect from diffraction on either image is pretty much invisible. You can't tell which is which.



Pixel peeping you can see a very small difference. Now that very small difference shown at a size of 65x44, is the diffraction difference you are discussing. And to magnify it, you'd have to go over that size, pretty much a non-issue don't you think?


To see the whole image at that size, and to see that difference, you'd have to print 65 inches by 44 inches, and there is still no guarantee that the printer would produce different prints, it would depend on how accurate the printer was it reproducing minute differences in detail.

So this is the critical point of reference, at what point in a current camera system does any possible difference in diffraction become visible to the point it would negatively affect an image. And until you know that, you don't know anything practical.

There is a constant war of words, between those, who think they know something because they've read some amateur physicist , and those who spend time actually analyzing images. The question you should be trying to answer is "how is it possible that you can compare an image from a k-3 and an image from a 6D or D610, or even D750 without seeing any difference in IQ?" Why does the 1.5 magnification not make a difference? When you understand that, then you understand the correct way to apply optical physics to camera systems.

IN this case, the answer is, you are not enlarging diffraction with a K-3 until you go over 65 inches by 44 inches. Up until that point, say if you reduce the image to 4000 x 3000, you are actually doing the opposite. You are reducing the size of the image, and making the images more and more similar. That tiny bit of extra clarity in the D750 image, gets reduced, until it becomes visually imperceptible. That is what the images tell you, that your quoted source doesn't.

I know what comes next. Spin doctors come on and attack the images, Imaging resources who provide the images, the cameras used, the methodology of the test, the lenses used and my mother's heritage, so that they can remain in denial. I don't know how folks get so attached to these ideologies but they do. But, from my perspective, there is simply no excuse for it.

Look at a couple images, it's critical for you to understand what you are talking about. Looking at good comparative images and providing them to your readers, is not optional. If it doesn't exist in the real world, it doesn't exist.

I totally get that a fastidious person, like Ian, looks at the two images and thinks, I have to have the D750. But most of us simply don't look at 65"x44" inch images, and see no value in paying a lot of money for a little bit of extra clarity on 96 inch prints, (where it might make a difference) because, we don't make 96 inch prints. I sell my prints at 30"x20", and no one has ever come to me and said "I'd like a larger version of that print." I live well below the cut off point where owning a D610 or D750 would even theoretically make a difference, forget about there being much possibility of a practical difference.

Last edited by normhead; 10-21-2015 at 09:55 AM.
10-21-2015, 10:52 AM   #68
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The aperture settings are missing for K-3 and D750, so, the image-resource comparison can't be considered as a valid proof of equivalence between the K-3 and D750, as far as diffraction is concerned. Even if the airy disc of diffraction is smaller than a pixel, each ray of light diffracted does not decide to align to each pixel, diffraction consists of a loss of contrast of the incoming continuous signal domain, and since pixels are part of a discrete sampling process, whatever the amount of diffraction, diffraction is present in every pixel as an added error versus a diffraction free image. However, it becomes visible at 100% crop when the amount of blur is relatively significant (relative to the enlargement). From crossing the element of the lens up to the digital domain (after analog to digital conversion) and even up to JPEG compression, errors (lens aberrations, diffraction, reflections, special folding (residual moiré), thermal noise, flicker noise, dark current, sense amp noise, and quantization errors, JPEG compression loss) end-up in the final image...

10-21-2015, 11:07 AM - 1 Like   #69
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QuoteOriginally posted by normhead Quote
I know what comes next. Spin doctors come on and attack the images, Imaging resources who provide the images, the cameras used, the methodology of the test, the lenses used and my mother's heritage, so that they can remain in denial. I don't know how folks get so attached to these ideologies but they do. But, from my perspective, there is simply no excuse for it.
QuoteQuote:
The aperture settings are missing for K-3 and D750,
Read the exif, Imaging Resource "Comparometer" , all exif data are known and published, in this case ƒ8, the lens used is a 70mm Sigma macro where ever possible because it is available for most mounts. If the results had been normalized the for DoF, the K-3 would have been sharper as it would have been shot at ƒ5.6, but only marginally so. Especially if diffraction is the issue.

QuoteQuote:
so, the image-resource comparison can't be considered as a valid proof of equivalence between the K-3 and D750, as far as diffraction is concerned.
But it can be used until someone comes up with something better. Any relevant data is better than no data. Which is what this criticism presents.

Or in case you missed it, I'm not really interested in a view point, unsubstantiated by any data. And data in photography is not the theories of optical physics, but images.The fact that something may not be entirely relevant must be tempered by the fact, that it might be the best available. And if I'm working with the best available, I'm still way ahead of everyone working with nothing, or a partially understood theory published somewhere on the internet.

It would be so much easier if before people published their thoughts, they would take a second and think..." is this a testable theory, and how would I test it? " And then go out and do it before they publish, instead of reciting pablum.

Personally, if I don't find a set of images somewhere to demonstrate what I'm saying, I don't put it here. And I don't listen to people with opinions for which they have nothing, but some wive's tale kind of reasoning.

Just saying "you might not be right because of these reasons" doesn't mean I'm not right. It means I might not be right. But I'm at an advantage if I have actual images that support what I'm saying. Where as those casting doubt...what are they actually offering? Support for some really bad reasoning based on my research not meeting their standards? When their own standards of criticism is that hey don't need to have anything? It's an odd world.

Those who seek, harassed by those who don't.

Last edited by normhead; 10-21-2015 at 04:21 PM.
10-21-2015, 11:22 AM   #70
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QuoteOriginally posted by normhead Quote
But it can be used until someone comes up with something better. Any relevant data is better than no data. Which is what this criticism presents.
That's for sure ! Models are proxies only of reality when the cost of doing experiments is too costly versus experimentation (example of flight simulators, or finite element models for assessing the strength of materials for road bridges... anyway the models are partially or totally built from experimentation at smaller manageable scales). However, we always finalize by physical trials / experiments to tune what was not covered by the models.

In the case of cameras, getting images from others or test charts is relatively cheap and safe (unless the camera would explode), so, using theory for consumer digital imaging is mostly for fun or defending an opinion. A picture is worth a thousand words. We should compare a K-3 and D750 images at f22 :-)
10-21-2015, 11:41 AM   #71
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QuoteOriginally posted by biz-engineer Quote
That's for sure ! Models are proxies only of reality when the cost of doing experiments is too costly versus experimentation (example of flight simulators, or finite element models for assessing the strength of materials for road bridges... anyway the models are partially or totally built from experimentation at smaller manageable scales). However, we always finalize by physical trials / experiments to tune what was not covered by the models.

In the case of cameras, getting images from others or test charts is relatively cheap and safe (unless the camera would explode), so, using theory for consumer digital imaging is mostly for fun or defending an opinion. A picture is worth a thousand words. We should compare a K-3 and D750 images at f22 :-)
In my experience ƒ22 is the limit of usefulness for APS-c while ƒ32 is the limit for FF, which is about right because ƒ22 on APS-c is the same DoF as ƒ32 on FF, but both are really soft, so what would be the point? But realistically, I try and shoot at ƒ5.6 with all my lenses, because it's where all the lenses that I own are sharpest, (Those top notch lenses that are sharpest at ƒ4 like the 31 ltd. so far are beyond my reach).so ƒ22 is not an area, I choose to explore. I would recommend everyone when trying out a lens take an image of an appropriate test subject at every ƒ-stop, just to get a feeling for what you lose and what you gain. Occasionally ƒ16 is useful on APS-c, just as occasionally ƒ22 is useful on FF.

Last edited by normhead; 10-21-2015 at 04:16 PM.
10-21-2015, 12:14 PM   #72
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QuoteOriginally posted by normhead Quote
Occasionally ƒ16 is useful on APS-c, just as occasionally ƒ22 is useful on FF.
I also found that f5.6 deliver the best sharpness, so, like you, I also tend to use f5.6. But the only reason why I want to use up to f22 is to increase the depth of field for macro or landscape when there is foreground and I want both the foreground and background sharp. When I take several shots with a longer lens, it is equivalent to have a larger camera sensor, but the hyper-focal distance of the longer lens also means I have to stop down to get a larger depth of field. I figured out that there is no choice, but a trade-off between diffraction (with a high f-number) or less depth of field. But it seems that a tilt-shift lens can help, or we should resort to focus stacking, whatever camera format we use.
10-21-2015, 04:18 PM   #73
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QuoteOriginally posted by biz-engineer Quote
I also found that f5.6 deliver the best sharpness, so, like you, I also tend to use f5.6. But the only reason why I want to use up to f22 is to increase the depth of field for macro or landscape when there is foreground and I want both the foreground and background sharp. When I take several shots with a longer lens, it is equivalent to have a larger camera sensor, but the hyper-focal distance of the longer lens also means I have to stop down to get a larger depth of field. I figured out that there is no choice, but a trade-off between diffraction (with a high f-number) or less depth of field. But it seems that a tilt-shift lens can help, or we should resort to focus stacking, whatever camera format we use.
I always shoot macro shots at , 2.8, 5.6, 11 and 16, and pick the one I like. It's really hard to anticipate which will be the image.. and occasionally the stars align and a ƒ2.8 narrow DoF image works best.
10-21-2015, 05:16 PM   #74
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QuoteOriginally posted by Rupert Quote
Very interesting! I'm impressed. When you can show me a huge print with a pixel shifted squirrel...I'm a buyer!

Regards!
I know of a stuffed squirrel nailed to a post on a hillside in the Garden of the Gods. I wonder if it is still there???
10-21-2015, 08:22 PM   #75
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QuoteOriginally posted by normhead Quote
Civiletti.. you are the one changing the rule. The problem is you've taken a much too simplistic approach to the rule. And the fact that you have no images to demonstrate what you are talking about just proves it.

Here is the problem...."visible diffraction is going to increase". The first question you have to ask yourself is, "Is there visible diffraction." And the answer is , if the diffraction is less than a pixel, then the answer is no. And the point becomes moot.

So, many of these types of simplified theoretical discussions could be clarified, with the presentation of a couple of images. Instead they rage on for hours and weeks. As I see it , this is just sheer laziness. As is your statement "That is what the people who developed the optical science did." How do we know you are correctly interpreting what they said, or are applying it correctly to camera technology. You don't, and I don't, and you refuse to take even the most basic steps, like snapping a couple of photos to find out if you do. Instead you quote some pro's advertising.


Here's a few other things to consider at 1:1 pixel peeping one of these is a K-3 and one is a D750.

First look at web size, the image has been reduced so much, about 5:1 any possible effect from diffraction on either image is pretty much invisible. You can't tell which is which.



Pixel peeping you can see a very small difference. Now that very small difference shown at a size of 65x44, is the diffraction difference you are discussing. And to magnify it, you'd have to go over that size, pretty much a non-issue don't you think?


To see the whole image at that size, and to see that difference, you'd have to print 65 inches by 44 inches, and there is still no guarantee that the printer would produce different prints, it would depend on how accurate the printer was it reproducing minute differences in detail.

So this is the critical point of reference, at what point in a current camera system does any possible difference in diffraction become visible to the point it would negatively affect an image. And until you know that, you don't know anything practical.

There is a constant war of words, between those, who think they know something because they've read some amateur physicist , and those who spend time actually analyzing images. The question you should be trying to answer is "how is it possible that you can compare an image from a k-3 and an image from a 6D or D610, or even D750 without seeing any difference in IQ?" Why does the 1.5 magnification not make a difference? When you understand that, then you understand the correct way to apply optical physics to camera systems.

IN this case, the answer is, you are not enlarging diffraction with a K-3 until you go over 65 inches by 44 inches. Up until that point, say if you reduce the image to 4000 x 3000, you are actually doing the opposite. You are reducing the size of the image, and making the images more and more similar. That tiny bit of extra clarity in the D750 image, gets reduced, until it becomes visually imperceptible. That is what the images tell you, that your quoted source doesn't.

I know what comes next. Spin doctors come on and attack the images, Imaging resources who provide the images, the cameras used, the methodology of the test, the lenses used and my mother's heritage, so that they can remain in denial. I don't know how folks get so attached to these ideologies but they do. But, from my perspective, there is simply no excuse for it.

Look at a couple images, it's critical for you to understand what you are talking about. Looking at good comparative images and providing them to your readers, is not optional. If it doesn't exist in the real world, it doesn't exist.

I totally get that a fastidious person, like Ian, looks at the two images and thinks, I have to have the D750. But most of us simply don't look at 65"x44" inch images, and see no value in paying a lot of money for a little bit of extra clarity on 96 inch prints, (where it might make a difference) because, we don't make 96 inch prints. I sell my prints at 30"x20", and no one has ever come to me and said "I'd like a larger version of that print." I live well below the cut off point where owning a D610 or D750 would even theoretically make a difference, forget about there being much possibility of a practical difference.

Norm, if I had a Pentax full frame DSLR with the same sensor tech as my K5, I would make the images you request. But then, the relationship between format, lens aperture, and diffusion is so simple, that anyone willing to think a little does not need images to confirm it.

---------- Post added 10-21-15 at 08:28 PM ----------

QuoteOriginally posted by normhead Quote
In my experience ƒ22 is the limit of usefulness for APS-c while ƒ32 is the limit for FF

This agrees with what I have been writing and you have been arguing against! Full frame diffraction limiting happens at about one stop smaller aperture than on APS-C. Have you lost track of the discussion?
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