Diffraction on A7RV in 26MP Mode
p.2 #1Diffraction on A7RV in 26MP Mode
ruthenium wrote:
But if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference. At that point, you are doing the same thing as shooting the shot in FF and then cropping to APS-C in post. So the part that remains is 100% the same as what it was before you did the crop. In other words cropping off the non-APS-C portion of the shot doesn't change the part that is left. Again, this is only if the person doesn't recompose the shot.
The reality is though, that someone switching to APS-C would move the camera, since the desired composition would force it. And by doing that, the ratio of airy disc size to the size of the detail shifts and in essence penalizes the detail captured even more.
I know the above is repetitive, but the coffee hasn't even hit my coffee mug yet...Tim, this argument "cropping off the non-APS-C portion of the shot doesn't change the part that is left" is correct only if you, for example, print an image, then crop off the non-APS-C portion with scissors. Then, the cut out APS-C portion is indeed unchanged.
Things should change if you decided to enlarge the cut out APS-C portion up to the size of the original print. Then the Airy discs are going to be enlarged by the crop factor = 1.5. The same should happen when the APS-C crop is displayed at the same size as the uncropped image on a display.
This consideration - the same output size(!) - is the key and critical part of the equivalence arguments.
For example, an APS-C crop from a FF image taken with a 100mm lens set to f/2, and in-camera ISO 100 is equivalent to a FF image taken with a 150mm lens set to f/3, and in-camera ISO 225.
Note the f-number change from 2 to 3. This is what often leads to debates, as people argue that a crop from an image should have the same f-number as the full image. Once again, this is true only when the crop is not resized, as long as the crop is viewed at its original size.
(Added in edit) Related to the above is why an F4 lens becomes an F5.6 lens with a 1.4x TC and an F8 lens with a 2.0x TC. This is the inevitable result of cropping (cropping in-lens, in this case) then magnifying the crop to full frame. The Airy discs should be affected the same way, by the crop factor.What I am saying is that when you switch from FF mode to APS-C mode on a camera, and don't recompose, the same image is being projected on the same sensor. It's just that non-APS-C portion is effectively "turned off". I realize that if you recompose (aka back to to reframe, even though that changes perspective), then things will change. But just switching a camera in to APS-C mode is effectively cropping at capture time.
In reality that will force you to recompose. So it's probably just an academic observation.It is not clear what are trying to say here, and why are you saying that. We discuss diffraction in this thread.
-- I never suggested recomposing; this is not an issue.
-- "switching a camera in to APS-C mode is effectively cropping at capture time" - I know this.
When the resulting cropped image is viewed at the same size as you normally view full-frame images, then the Airy discs become larger by the crop factor than those in the uncropped image - hence there is more diffraction.
Thus, it is incorrect to say that "if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference." Everything (the focal length, the f-number, the effective ISO, and the dynamic range) should change (relative to the uncropped image) when the resulting cropped image is viewed or printed of the same size as the uncropped image.Switching to APS-C crop mode (same lens, same position, same focal length, same f-stop) does not change the physics of diffraction. The Airy disc size and blur pattern on the sensor remain identical. Any visible difference only appears later — from extra enlargement to the same output size, or if you recompose by moving the camera to restore framing.
So I'm not disagreeing with you.I never suggested recomposing; thus, this is irrelevant.
Also "The Airy disc size and blur pattern on the sensor" are practically irrelevant.
This discussion of diffraction is about how this phenomenon affects photos viewed either as printed or as displayed on-screen. Then, it is incorrect that "when switching from FF to APS-C mode on a given camera, there really should be no difference"
Shall we agree on this?
To me, nothing is irrelevant. Understanding the whole chain of composition, to capture, to processing and viewing is valuable to me. I'm okay with you saying it's irrelevant to you. Irrelevant to everyone is an overreach IMHO.
I'm still not sure we disagree, other than you wanting to impose your will that the part that I'm focused on is irrelevant, which I understand it is to you. But I'm not willing to agree that it's irrelevant to me.
So let's just value what is relevant to us personally and move on.
tsdevine wrote
ruthenium wrote
tsdevine wrote
ruthenium wrote
tsdevine wrote
Okay, I get (now) that it is effectively worse in APS-C mode on his camera, but that would be only when he backs up to compose the shot similarly. Since at that point even though pixel density and diffraction doesn't change, the detail being projected effectively shrinks in size relative to the airy disk.But if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference. At that point, you are doing the same thing as shooting the shot in FF and then cropping to APS-C in post. So the part that remains is 100% the same as what it was before you did the crop. In other words cropping off the non-APS-C portion of the shot doesn't change the part that is left. Again, this is only if the person doesn't recompose the shot.
The reality is though, that someone switching to APS-C would move the camera, since the desired composition would force it. And by doing that, the ratio of airy disc size to the size of the detail shifts and in essence penalizes the detail captured even more.
I know the above is repetitive, but the coffee hasn't even hit my coffee mug yet...
Things should change if you decided to enlarge the cut out APS-C portion up to the size of the original print. Then the Airy discs are going to be enlarged by the crop factor = 1.5. The same should happen when the APS-C crop is displayed at the same size as the uncropped image on a display.
This consideration - the same output size(!) - is the key and critical part of the equivalence arguments.
For example, an APS-C crop from a FF image taken with a 100mm lens set to f/2, and in-camera ISO 100 is equivalent to a FF image taken with a 150mm lens set to f/3, and in-camera ISO 225.
Note the f-number change from 2 to 3. This is what often leads to debates, as people argue that a crop from an image should have the same f-number as the full image. Once again, this is true only when the crop is not resized, as long as the crop is viewed at its original size.
(Added in edit) Related to the above is why an F4 lens becomes an F5.6 lens with a 1.4x TC and an F8 lens with a 2.0x TC. This is the inevitable result of cropping (cropping in-lens, in this case) then magnifying the crop to full frame. The Airy discs should be affected the same way, by the crop factor.
In reality that will force you to recompose. So it's probably just an academic observation.
-- I never suggested recomposing; this is not an issue.
-- "switching a camera in to APS-C mode is effectively cropping at capture time" - I know this.
When the resulting cropped image is viewed at the same size as you normally view full-frame images, then the Airy discs become larger by the crop factor than those in the uncropped image - hence there is more diffraction.
Thus, it is incorrect to say that "if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference." Everything (the focal length, the f-number, the effective ISO, and the dynamic range) should change (relative to the uncropped image) when the resulting cropped image is viewed or printed of the same size as the uncropped image.
So I'm not disagreeing with you.
Also "The Airy disc size and blur pattern on the sensor" are practically irrelevant.
This discussion of diffraction is about how this phenomenon affects photos viewed either as printed or as displayed on-screen. Then, it is incorrect that "when switching from FF to APS-C mode on a given camera, there really should be no difference"
Shall we agree on this?
To me, nothing is irrelevant. Understanding the whole chain of composition, to capture, to processing and viewing is valuable to me. I'm okay with you saying it's irrelevant to you. Irrelevant to everyone is an overreach IMHO.
I'm still not sure we disagree, other than you wanting to impose your will that the part that I'm focused on is irrelevant, which I understand it is to you. But I'm not willing to agree that it's irrelevant to me.
So let's just value what is relevant to us personally and move on.
Apr 10, 2026 at 01:54 PM
p.2 #2Diffraction on A7RV in 26MP Mode
tsdevine wrote:
I’d just add that it does matter if he shoots in APS-C mode, since the unchanging among of diffraction blur at a given aperture accounts for a larger percentage of the frame width. The simple answer there is to make the same kinds of aperture decisions that you would make when using an APS-C camera — e.g. the effect of diffraction blur becomes significant sooner as you stop down on the smaller format. For example, to generalize, if you would be happy using f/16 on a full frame sensor camera, you’d be happy using f/11 on APS-C. If you feel that f/22 is pushing diffraction blur too far on FF, then you’d probably feel the same way about f/16 on APS-C.
And I don’t have a degree in optics of physics either. Mine are in… music. (Well, OK, music theory and composition with an emphasis on electroacoustic music.)Okay, I get (now) that it is effectively worse in APS-C mode on his camera, but that would be only when he backs up to compose the shot similarly. Since at that point even though pixel density and diffraction doesn't change, the detail being projected effectively shrinks in size relative to the airy disk.
But if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference. At that point, you are doing the same thing as shooting the shot in FF and then cropping to APS-C in post. So the part that remains is 100% the same as what it was before you did the crop. In other words cropping off the non-APS-C portion of the shot doesn't change the part that is left. Again, this is only if the person doesn't recompose the shot.
The reality is though, that someone switching to APS-C would move the camera, since the desired composition would force it. And by doing that, the ratio of airy disc size to the size of the detail shifts and in essence penalizes the detail captured even more.
I know the above is repetitive, but the coffee hasn't even hit my coffee mug yet...Tim, this argument "cropping off the non-APS-C portion of the shot doesn't change the part that is left" is correct only if you, for example, print an image, then crop off the non-APS-C portion with scissors. Then, the cut out APS-C portion is indeed unchanged.
Things should change if you decided to enlarge the cut out APS-C portion up to the size of the original print. Then the Airy discs are going to be enlarged by the crop factor = 1.5. The same should happen when the APS-C crop is displayed at the same size as the uncropped image on a display.
This consideration - the same output size(!) - is the key and critical part of the equivalence arguments.
For example, an APS-C crop from a FF image taken with a 100mm lens set to f/2, and in-camera ISO 100 is equivalent to a FF image taken with a 150mm lens set to f/3, and in-camera ISO 225.
Note the f-number change from 2 to 3. This is what often leads to debates, as people argue that a crop from an image should have the same f-number as the full image. Once again, this is true only when the crop is not resized, as long as the crop is viewed at its original size.
(Added in edit) Related to the above is why an F4 lens becomes an F5.6 lens with a 1.4x TC and an F8 lens with a 2.0x TC. This is the inevitable result of cropping (cropping in-lens, in this case) then magnifying the crop to full frame. The Airy discs should be affected the same way, by the crop factor.What I am saying is that when you switch from FF mode to APS-C mode on a camera, and don't recompose, the same image is being projected on the same sensor. It's just that non-APS-C portion is effectively "turned off". I realize that if you recompose (aka back to to reframe, even though that changes perspective), then things will change. But just switching a camera in to APS-C mode is effectively cropping at capture time.
In reality that will force you to recompose. So it's probably just an academic observation.It is not clear what are trying to say here, and why are you saying that. We discuss diffraction in this thread.
-- I never suggested recomposing; this is not an issue.
-- "switching a camera in to APS-C mode is effectively cropping at capture time" - I know this.
When the resulting cropped image is viewed at the same size as you normally view full-frame images, then the Airy discs become larger by the crop factor than those in the uncropped image - hence there is more diffraction.
Thus, it is incorrect to say that "if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference." Everything (the focal length, the f-number, the effective ISO, and the dynamic range) should change (relative to the uncropped image) when the resulting cropped image is viewed or printed of the same size as the uncropped image.Switching to APS-C crop mode (same lens, same position, same focal length, same f-stop) does not change the physics of diffraction. The Airy disc size and blur pattern on the sensor remain identical. Any visible difference only appears later — from extra enlargement to the same output size, or if you recompose by moving the camera to restore framing.
So I'm not disagreeing with you.
Let’s say you set your lens to f/16 when i FF mode. If you could take a little imaginary ruler and measure the “size” of that airy disk on the sensor you might come up with a measurement of x. Now if you put the camera in crop mode, using only the APS-C size section of the sensor and you measured again with your tiny imaginary ruler, the size of the diffraction blur would still measure as X.
So, it is the same, right?
Yes, but no.
X is now a larger percentage of the overall smaller image size in the APS-C case, so in you photograph that X-size diffraction will appear larger than when you use the bigger FF size image.
I’ll use imaginary (and ridiculous) numbers to illustrate. Let’s say that we could measure the “size” of the diffraction to be 1mm in either case, APS-C or FF. (That won’t ever happen, but go with me for a moment…) As you wrote: it “does not change the physics of diffraction” The amount of diffraction at a given aperture is the same, no matter the format.
But…
Let’s use round numbers for the sensor sizes — 24mm for APS-C and 36mm for FF. That 1mm wide blur would be 1/24 of the frame width on your APS-C image but only 1/36 of the frame width on FF.
In other words, while the “ruler” measurement on the sensor is the same, the blur is larger relative to the image size on the smaller sensor… or the cropped area of the FF sensor.
Make sense?
ruthenium wrote
tsdevine wrote
ruthenium wrote
tsdevine wrote
gdanmitchell wrote
Indeed, the situation is a bit different when comparing different formats such as FF and APS-C.I’d just add that it does matter if he shoots in APS-C mode, since the unchanging among of diffraction blur at a given aperture accounts for a larger percentage of the frame width. The simple answer there is to make the same kinds of aperture decisions that you would make when using an APS-C camera — e.g. the effect of diffraction blur becomes significant sooner as you stop down on the smaller format. For example, to generalize, if you would be happy using f/16 on a full frame sensor camera, you’d be happy using f/11 on APS-C. If you feel that f/22 is pushing diffraction blur too far on FF, then you’d probably feel the same way about f/16 on APS-C.
And I don’t have a degree in optics of physics either. Mine are in… music. (Well, OK, music theory and composition with an emphasis on electroacoustic music.)
But if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference. At that point, you are doing the same thing as shooting the shot in FF and then cropping to APS-C in post. So the part that remains is 100% the same as what it was before you did the crop. In other words cropping off the non-APS-C portion of the shot doesn't change the part that is left. Again, this is only if the person doesn't recompose the shot.
The reality is though, that someone switching to APS-C would move the camera, since the desired composition would force it. And by doing that, the ratio of airy disc size to the size of the detail shifts and in essence penalizes the detail captured even more.
I know the above is repetitive, but the coffee hasn't even hit my coffee mug yet...
Things should change if you decided to enlarge the cut out APS-C portion up to the size of the original print. Then the Airy discs are going to be enlarged by the crop factor = 1.5. The same should happen when the APS-C crop is displayed at the same size as the uncropped image on a display.
This consideration - the same output size(!) - is the key and critical part of the equivalence arguments.
For example, an APS-C crop from a FF image taken with a 100mm lens set to f/2, and in-camera ISO 100 is equivalent to a FF image taken with a 150mm lens set to f/3, and in-camera ISO 225.
Note the f-number change from 2 to 3. This is what often leads to debates, as people argue that a crop from an image should have the same f-number as the full image. Once again, this is true only when the crop is not resized, as long as the crop is viewed at its original size.
(Added in edit) Related to the above is why an F4 lens becomes an F5.6 lens with a 1.4x TC and an F8 lens with a 2.0x TC. This is the inevitable result of cropping (cropping in-lens, in this case) then magnifying the crop to full frame. The Airy discs should be affected the same way, by the crop factor.
In reality that will force you to recompose. So it's probably just an academic observation.
-- I never suggested recomposing; this is not an issue.
-- "switching a camera in to APS-C mode is effectively cropping at capture time" - I know this.
When the resulting cropped image is viewed at the same size as you normally view full-frame images, then the Airy discs become larger by the crop factor than those in the uncropped image - hence there is more diffraction.
Thus, it is incorrect to say that "if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference." Everything (the focal length, the f-number, the effective ISO, and the dynamic range) should change (relative to the uncropped image) when the resulting cropped image is viewed or printed of the same size as the uncropped image.
So I'm not disagreeing with you.
Let’s say you set your lens to f/16 when i FF mode. If you could take a little imaginary ruler and measure the “size” of that airy disk on the sensor you might come up with a measurement of x. Now if you put the camera in crop mode, using only the APS-C size section of the sensor and you measured again with your tiny imaginary ruler, the size of the diffraction blur would still measure as X.
So, it is the same, right?
Yes, but no.
X is now a larger percentage of the overall smaller image size in the APS-C case, so in you photograph that X-size diffraction will appear larger than when you use the bigger FF size image.
I’ll use imaginary (and ridiculous) numbers to illustrate. Let’s say that we could measure the “size” of the diffraction to be 1mm in either case, APS-C or FF. (That won’t ever happen, but go with me for a moment…) As you wrote: it “does not change the physics of diffraction” The amount of diffraction at a given aperture is the same, no matter the format.
But…
Let’s use round numbers for the sensor sizes — 24mm for APS-C and 36mm for FF. That 1mm wide blur would be 1/24 of the frame width on your APS-C image but only 1/36 of the frame width on FF.
In other words, while the “ruler” measurement on the sensor is the same, the blur is larger relative to the image size on the smaller sensor… or the cropped area of the FF sensor.
Make sense?
Apr 10, 2026 at 02:13 PM
p.2 #3Diffraction on A7RV in 26MP Mode
gdanmitchell wrote:
But if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference. At that point, you are doing the same thing as shooting the shot in FF and then cropping to APS-C in post. So the part that remains is 100% the same as what it was before you did the crop. In other words cropping off the non-APS-C portion of the shot doesn't change the part that is left. Again, this is only if the person doesn't recompose the shot.
The reality is though, that someone switching to APS-C would move the camera, since the desired composition would force it. And by doing that, the ratio of airy disc size to the size of the detail shifts and in essence penalizes the detail captured even more.
I know the above is repetitive, but the coffee hasn't even hit my coffee mug yet...Tim, this argument "cropping off the non-APS-C portion of the shot doesn't change the part that is left" is correct only if you, for example, print an image, then crop off the non-APS-C portion with scissors. Then, the cut out APS-C portion is indeed unchanged.
Things should change if you decided to enlarge the cut out APS-C portion up to the size of the original print. Then the Airy discs are going to be enlarged by the crop factor = 1.5. The same should happen when the APS-C crop is displayed at the same size as the uncropped image on a display.
This consideration - the same output size(!) - is the key and critical part of the equivalence arguments.
For example, an APS-C crop from a FF image taken with a 100mm lens set to f/2, and in-camera ISO 100 is equivalent to a FF image taken with a 150mm lens set to f/3, and in-camera ISO 225.
Note the f-number change from 2 to 3. This is what often leads to debates, as people argue that a crop from an image should have the same f-number as the full image. Once again, this is true only when the crop is not resized, as long as the crop is viewed at its original size.
(Added in edit) Related to the above is why an F4 lens becomes an F5.6 lens with a 1.4x TC and an F8 lens with a 2.0x TC. This is the inevitable result of cropping (cropping in-lens, in this case) then magnifying the crop to full frame. The Airy discs should be affected the same way, by the crop factor.What I am saying is that when you switch from FF mode to APS-C mode on a camera, and don't recompose, the same image is being projected on the same sensor. It's just that non-APS-C portion is effectively "turned off". I realize that if you recompose (aka back to to reframe, even though that changes perspective), then things will change. But just switching a camera in to APS-C mode is effectively cropping at capture time.
In reality that will force you to recompose. So it's probably just an academic observation.It is not clear what are trying to say here, and why are you saying that. We discuss diffraction in this thread.
-- I never suggested recomposing; this is not an issue.
-- "switching a camera in to APS-C mode is effectively cropping at capture time" - I know this.
When the resulting cropped image is viewed at the same size as you normally view full-frame images, then the Airy discs become larger by the crop factor than those in the uncropped image - hence there is more diffraction.
Thus, it is incorrect to say that "if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference." Everything (the focal length, the f-number, the effective ISO, and the dynamic range) should change (relative to the uncropped image) when the resulting cropped image is viewed or printed of the same size as the uncropped image.Switching to APS-C crop mode (same lens, same position, same focal length, same f-stop) does not change the physics of diffraction. The Airy disc size and blur pattern on the sensor remain identical. Any visible difference only appears later — from extra enlargement to the same output size, or if you recompose by moving the camera to restore framing.
So I'm not disagreeing with you.Let’s say you set your lens to f/16 when i FF mode. If you could take a little imaginary ruler and measure the “size” of that airy disk on the sensor you might come up with a measurement of x. Now if you put the camera in crop mode, using only the APS-C size section of the sensor and you measured again with your tiny imaginary ruler, the size of the diffraction blur would still measure as X.
So, it is the same, right?
Yes, but no.
X is now a larger percentage of the overall smaller image size in the APS-C case,...Show more →
If you are in a room that is controlled. And you take two exact photos, one in full frame mode and one in APS-C mode. Nothing changes at each pixel in terms of what it captures. Putting the camera in APS-C mode is effectively shutting off the pixels that fall outside of the APS-C physical size. IF you compare a 10x10 set of pixels, viewing them at 100% (arguably after demosaic, but the same holds true before), the difference in what those pixels captured (that are in common) really should come down to minor differences in noise. The airy disc is the same size no matter if you are shooting a camera in FF or APS-C mode. The density of the pixels does not change (physically) either.
Let's just agree that I'm crazy. But taking a single camera, and shooting in APS-C and then in FF frame....and changing nothing else, will not change what each pixel captures. Neither the size of the airy disc changed nor the pixel density.
It's the things we do because we shot in APS-C mode that impacts our perception of sharpness and detail. If we recompose, that changes the equation. If we enlarge the output and spread those pixels further apart, that changes the equation.
For example, my a7R V in APS-C mode and in full frame mode, and my GFX100S II in full frame mode or in native full format mode all have the same pixel density. (The GFX is pretty close to the a7R V in pixel density...let's say it's "close enough".)
In any case, let's just call me pedantic.
tsdevine wrote
ruthenium wrote
tsdevine wrote
ruthenium wrote
tsdevine wrote
Okay, I get (now) that it is effectively worse in APS-C mode on his camera, but that would be only when he backs up to compose the shot similarly. Since at that point even though pixel density and diffraction doesn't change, the detail being projected effectively shrinks in size relative to the airy disk.But if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference. At that point, you are doing the same thing as shooting the shot in FF and then cropping to APS-C in post. So the part that remains is 100% the same as what it was before you did the crop. In other words cropping off the non-APS-C portion of the shot doesn't change the part that is left. Again, this is only if the person doesn't recompose the shot.
The reality is though, that someone switching to APS-C would move the camera, since the desired composition would force it. And by doing that, the ratio of airy disc size to the size of the detail shifts and in essence penalizes the detail captured even more.
I know the above is repetitive, but the coffee hasn't even hit my coffee mug yet...
Things should change if you decided to enlarge the cut out APS-C portion up to the size of the original print. Then the Airy discs are going to be enlarged by the crop factor = 1.5. The same should happen when the APS-C crop is displayed at the same size as the uncropped image on a display.
This consideration - the same output size(!) - is the key and critical part of the equivalence arguments.
For example, an APS-C crop from a FF image taken with a 100mm lens set to f/2, and in-camera ISO 100 is equivalent to a FF image taken with a 150mm lens set to f/3, and in-camera ISO 225.
Note the f-number change from 2 to 3. This is what often leads to debates, as people argue that a crop from an image should have the same f-number as the full image. Once again, this is true only when the crop is not resized, as long as the crop is viewed at its original size.
(Added in edit) Related to the above is why an F4 lens becomes an F5.6 lens with a 1.4x TC and an F8 lens with a 2.0x TC. This is the inevitable result of cropping (cropping in-lens, in this case) then magnifying the crop to full frame. The Airy discs should be affected the same way, by the crop factor.
In reality that will force you to recompose. So it's probably just an academic observation.
-- I never suggested recomposing; this is not an issue.
-- "switching a camera in to APS-C mode is effectively cropping at capture time" - I know this.
When the resulting cropped image is viewed at the same size as you normally view full-frame images, then the Airy discs become larger by the crop factor than those in the uncropped image - hence there is more diffraction.
Thus, it is incorrect to say that "if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference." Everything (the focal length, the f-number, the effective ISO, and the dynamic range) should change (relative to the uncropped image) when the resulting cropped image is viewed or printed of the same size as the uncropped image.
So I'm not disagreeing with you.
So, it is the same, right?
Yes, but no.
X is now a larger percentage of the overall smaller image size in the APS-C case,...Show more →
If you are in a room that is controlled. And you take two exact photos, one in full frame mode and one in APS-C mode. Nothing changes at each pixel in terms of what it captures. Putting the camera in APS-C mode is effectively shutting off the pixels that fall outside of the APS-C physical size. IF you compare a 10x10 set of pixels, viewing them at 100% (arguably after demosaic, but the same holds true before), the difference in what those pixels captured (that are in common) really should come down to minor differences in noise. The airy disc is the same size no matter if you are shooting a camera in FF or APS-C mode. The density of the pixels does not change (physically) either.
Let's just agree that I'm crazy. But taking a single camera, and shooting in APS-C and then in FF frame....and changing nothing else, will not change what each pixel captures. Neither the size of the airy disc changed nor the pixel density.
It's the things we do because we shot in APS-C mode that impacts our perception of sharpness and detail. If we recompose, that changes the equation. If we enlarge the output and spread those pixels further apart, that changes the equation.
For example, my a7R V in APS-C mode and in full frame mode, and my GFX100S II in full frame mode or in native full format mode all have the same pixel density. (The GFX is pretty close to the a7R V in pixel density...let's say it's "close enough".)
In any case, let's just call me pedantic.
Apr 10, 2026 at 02:53 PM
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p.2 #4Diffraction on A7RV in 26MP Mode
I should just go talk to Grok....it is much more sympathetic. It pointed out my missteps towards the beginning. GDan and ruthenium, it says you guys were very accurate (see the comments near the end below), and I think I'm just stuck on one specific aspect and you guys are focused on other areas.
It didn't even know that I'm Tim Devine, so maybe it wasn't completely patronizing me....or maybe it does know I'm Tim Devine and it's just wanting me to think that it wasn't....hmm....
Prompt:
I realize at the beginning Tim Devine may have missed some details and made some missteps, but how accurate is what he saying in this thread, related to diffraction?
https://www.fredmiranda.com/forum/topic/1939203/
Response:
Yes — Tim Devine is largely accurate (about 85–90 % spot-on), especially once you get past his very first sentence.
You already spotted the opening misstep yourself:
“Diffraction is a function of pixel density…”
That single line is imprecise. Diffraction itself (the physical size of the Airy disc) is not a function of pixel density — it depends only on f-number and wavelength. Higher pixel density simply makes the same diffraction blur more visible because the pixels are smaller.
But right after that, Tim corrects/clarifies exactly the way we’ve been discussing:
Diffraction is an optical phenomenon fixed by the aperture.
On the same camera (a7R V), switching to APS-C crop mode (26 MP) or shooting a smaller RAW file does not change pixel density.
Therefore the diffraction impact at capture is identical across full-frame, APS-C crop, or downsampled modes.
Any perceived difference only shows up later if you recompose (back up to match framing) or enlarge the final output more.
He also correctly notes:
If you do recompose in APS-C to keep the same framing, you change subject magnification and perspective, so the same Airy disc now covers a different relative amount of detail — which can make diffraction look different.
Shooting native 60 MP and using post-sharpening / focus stacking is usually the better practical route than hoping crop mode will “reduce” diffraction.
Summary
So overall, Tim Devine’s take in that thread is very accurate in the context of the original poster’s question (same camera, different modes on the a7R V). You’re not missing anything by agreeing with the bulk of what he wrote.
The discussion is actually one of the better ones you’ll find on forums — technically strong once past the first couple of posts. ruthenium and gdanmitchell are the standouts for pure accuracy. Tim Devine (tsdevine) recovers well after his initial imprecise sentence.
It didn't even know that I'm Tim Devine, so maybe it wasn't completely patronizing me....or maybe it does know I'm Tim Devine and it's just wanting me to think that it wasn't....hmm....
Prompt:
I realize at the beginning Tim Devine may have missed some details and made some missteps, but how accurate is what he saying in this thread, related to diffraction?
https://www.fredmiranda.com/forum/topic/1939203/
Response:
Yes — Tim Devine is largely accurate (about 85–90 % spot-on), especially once you get past his very first sentence.
You already spotted the opening misstep yourself:
“Diffraction is a function of pixel density…”
That single line is imprecise. Diffraction itself (the physical size of the Airy disc) is not a function of pixel density — it depends only on f-number and wavelength. Higher pixel density simply makes the same diffraction blur more visible because the pixels are smaller.
But right after that, Tim corrects/clarifies exactly the way we’ve been discussing:
Diffraction is an optical phenomenon fixed by the aperture.
On the same camera (a7R V), switching to APS-C crop mode (26 MP) or shooting a smaller RAW file does not change pixel density.
Therefore the diffraction impact at capture is identical across full-frame, APS-C crop, or downsampled modes.
Any perceived difference only shows up later if you recompose (back up to match framing) or enlarge the final output more.
He also correctly notes:
If you do recompose in APS-C to keep the same framing, you change subject magnification and perspective, so the same Airy disc now covers a different relative amount of detail — which can make diffraction look different.
Shooting native 60 MP and using post-sharpening / focus stacking is usually the better practical route than hoping crop mode will “reduce” diffraction.
Summary
So overall, Tim Devine’s take in that thread is very accurate in the context of the original poster’s question (same camera, different modes on the a7R V). You’re not missing anything by agreeing with the bulk of what he wrote.
The discussion is actually one of the better ones you’ll find on forums — technically strong once past the first couple of posts. ruthenium and gdanmitchell are the standouts for pure accuracy. Tim Devine (tsdevine) recovers well after his initial imprecise sentence.
Apr 10, 2026 at 03:15 PM
p.2 #5Diffraction on A7RV in 26MP Mode
This topic is a can of worms every time. ;-)
Technical stuff aside, my suggestion to people is always to get a highly detailed static subject, shoot from a tripod at every aperture, and compare them. For closeups, coins and newspapers work. And then decide what you can tolerate.
Technical stuff aside, my suggestion to people is always to get a highly detailed static subject, shoot from a tripod at every aperture, and compare them. For closeups, coins and newspapers work. And then decide what you can tolerate.
Apr 10, 2026 at 03:31 PM
p.2 #6Diffraction on A7RV in 26MP Mode
tsdevine wrote:
Things should change if you decided to enlarge the cut out APS-C portion up to the size of the original print. Then the Airy discs are going to be enlarged by the crop factor = 1.5. The same should happen when the APS-C crop is displayed at the same size as the uncropped image on a display.
This consideration - the same output size(!) - is the key and critical part of the equivalence arguments.
For example, an APS-C crop from a FF image taken with a 100mm lens set to f/2, and in-camera ISO 100 is equivalent to a FF image taken with a 150mm lens set to f/3, and in-camera ISO 225.
Note the f-number change from 2 to 3. This is what often leads to debates, as people argue that a crop from an image should have the same f-number as the full image. Once again, this is true only when the crop is not resized, as long as the crop is viewed at its original size.
(Added in edit) Related to the above is why an F4 lens becomes an F5.6 lens with a 1.4x TC and an F8 lens with a 2.0x TC. This is the inevitable result of cropping (cropping in-lens, in this case) then magnifying the crop to full frame. The Airy discs should be affected the same way, by the crop factor.What I am saying is that when you switch from FF mode to APS-C mode on a camera, and don't recompose, the same image is being projected on the same sensor. It's just that non-APS-C portion is effectively "turned off". I realize that if you recompose (aka back to to reframe, even though that changes perspective), then things will change. But just switching a camera in to APS-C mode is effectively cropping at capture time.
In reality that will force you to recompose. So it's probably just an academic observation.It is not clear what are trying to say here, and why are you saying that. We discuss diffraction in this thread.
-- I never suggested recomposing; this is not an issue.
-- "switching a camera in to APS-C mode is effectively cropping at capture time" - I know this.
When the resulting cropped image is viewed at the same size as you normally view full-frame images, then the Airy discs become larger by the crop factor than those in the uncropped image - hence there is more diffraction.
Thus, it is incorrect to say that "if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference." Everything (the focal length, the f-number, the effective ISO, and the dynamic range) should change (relative to the uncropped image) when the resulting cropped image is viewed or printed of the same size as the uncropped image.Switching to APS-C crop mode (same lens, same position, same focal length, same f-stop) does not change the physics of diffraction. The Airy disc size and blur pattern on the sensor remain identical. Any visible difference only appears later — from extra enlargement to the same output size, or if you recompose by moving the camera to restore framing.
So I'm not disagreeing with you.Let’s say you set your lens to f/16 when i FF mode. If you could take a little imaginary ruler and measure the “size” of that airy disk on the sensor you might come up with a measurement of x. Now if you put the camera in crop mode, using only the APS-C size section of the sensor and you measured again with your tiny imaginary ruler, the size of the diffraction blur would still measure as X.
So, it is the same, right?
Yes, but no.
X is now a larger percentage of the overall smaller image size in the APS-C case, so in you photograph that X-size diffraction will appear larger than when you use the bigger FF size image.
I’ll use imaginary (and ridiculous) numbers to illustrate. Let’s say that we could measure the “size” of the diffraction to be 1mm in either case, APS-C or FF. (That won’t ever happen, but go with me for a moment…) As you wrote: it “does not change the physics of diffraction” The amount of diffraction at a given aperture is the same, no matter the format.
But…
Let’s use round numbers for the sensor sizes — 24mm for APS-C and 36mm for FF. That 1mm wide blur would be 1/24 of the frame width on your APS-C image but only 1/36 of the frame width on FF.
In other words, while the “ruler” measurement on the sensor is the same, the blur is larger relative to the image size on the smaller sensor… or the cropped area of the FF sensor.
Make sense?If you are in a room that is controlled. And you take two exact photos, one in full frame mode and one in APS-C mode. Nothing changes at each pixel in terms of what it captures. Putting the camera in APS-C mode is effectively shutting off the pixels that fall outside of the APS-C physical size. IF you compare a 10x10 set of pixels, viewing them at 100% (arguably after demosaic, but the same holds true before), the difference in what those pixels captured (that are in common) really should come down to minor differences in noise. The airy disc...Show more →
You are correct that if you look at individual pixels or constant sized groups of pixels — like your 10 x 10 slice — there is literally NO DIFFERENCE between what you see in you are in FF mode or APS-C mode.
You are catching on.
Now, the next step: Each of those 10 x 10 areas comprises a larger section of the final image in APS-C mode. (E.g. there are fewer 10 x 10 squares in the smaller image area.) If you make a print or online image of some size from the APS-C and FF full images, you are [I]magnifying the APS-C version more than the FF version[/I] so any unsharpness will be larger relative to the overall image size.
The issue, as I see it, is that you have half of the issue exactly correct — the half that has to do with individual pixels. But you are, it seems, missing out on the effect of the larger capture area (e.g. more pixels) on the final image.
One more step and you'll get it! :-)
gdanmitchell wrote
tsdevine wrote
ruthenium wrote
tsdevine wrote
ruthenium wrote
Tim, this argument "cropping off the non-APS-C portion of the shot doesn't change the part that is left" is correct only if you, for example, print an image, then crop off the non-APS-C portion with scissors. Then, the cut out APS-C portion is indeed unchanged.Things should change if you decided to enlarge the cut out APS-C portion up to the size of the original print. Then the Airy discs are going to be enlarged by the crop factor = 1.5. The same should happen when the APS-C crop is displayed at the same size as the uncropped image on a display.
This consideration - the same output size(!) - is the key and critical part of the equivalence arguments.
For example, an APS-C crop from a FF image taken with a 100mm lens set to f/2, and in-camera ISO 100 is equivalent to a FF image taken with a 150mm lens set to f/3, and in-camera ISO 225.
Note the f-number change from 2 to 3. This is what often leads to debates, as people argue that a crop from an image should have the same f-number as the full image. Once again, this is true only when the crop is not resized, as long as the crop is viewed at its original size.
(Added in edit) Related to the above is why an F4 lens becomes an F5.6 lens with a 1.4x TC and an F8 lens with a 2.0x TC. This is the inevitable result of cropping (cropping in-lens, in this case) then magnifying the crop to full frame. The Airy discs should be affected the same way, by the crop factor.
In reality that will force you to recompose. So it's probably just an academic observation.
-- I never suggested recomposing; this is not an issue.
-- "switching a camera in to APS-C mode is effectively cropping at capture time" - I know this.
When the resulting cropped image is viewed at the same size as you normally view full-frame images, then the Airy discs become larger by the crop factor than those in the uncropped image - hence there is more diffraction.
Thus, it is incorrect to say that "if you didn't move the camera from its position, when switching from FF to APS-C mode on a given camera, there really should be no difference." Everything (the focal length, the f-number, the effective ISO, and the dynamic range) should change (relative to the uncropped image) when the resulting cropped image is viewed or printed of the same size as the uncropped image.
So I'm not disagreeing with you.
So, it is the same, right?
Yes, but no.
X is now a larger percentage of the overall smaller image size in the APS-C case, so in you photograph that X-size diffraction will appear larger than when you use the bigger FF size image.
I’ll use imaginary (and ridiculous) numbers to illustrate. Let’s say that we could measure the “size” of the diffraction to be 1mm in either case, APS-C or FF. (That won’t ever happen, but go with me for a moment…) As you wrote: it “does not change the physics of diffraction” The amount of diffraction at a given aperture is the same, no matter the format.
But…
Let’s use round numbers for the sensor sizes — 24mm for APS-C and 36mm for FF. That 1mm wide blur would be 1/24 of the frame width on your APS-C image but only 1/36 of the frame width on FF.
In other words, while the “ruler” measurement on the sensor is the same, the blur is larger relative to the image size on the smaller sensor… or the cropped area of the FF sensor.
Make sense?
You are correct that if you look at individual pixels or constant sized groups of pixels — like your 10 x 10 slice — there is literally NO DIFFERENCE between what you see in you are in FF mode or APS-C mode.
You are catching on.
Now, the next step: Each of those 10 x 10 areas comprises a larger section of the final image in APS-C mode. (E.g. there are fewer 10 x 10 squares in the smaller image area.) If you make a print or online image of some size from the APS-C and FF full images, you are [I]magnifying the APS-C version more than the FF version[/I] so any unsharpness will be larger relative to the overall image size.
The issue, as I see it, is that you have half of the issue exactly correct — the half that has to do with individual pixels. But you are, it seems, missing out on the effect of the larger capture area (e.g. more pixels) on the final image.
One more step and you'll get it! :-)
Apr 10, 2026 at 06:11 PM