Canon Full Frame Mirrorless Talk [CR1]

[Loswr]

I am just a bit picky, since it is important to define what one is speaking about. To say an APSC image has to be magnified more compared to a FF image is not correct, if it has the same amount of pixels. The size of an output image is determined by the pixels, contrary to film. Optically speaking it boils down to the relative size of the sensor to the defined COC.

Ermm...no. As PBD says, it boils down to you being wrong. The size of an output image is determined by the size of the output image – the picture printed at a given size (e.g. 8x10" which is the standard assumption for DoF calculators, or A2, or whataver you pick) or digitally viewed at a given size (e.g. the 14" digital picture frame on my desk, which is a screen size of 12.2x6.9", or the full screen mode of the 14.4x9" display of the 17" MacBook Pro on which I'm typing this post). The pixels are irrelevant - the image will be scaled to fit the output size. The 'input size' is the physical size of the imaging medium – in the case of a digital sensor, that's approximately 36x24mm for FF and 22x15mm for Canon's APS-C. Simple math will tell you that to go from an APS-C sensor to an 8x10" print or a 14" digital frame will require a greater increase in magnification than to go from a FF sensor to an 8x10" print or 14" digital frame.

 

[LonelyBoy]

"The issue is that for a comparable constant output size a smaller sensor has to be enlarged more, therefore the smaller sensor 'on sensor' coc must be a smaller number. Ergo sensor size, as we equate the concept into actual images, does impact dof for comparative purposes."
That is the film concept. In digital you don't need to enlarge an image of an equal MP APSC or FF sensor more.
It is the relative size of the COC to the dimension of the sensor which is important. The light cone coming from an object needs to lie within the COC, to be still envisioned as a point in the final image for a certain viewing distance. In the DOF formulas the COC stays the same when cropping, but magnification m changes (1/m^2 in the formula), thereby leading to the observed changes. Mathematically the result is similar.

Don't be rediculous, that the information is digitized doesn't negate the fact that it is a digital representation of a physical optical projection onto that digital medium. The dof characteristics are identical for film and digital sensors, if they are the same size thos echarachteristics are the same, if they are different sizes they have different dof characteristics.

I am just a bit picky, since it is important to define what one is speaking about. To say an APSC image has to be magnified more compared to a FF image is not correct, if it has the same amount of pixels. The size of an output image is determined by the pixels, contrary to film. Optically speaking it boils down to the relative size of the sensor to the defined COC.

Not to pile on, but the output size of a digital image is no more determined by pixels than film was by grain. What you should be thinking of, to understand this whole process, is a system like OLAF over at LensRentals, which can evaluate a lens without a sensor. The lens projects an image onto the sensor area; the sensor samples that image at its resolution. Images do not have to be viewed at 100% zoom. A smaller area (sensor) has to be magnified more to reach an arbitrary output physical size, no matter what form that physical output is (screen, print, billboard). Specifically, an m43 image has to be magnified 3.8x more than FF, even if you compare a high-density m43 sensor and an old, original 5D. This is true no matter what the final output size is.

 

[Hflm]

I am just a bit picky, since it is important to define what one is speaking about. To say an APSC image has to be magnified more compared to a FF image is not correct, if it has the same amount of pixels. The size of an output image is determined by the pixels, contrary to film. Optically speaking it boils down to the relative size of the sensor to the defined COC.

Ermm...no. As PBD says, it boils down to you being wrong. The size of an output image is determined by the size of the output image – the picture printed at a given size (e.g. 8x10" which is the standard assumption for DoF calculators, or A2, or whataver you pick) or digitally viewed at a given size (e.g. the 14" digital picture frame on my desk, which is a screen size of 12.2x6.9", or the full screen mode of the 14.4x9" display of the 17" MacBook Pro on which I'm typing this post). The pixels are irrelevant - the image will be scaled to fit the output size. The 'input size' is the physical size of the imaging medium – in the case of a digital sensor, that's approximately 36x24mm for FF and 22x15mm for Canon's APS-C. Simple math will tell you that to go from an APS-C sensor to an 8x10" print or a 14" digital frame will require a greater increase in magnification than to go from a FF sensor to an 8x10" print or 14" digital frame.

I think we speak about the same thing just looking at it differently. I look at it at the sensor level following the light cones behind and in front of the object plane to the image plane. I compare the relative size of the COC to the sensor size or object COC to object size, as mentioned several time in my posts above. This _factor_ between COC and sensor size doesn't change when scaling the COC and sensor both to some virtual output size. It is this factor which is important, not the output size. My interpretation of what you mean with magnification is that when cropping for example, the relative size of the object COC (stays the same) to image size now changes, the factor increases. The blur is magnified and DOF decreases. So your notion that the crop image is magnified more for me is just that the relative size of the COC to image changes due to a crop or when using a crop sensor. I decouple that from the size of an image based on pixels when viewing on a monitor, maybe I expressed myself not correctly here.

See here about the magnification myth:
https://luminous-landscape.com/dslr-magnification/

 

[100]

I told you what I what talking about, light gathering, a FF sensor gathers 3.81 times as much light.

The difficulty with linear resolution is there is a difference in aspect ratio (4:3 compared to 3:2) so it’s apples to oranges. Let’s just compare megapixels: 20.1 versus 13.2 (50.3/3.81) so the E-M1 Mark II has 65% more megapixels and that’s not even close to equal. It’s about the same difference as between the original 5D and the 5D Mark II.

That is what confused me.
You said you are not talking about resolution - but pixels give resolution. More pixels = more resolution = effect on DOF.
I am not sure what effect 'light gathering' has on it. Or were you not talking about DOF at that point (most people refer to 'equivalence regards DOF but maybe you were not in this case?

More pixels = more resolution => True
more resolution = effect on DOF => False

It’s like privatebydesign says in his reply from 10:23:57 AM:
Only two things create dof after you define what is 'acceptable', the apparent magnification to you in real time of the output and the size of the aperture in the lens at capture, not the f number, the actual size.

Just check any DOF calculator if you doubt that. Compare a Nikon D700 (FF 12mp) to a Nikon D800 (FF 36mp) and you’ll see the DOF is exactly the same.

 

[Hflm]

I told you what I what talking about, light gathering, a FF sensor gathers 3.81 times as much light.

The difficulty with linear resolution is there is a difference in aspect ratio (4:3 compared to 3:2) so it’s apples to oranges. Let’s just compare megapixels: 20.1 versus 13.2 (50.3/3.81) so the E-M1 Mark II has 65% more megapixels and that’s not even close to equal. It’s about the same difference as between the original 5D and the 5D Mark II.

That is what confused me.
You said you are not talking about resolution - but pixels give resolution. More pixels = more resolution = effect on DOF.
I am not sure what effect 'light gathering' has on it. Or were you not talking about DOF at that point (most people refer to 'equivalence regards DOF but maybe you were not in this case?

More pixels = more resolution => True
more resolution = effect on DOF => False

It’s like privatebydesign says in his reply from 10:23:57 AM:
Only two things create dof after you define what is 'acceptable', the apparent magnification to you in real time of the output and the size of the aperture in the lens at capture, not the f number, the actual size.

The DOF equation shows it depends on f#, magnification (involves distance), focal length (term in the denominator, could become negligible in some cases) and COC (http://toothwalker.org/optics/dofderivation.html eq. 12).

 

[bdunbar79]

I am just a bit picky, since it is important to define what one is speaking about. To say an APSC image has to be magnified more compared to a FF image is not correct, if it has the same amount of pixels. The size of an output image is determined by the pixels, contrary to film. Optically speaking it boils down to the relative size of the sensor to the defined COC.

Ermm...no. As PBD says, it boils down to you being wrong. The size of an output image is determined by the size of the output image – the picture printed at a given size (e.g. 8x10" which is the standard assumption for DoF calculators, or A2, or whataver you pick) or digitally viewed at a given size (e.g. the 14" digital picture frame on my desk, which is a screen size of 12.2x6.9", or the full screen mode of the 14.4x9" display of the 17" MacBook Pro on which I'm typing this post). The pixels are irrelevant - the image will be scaled to fit the output size. The 'input size' is the physical size of the imaging medium – in the case of a digital sensor, that's approximately 36x24mm for FF and 22x15mm for Canon's APS-C. Simple math will tell you that to go from an APS-C sensor to an 8x10" print or a 14" digital frame will require a greater increase in magnification than to go from a FF sensor to an 8x10" print or 14" digital frame.

I think we speak about the same thing just looking at it differently. I look at it at the sensor level following the light cones behind and in front of the object plane to the image plane. I compare the relative size of the COC to the sensor size or object COC to object size, as mentioned several time in my posts above. This _factor_ between COC and sensor size doesn't change when scaling the COC and sensor both to some virtual output size. It is this factor which is important, not the output size. My interpretation of what you mean with magnification is that when cropping for example, the relative size of the object COC (stays the same) to image size now changes, the factor increases. The blur is magnified and DOF decreases. So your notion that the crop image is magnified more for me is just that the relative size of the COC to image changes due to a crop or when using a crop sensor. I decouple that from the size of an image based on pixels when viewing on a monitor, maybe I expressed myself not correctly here.

See here about the magnification myth:
https://luminous-landscape.com/dslr-magnification/

I can't take it anymore. No offense but you are really being foolish.

 

[Hflm]

I am just a bit picky, since it is important to define what one is speaking about. To say an APSC image has to be magnified more compared to a FF image is not correct, if it has the same amount of pixels. The size of an output image is determined by the pixels, contrary to film. Optically speaking it boils down to the relative size of the sensor to the defined COC.

Ermm...no. As PBD says, it boils down to you being wrong. The size of an output image is determined by the size of the output image – the picture printed at a given size (e.g. 8x10" which is the standard assumption for DoF calculators, or A2, or whataver you pick) or digitally viewed at a given size (e.g. the 14" digital picture frame on my desk, which is a screen size of 12.2x6.9", or the full screen mode of the 14.4x9" display of the 17" MacBook Pro on which I'm typing this post). The pixels are irrelevant - the image will be scaled to fit the output size. The 'input size' is the physical size of the imaging medium – in the case of a digital sensor, that's approximately 36x24mm for FF and 22x15mm for Canon's APS-C. Simple math will tell you that to go from an APS-C sensor to an 8x10" print or a 14" digital frame will require a greater increase in magnification than to go from a FF sensor to an 8x10" print or 14" digital frame.

I think we speak about the same thing just looking at it differently. I look at it at the sensor level following the light cones behind and in front of the object plane to the image plane. I compare the relative size of the COC to the sensor size or object COC to object size, as mentioned several time in my posts above. This _factor_ between COC and sensor size doesn't change when scaling the COC and sensor both to some virtual output size. It is this factor which is important, not the output size. My interpretation of what you mean with magnification is that when cropping for example, the relative size of the object COC (stays the same) to image size now changes, the factor increases. The blur is magnified and DOF decreases. So your notion that the crop image is magnified more for me is just that the relative size of the COC to image changes due to a crop or when using a crop sensor. I decouple that from the size of an image based on pixels when viewing on a monitor, maybe I expressed myself not correctly here.

See here about the magnification myth:
https://luminous-landscape.com/dslr-magnification/

I can't take it anymore. No offense but you are really being foolish.

Being rude doesn't help. Read the Zeiss document on DOF (https://www.zeiss.com/content/dam/Photography/new/pdf/en/cln_archiv/cln35_en_web_special_bokeh.pdf) or the link above on the derivation of the DOF equation, if you understand it at all (http://toothwalker.org/optics/dofderivation.html).

 

[BillB]

So. Much. Misunderstanding. Of. Optics.

;D

I have to say that at this point I am a little unclear as to what the subject is, exactly. It seems to me that at least one element of the discussion is what effect the size of the capture sensor (measured either as physical size or as the number of pixels) has on the quality of a final image of a given size.

Factors influencing final image quality can be divided in to factors present before sensor capture and factors occurring during or after sensor capture. It seems clear to me that factors present before sensor capture (lens accuity, motion blur etc.) will be magnified in proportion to the physical scaling to produce the final image. These factors are baked in at sensor capture and they are affected by the physical crop factor, rather than the number of pixels in the sensor.

I have no idea how factors occurring during and after sensor capture are influenced by the amount of physical scaling or the number of pixels. Nor do I have any idea how significant factors occurring during and after sensor capture are to the quality of the final image.

 

[100]

I told you what I what talking about, light gathering, a FF sensor gathers 3.81 times as much light.

The difficulty with linear resolution is there is a difference in aspect ratio (4:3 compared to 3:2) so it’s apples to oranges. Let’s just compare megapixels: 20.1 versus 13.2 (50.3/3.81) so the E-M1 Mark II has 65% more megapixels and that’s not even close to equal. It’s about the same difference as between the original 5D and the 5D Mark II.

That is what confused me.
You said you are not talking about resolution - but pixels give resolution. More pixels = more resolution = effect on DOF.
I am not sure what effect 'light gathering' has on it. Or were you not talking about DOF at that point (most people refer to 'equivalence regards DOF but maybe you were not in this case?

More pixels = more resolution => True
more resolution = effect on DOF => False

It’s like privatebydesign says in his reply from 10:23:57 AM:
Only two things create dof after you define what is 'acceptable', the apparent magnification to you in real time of the output and the size of the aperture in the lens at capture, not the f number, the actual size.

The DOF equation shows it depends on f#, magnification (involves distance), focal length (term in the denominator, could become negligible in some cases) and COC (http://toothwalker.org/optics/dofderivation.html eq. 12).

I’m sorry, I don’t see the point you are trying to make.

 

[privatebydesign]

I am just a bit picky, since it is important to define what one is speaking about. To say an APSC image has to be magnified more compared to a FF image is not correct, if it has the same amount of pixels. The size of an output image is determined by the pixels, contrary to film. Optically speaking it boils down to the relative size of the sensor to the defined COC.

Ermm...no. As PBD says, it boils down to you being wrong. The size of an output image is determined by the size of the output image – the picture printed at a given size (e.g. 8x10" which is the standard assumption for DoF calculators, or A2, or whataver you pick) or digitally viewed at a given size (e.g. the 14" digital picture frame on my desk, which is a screen size of 12.2x6.9", or the full screen mode of the 14.4x9" display of the 17" MacBook Pro on which I'm typing this post). The pixels are irrelevant - the image will be scaled to fit the output size. The 'input size' is the physical size of the imaging medium – in the case of a digital sensor, that's approximately 36x24mm for FF and 22x15mm for Canon's APS-C. Simple math will tell you that to go from an APS-C sensor to an 8x10" print or a 14" digital frame will require a greater increase in magnification than to go from a FF sensor to an 8x10" print or 14" digital frame.

I think we speak about the same thing just looking at it differently. I look at it at the sensor level following the light cones behind and in front of the object plane to the image plane. I compare the relative size of the COC to the sensor size or object COC to object size, as mentioned several time in my posts above. This _factor_ between COC and sensor size doesn't change when scaling the COC and sensor both to some virtual output size. It is this factor which is important, not the output size. My interpretation of what you mean with magnification is that when cropping for example, the relative size of the object COC (stays the same) to image size now changes, the factor increases. The blur is magnified and DOF decreases. So your notion that the crop image is magnified more for me is just that the relative size of the COC to image changes due to a crop or when using a crop sensor. I decouple that from the size of an image based on pixels when viewing on a monitor, maybe I expressed myself not correctly here.

See here about the magnification myth:
https://luminous-landscape.com/dslr-magnification/

I can't take it anymore. No offense but you are really being foolish.

Being rude doesn't help. Read the Zeiss document on DOF (https://www.zeiss.com/content/dam/Photography/new/pdf/en/cln_archiv/cln35_en_web_special_bokeh.pdf) or the link above on the derivation of the DOF equation, if you understand it at all (http://toothwalker.org/optics/dofderivation.html).

Read this.

http://www.josephjamesphotography.com/equivalence/

 

[unfocused]

The crop-DoF debate finally reaches CanonRumors...

You are obviously new around here. This debate has been hashed and rehashed to death before. But that isn't going to stop people from doing it once again.

Welcome to a debate over one of the most obscure and insignificant characteristics of photography.

So the question is, why does e.g. Panasonic quote the FF equivalence when talking about the focal length but not when talking about the aperture?

Well, I think the last several pages should answer that. Too confusing and too insignificant.

This is the kind of debate that has virtually no use in the real world. Whatever camera and lens combination you are using, you should compose the image for that combination. If depth of field matters to you, take that into account for the equipment you are using.

 

[Don Haines]

The crop-DoF debate finally reaches CanonRumors...

You are obviously new around here. This debate has been hashed and rehashed to death before. But that isn't going to stop people from doing it once again.

Welcome to a debate over one of the most obscure and insignificant characteristics of photography.

So the question is, why does e.g. Panasonic quote the FF equivalence when talking about the focal length but not when talking about the aperture?

Well, I think the last several pages should answer that. Too confusing and too insignificant.

This is the kind of debate that has virtually no use in the real world. Whatever camera and lens combination you are using, you should compose the image for that combination. If depth of field matters to you, take that into account for the equipment you are using.

OK! THAT'S IT!!!! THIS IS YOUR THIRD WARNING!!!!

You are using common sense on the web.... This is neither the time nor the place for it!

 

[privatebydesign]

This is the kind of debate that has virtually no use in the real world. Whatever camera and lens combination you are using, you should compose the image for that combination. If depth of field matters to you, take that into account for the equipment you are using.

I disagree, understanding how it all works is very important for some people to understand how to get what they want.

For instance if you run a combination crop and ff camera kit you instantly understand how your lens stable interacts with them and what you can use to get a look you want.

Sure for many people it is irrelevant, so what? If it helps anybody then the discussion has value. But what drives me to post in threads like this is when people give out information that is factually wrong, I try hard to correct that misinformation for the good of all.

 

[Orangutan]

If all you change is the sensor size, then obviously you are changing the framing. In that case, depth of field is shallower with the smaller sensor because the circle of confusion is smaller.

Please explain this: I can convert a FF to a smaller sensor by putting tape over the outer edges. Are you saying that this would affect the circle of confusion, and therefore the DoF? If so, I've got some reading to do.

That's exactly what I'm saying. In practical terms, sensor size (i.e. the physical area used to capture an image) determines circle of confusion.

In technical terms, it's more complicated than that because CoC is really about 'acceptable blur' which is also a function of output size, viewing distance, and the visual acuity of the viewer. But when talking about depth of field, we hold all of those at a constant value (fixed and arbitrary), so the only thing that determines CoC is the physical size of the image on the capture media (the sensor), because that determines how much you have to enlarge it to achieve the chosen (fixed) output size.

I think my confusion here is that we're holding different things constant. You're starting with the presumption that the output size must stay the same between FF and crop, while I'm assuming that the objects in the respected outputs stay the same size. E.g. if the central subject is a tree 10cm tall in the FF print, it's also 10cm tall in the output of the crop print. I don't see that either of us is objectively correct, just different assumptions. As you describe the test, it looks like a series of changes to me, and the reverse to you; e.g.

Framing: Keep the distance to subject equal, then framing changes. (and reverse)

Print: Keep the overall print size equal, then object size changes. (and reverse)

I think the point is that there is no such thing as "all else kept equal," we just need to be explicit about our conditions. The one point on which I'll hold on to a small piece of pride is that Don's statement was, ultimately, about the behavior of the lens. He was not talking about the final print, but about what happens to light as it passes through the lens. Changing subject distance invalidates that comparison.

 

[privatebydesign]

If all you change is the sensor size, then obviously you are changing the framing. In that case, depth of field is shallower with the smaller sensor because the circle of confusion is smaller.

Please explain this: I can convert a FF to a smaller sensor by putting tape over the outer edges. Are you saying that this would affect the circle of confusion, and therefore the DoF? If so, I've got some reading to do.

That's exactly what I'm saying. In practical terms, sensor size (i.e. the physical area used to capture an image) determines circle of confusion.

In technical terms, it's more complicated than that because CoC is really about 'acceptable blur' which is also a function of output size, viewing distance, and the visual acuity of the viewer. But when talking about depth of field, we hold all of those at a constant value (fixed and arbitrary), so the only thing that determines CoC is the physical size of the image on the capture media (the sensor), because that determines how much you have to enlarge it to achieve the chosen (fixed) output size.

I think my confusion here is that we're holding different things constant. You're starting with the presumption that the output size must stay the same between FF and crop, while I'm assuming that the objects in the respected outputs stay the same size. E.g. if the central subject is a tree 10cm tall in the FF print, it's also 10cm tall in the output of the crop print. I don't see that either of us is objectively correct, just different assumptions. As you describe the test, it looks like a series of changes to me, and the reverse to you; e.g.

Framing: Keep the distance to subject equal, then framing changes. (and reverse)

Print: Keep the overall print size equal, then object size changes. (and reverse)

I think the point is that there is no such thing as "all else kept equal," we just need to be explicit about our conditions. The one point on which I'll hold on to a small piece of pride is that Don's statement was, ultimately, about the behavior of the lens. He was not talking about the final print, but about what happens to light as it passes through the lens. Changing subject distance invalidates that comparison.

Please just read this.

http://www.josephjamesphotography.com/equivalence/

 

[Orangutan]

If all you change is the sensor size, then obviously you are changing the framing. In that case, depth of field is shallower with the smaller sensor because the circle of confusion is smaller.

Please explain this: I can convert a FF to a smaller sensor by putting tape over the outer edges. Are you saying that this would affect the circle of confusion, and therefore the DoF? If so, I've got some reading to do.

That's exactly what I'm saying. In practical terms, sensor size (i.e. the physical area used to capture an image) determines circle of confusion.

In technical terms, it's more complicated than that because CoC is really about 'acceptable blur' which is also a function of output size, viewing distance, and the visual acuity of the viewer. But when talking about depth of field, we hold all of those at a constant value (fixed and arbitrary), so the only thing that determines CoC is the physical size of the image on the capture media (the sensor), because that determines how much you have to enlarge it to achieve the chosen (fixed) output size.

I think my confusion here is that we're holding different things constant. You're starting with the presumption that the output size must stay the same between FF and crop, while I'm assuming that the objects in the respected outputs stay the same size. E.g. if the central subject is a tree 10cm tall in the FF print, it's also 10cm tall in the output of the crop print. I don't see that either of us is objectively correct, just different assumptions. As you describe the test, it looks like a series of changes to me, and the reverse to you; e.g.

Framing: Keep the distance to subject equal, then framing changes. (and reverse)

Print: Keep the overall print size equal, then object size changes. (and reverse)

I think the point is that there is no such thing as "all else kept equal," we just need to be explicit about our conditions. The one point on which I'll hold on to a small piece of pride is that Don's statement was, ultimately, about the behavior of the lens. He was not talking about the final print, but about what happens to light as it passes through the lens. Changing subject distance invalidates that comparison.

Please just read this.

http://www.josephjamesphotography.com/equivalence/

Sure, when I have time. But remember that this was never a question about equivalence, but about the behavior of the lens. This is the key statement from Don's original post. It is correct.

Lenses do not magically change properties when swapped onto different bodies. The optics do not change. The photon entering the lens does not know what sensor is at the far end of the lens and can not change it's path based on that.....

Somewhere the thread was hijacked to become a discussion of CoC.

 

[Loswr]

I think my confusion here is that we're holding different things constant. You're starting with the presumption that the output size must stay the same between FF and crop, while I'm assuming that the objects in the respected outputs stay the same size.

Sure, you can vary whatever you want. But when discussing DoF, in particular when calculating it, by convention we hold output size, viewing distance, and visual acuity constant. Check the fine print of various DoF calculators.

 

[privatebydesign]

In this thread I have already explained the three possible comparison scenarios.

The link explains everything being discussed in more detail and more logically.

The lens doesn't change, the output for equal and relevant comparison purposes does. In and of itself the sensor size does not dictate dof, only two things do. 1, the magnification in real time of the output as you are viewing it. 2, the size of the entrance pupil in the lens or pinhole you capture the image with in the first place.

If you fully understand that the dof in a print changes as you move closer or further from it then you know what you are talking about, if you can't get your head around that concept then you really need to read the link.

 

[Loswr]

But remember that this was never a question about equivalence, but about the behavior of the lens. This is the key statement from Don's original post. It is correct.

Lenses do not magically change properties when swapped onto different bodies. The optics do not change. The photon entering the lens does not know what sensor is at the far end of the lens and can not change it's path based on that.....

Somewhere the thread was hijacked to become a discussion of CoC.

Context is important.

The moon can appear white and cratered.....

The preceding statement is correct. Is this following statement also correct?

The moon can appear white and cratered, therefore it is made of Swiss cheese.

Don made a correct statement about lens properties, and then concluded that sensor size does not affect DoF. So, if you believe he was correct, I look forward to your fondue made from moon rocks.

Sensor size does affect DoF, and it does so because CoC affects DoF, and CoC varies with sensor size. The discussion of CoC wasn't a hijack, it was the explanation.

Earlier, I believe you suggested that if you were interpreting my statements correctly, you had more reading to do. I suggest you do some of that reading before continuing this discussion…

 

[Loswr]

I think we speak about the same thing just looking at it differently. I look at it at the sensor level following the light cones behind and in front of the object plane to the image plane. I compare the relative size of the COC to the sensor size or object COC to object size...

I don't speak about 'object CoC' because it doesn't exist. All pun intended, you are clearly confused about circles of confusion. At least you have plenty of company...