Canon Full Frame Mirrorless Talk [CR1]

[Loswr]

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.

Mind. Blown.

 

[privatebydesign]

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.

Mind. Blown.

 

[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).

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

The point is, DOF depends NOT only on two things, as you claim, as the DOF formula I linked to shows.

 

[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).

Read this.

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

I know this. What I am talking about is scale invariance. Looking at the ratio of COC to image size is equivalent to the notion of magnifying a crop image more, as the ratio stays constant.

 

[Hflm]

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...

No. As I said above defining a COC (i.e. maximum blur circle for the light rays penetrating the image plane to be still envisioned as being a point for a certain output size and viewing distance) defines an object and image side COC (via ray tracing, as Zeiss mentions in their document, too). Scale invariance now shows, that the ratio of image height to this COC changes when cropping or changing the sensor. Your notion of needing to magnify a crop image more is mathematically equivalent to looking at this ratio, because it stays constant, as you scale the blur circle and image height by the same factor. It cancels out. So it is just a matter of perspective. You can say you need to magnify the image more thereby increasing the blur circles (resulting in a change of DOF), I say the size of the blur circle relative to the image size increases.

 

[romanr74]

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…

It appears to me that you are both right, yet apply different assumptions re output size/magnification. This is what matters, not the sensor size as such. The lens indeed doesn't care...

Also, please don't be simplistic about Swiss cheese.

 

[BurningPlatform]

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.

Thank you for setting me straight. Time to change my diapers, I guess.

 

[Loswr]

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).
...
The point is, DOF depends NOT only on two things, as you claim, as the DOF formula I linked to shows.

I'm sorry, but with respect, it's obvious you're having quite a bit of difficulty understanding these concepts. One of the wonderful things about math is that you can reduce equations by combining terms, rearrange terms to suit, etc. In this case, three of the four terms you list – subject distance, focal length, and CoC – are used as part of the derivation of the apparent output magnification, and thus the equation for DoF can be appropriately reduced to just output magnification and physical aperture.

 

[zim]

Well my takeaway from all this is that ignorance really IS bliss :'(

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.

How do my prints know I'm looking at them.... now I'm just scared

 

[Orangutan]

Don made a correct statement about lens properties, and then concluded that sensor size does not affect DoF.

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…

I thought you were going to cite some odd quantum effect similar to two-slit experiments that would suggest that a single photon would behave differently depending on whether it lands on a photosite near an "edge" of the sensor.

Sensor size does affect DoF, and it does so because CoC affects DoF, and CoC varies with sensor size.

It certainly can, if certain parameters are varied. Let's try again.

• Let's assume it's a studio, and it's a photo of a plastic flower. (light and subject constant)
• Both shots taken from the same tripod, at a fixed location; i.e. no change in distance to subject. (distance to subject constant)
• The final prints are done so the flower appears as the same absolute size in all three prints. (object-level magnification constant)
• Three prints are made: the FF print, the crop print, and a central crop of the FF print corresponding to the the crop-sensor print.

Is the CoC different between any two of these prints?

 

[Hflm]

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).
...
The point is, DOF depends NOT only on two things, as you claim, as the DOF formula I linked to shows.

I'm sorry, but with respect, it's obvious you're having quite a bit of difficulty understanding these concepts. One of the wonderful things about math is that you can reduce equations by combining terms, rearrange terms to suit, etc. In this case, three of the four terms you list – subject distance, focal length, and CoC – are used as part of the derivation of the apparent output magnification, and thus the equation for DoF can be appropriately reduced to just output magnification and physical aperture.

No. What you do (basically eq. (12) which is easily derivable) means you neglect the term involving the exit pupil diameter/entrance pupil diameter, which has an impact for example in the macro regime. Furthermore COC is part of the equation, explicitly. If you make these assumption you are right, but that was not set as an assumption in the beginning, instead it was _generally_ just said, by you, too, that only two parameters are important.

 

[privatebydesign]

It certainly can, if certain parameters are varied. Let's try again.

• Let's assume it's a studio, and it's a photo of a plastic flower. (light and subject constant)
• Both shots taken from the same tripod, at a fixed location; i.e. no change in distance to subject. (distance to subject constant)
• The final prints are done so the flower appears as the same absolute size in all three prints. (object-level magnification constant)
• Three prints are made: the FF print, the crop print, and a central crop of the FF print corresponding to the the crop-sensor print.

Is the CoC different between any two of these prints?

All three are the same. The magnification is the same, the aperture was the same, ergo they are the same.

The point is different sized prints are not a 'relevant' comparison. If you start changing parameters to make one the same as another then you are DXOing the results. The standard for comparisons and conclusions is same sized output, for coc calculations that standard is an 8"x10" print viewed from 12" by a human with 20/20 vision.

 

[Loswr]

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).
...
The point is, DOF depends NOT only on two things, as you claim, as the DOF formula I linked to shows.

I'm sorry, but with respect, it's obvious you're having quite a bit of difficulty understanding these concepts. One of the wonderful things about math is that you can reduce equations by combining terms, rearrange terms to suit, etc. In this case, three of the four terms you list – subject distance, focal length, and CoC – are used as part of the derivation of the apparent output magnification, and thus the equation for DoF can be appropriately reduced to just output magnification and physical aperture.

No. What you do (basically eq. (12) which is easily derivable) means you neglect the term involving the exit pupil diameter/entrance pupil diameter, which has an impact for example in the macro regime. Furthermore COC is part of the equation, explicitly. If you make these assumption you are right, but that was not set as an assumption in the beginning, instead it was _generally_ just said, by you, too, that only two parameters are important.

Sorry, I'm going to give up at this point...it's clear that the explanations by me, PBD and others just aren't sinking in, and I suspect no amount of further attempts will improve the situation. I hope that you gain a better understanding of the principles underlying DoF at some point in the future.

 

[Hflm]

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).
...
The point is, DOF depends NOT only on two things, as you claim, as the DOF formula I linked to shows.

I'm sorry, but with respect, it's obvious you're having quite a bit of difficulty understanding these concepts. One of the wonderful things about math is that you can reduce equations by combining terms, rearrange terms to suit, etc. In this case, three of the four terms you list – subject distance, focal length, and CoC – are used as part of the derivation of the apparent output magnification, and thus the equation for DoF can be appropriately reduced to just output magnification and physical aperture.

No. What you do (basically eq. (12) which is easily derivable) means you neglect the term involving the exit pupil diameter/entrance pupil diameter, which has an impact for example in the macro regime. Furthermore COC is part of the equation, explicitly. If you make these assumption you are right, but that was not set as an assumption in the beginning, instead it was _generally_ just said, by you, too, that only two parameters are important.

Sorry, I'm going to give up at this point...it's clear that the explanations by me, PBD and others just aren't sinking in, and I suspect no amount of further attempts will improve the situation. I hope that you gain a better understanding of the principles underlying DoF at some point in the future.

Dito. Neglecting terms in an equation and saying that the other one doesn't understand the issue is silly. The equation, even in the form you prefer involving magnification and aperture involves additionally COC and the
exit pupil diameter/entrance pupil diameter =P. you cn't simply ignore that. Your arrogance is ridiculous.

 

[Sporgon]

Well my takeaway from all this is that ignorance really IS bliss :'(

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.

How do my prints know I'm looking at them.... now I'm just scared

Just think about a print size of 6x4", where your image is super sharp and in focus. You're happy. Then you print it 10x8", and think "damn, my subject's not as sharp as I though it was". Then you print it A3 and realise you actually missed focus of your subject.

It's the same with dof in terms of magnification and viewing distance. If you have an image with shallow or shallowish dof, the dof that you see will vary depending on print size / viewing distance.

Clear as mud

 

[Loswr]

Dito. Neglecting terms in an equation and saying that the other one doesn't understand the issue is silly. The equation, even in the form you prefer involving magnification and aperture involves additionally COC and the
exit pupil diameter/entrance pupil diameter =P. you cn't simply ignore that. Your arrogance is ridiculous.

The entrance pupil (which is not the same as the exit pupil, even though you're lumping them together) is the optical representation of the physical aperture, the term which I used. You don't understand basic terminology, state that I am ignoring terms becuase you fail to recognize them, and accuse me of arrogance. There's really no point in responding to your ignorance and rudeness further.

 

[Loswr]

Well my takeaway from all this is that ignorance really IS bliss :'(

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.

How do my prints know I'm looking at them.... now I'm just scared

Just think about a print size of 6x4", where your image is super sharp and in focus. You're happy. Then you print it 10x8", and think "damn, my subject's not as sharp as I though it was". Then you print it A3 and realise you actually missed focus of your subject.

It's the same with dof in terms of magnification and viewing distance. If you have an image with shallow or shallowish dof, the dof that you see will vary depending on print size / viewing distance.

Clear as mud

I thought he was talking about those pictures where the eyes seem to follow you. Creepy!

 

[Sporgon]

Well my takeaway from all this is that ignorance really IS bliss :'(

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.

How do my prints know I'm looking at them.... now I'm just scared

Just think about a print size of 6x4", where your image is super sharp and in focus. You're happy. Then you print it 10x8", and think "damn, my subject's not as sharp as I though it was". Then you print it A3 and realise you actually missed focus of your subject.

It's the same with dof in terms of magnification and viewing distance. If you have an image with shallow or shallowish dof, the dof that you see will vary depending on print size / viewing distance.

Clear as mud

I thought he was talking about those pictures where the eyes seem to follow you. Creepy!

;D Ha Ha

Looking at your GIF it is apparent that Mona is having a look around her own painting to assess the DOF. From that viewing distance on (in) the original sized painting I hope Leo got all his important bits in sharp focus !

 

[zim]

Well my takeaway from all this is that ignorance really IS bliss :'(

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.

How do my prints know I'm looking at them.... now I'm just scared

Just think about a print size of 6x4", where your image is super sharp and in focus. You're happy. Then you print it 10x8", and think "damn, my subject's not as sharp as I though it was". Then you print it A3 and realise you actually missed focus of your subject.

It's the same with dof in terms of magnification and viewing distance. If you have an image with shallow or shallowish dof, the dof that you see will vary depending on print size / viewing distance.

Clear as mud

I thought he was talking about those pictures where the eyes seem to follow you. Creepy!

;D Ha Ha

Looking at your GIF it is apparent that Mona is having a look around her own painting to assess the DOF. From that viewing distance on (in) the original sized painting I hope Leo got all his important bits in sharp focus !

LOL good one

Actually Sporgon, thanks for that explanation what you describe does make sense now using those terms!
I appreciate your attempt at educating one of the great unwashed

 

[100]

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).
...
The point is, DOF depends NOT only on two things, as you claim, as the DOF formula I linked to shows.

I'm sorry, but with respect, it's obvious you're having quite a bit of difficulty understanding these concepts. One of the wonderful things about math is that you can reduce equations by combining terms, rearrange terms to suit, etc. In this case, three of the four terms you list – subject distance, focal length, and CoC – are used as part of the derivation of the apparent output magnification, and thus the equation for DoF can be appropriately reduced to just output magnification and physical aperture.

No. What you do (basically eq. (12) which is easily derivable) means you neglect the term involving the exit pupil diameter/entrance pupil diameter, which has an impact for example in the macro regime. Furthermore COC is part of the equation, explicitly. If you make these assumption you are right, but that was not set as an assumption in the beginning, instead it was _generally_ just said, by you, too, that only two parameters are important.

Sorry, I'm going to give up at this point...it's clear that the explanations by me, PBD and others just aren't sinking in, and I suspect no amount of further attempts will improve the situation. I hope that you gain a better understanding of the principles underlying DoF at some point in the future.

Dito. Neglecting terms in an equation and saying that the other one doesn't understand the issue is silly. The equation, even in the form you prefer involving magnification and aperture involves additionally COC and the
exit pupil diameter/entrance pupil diameter =P. you cn't simply ignore that. Your arrogance is ridiculous.

Sure, in macro photography DOF is also influenced by pupil magnification because there it might not be equal to 1.
Why do you think that’s not covered by the term “magnification”?

What else?
define what is 'acceptable'
CoC is arbitrary, so it’s covered by defining what is acceptable.
The Wikipedia definition: In photography, the circle of confusion (CoC) is used to determine the depth of field, the part of an image that is acceptably sharp. A standard value of CoC is often associated with each image format, but the most appropriate value depends on visual acuity, viewing conditions, and the amount of enlargement.

And the last term:
“aperture”.
Let’s take the definition of “entrance pupil” (again from Wikipedia): In an optical system, the entrance pupil is the optical image of the physical aperture stop, as 'seen' through the front of the lens system.
You still don’t think this is covered by: “the size of the aperture in the lens at capture”?

No one is saying the formulas are incorrect and no one is ignoring them or parts of them.