Canon Full Frame Mirrorless Talk [CR1]

[Orangutan]

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.

Exactly. Now please go back and read Don's post. Notice the following quotes:

Slap a 400F5.6 on each body, stand in the same spot and take a picture of the same object at F5.6....

so the subject distance is invariate, and

The fun part is the comparison between the 5DSR and the 7D2....If you crop the 5DSR image to the same field of view as the 7D2 image, the two images should be identical. Same DOF, same sampling density......

so the framing is identical, within reasonable tolerance of the hypothetical.

Don can speak for himself, but as I read his post, your observation that the images are "the same" is exactly the point he was making. Then, somehow, the discussion was diverted away from the point Don was making, and into the land of pedantry. Don, wise scholar that he is, appears to have recused himself from the pointless banter.

PBD, for the scenarios you describe I have no doubt that you are correct; however, that was not the scenario that Don described, nor what I have been commenting on since the beginning of this diversion.

 

[privatebydesign]

Look you can spin this any way you want. You are saying if you make an unequal comparison the results from two different sensors are equal; I, and the rest of the world that is describing what is actually going on, say if you make your comparison equal (same sized output, as all dof calculators do) the results are different. Duh!

If you crop a ff camera output down to a crop camera size and make the output of the two the same the results are the same, we know that. Only an idiot wouldn't get that.

But that isn't what we have been saying, we have been saying same lens, same place, different sensor, size same sized output, equals different result.

P.S. I don't recall taking exception to you or Don's comments.

P.P.S. As for your second quote from Don. Look at the second paragraph of my reply here http://www.canonrumors.com/forum/index.php?topic=32600.msg665367#msg665367

 

[Orangutan]

You are saying if you make an unequal comparison the results from two different sensors are equal;

Please read more carefully, I've tried to be explicit about this. You and I are describing very different scenarios, and you're berating me for not reaching the same conclusion from a different premise.

If you crop a ff camera output down to a crop camera size and make the output of the two the same the results are the same, we know that.

(edit)This was the whole point of the original statement...it's really no more complicated than that.

But that isn't what we have been saying, we have been saying same lens, same place, different sensor, size same sized output, equals different result.

In that scenario you would be correct, but that was NEVER the original premise, it was the mutated premise. The original premise was same lens, same place, different sensor, different sized output, equals same result (within the cropped area).

P.P.S. As for your second quote from Don. Look at the second paragraph of my reply here http://www.canonrumors.com/forum/index.php?topic=32600.msg665367#msg665367

Yes, I've never had a problem with that explanation. The problem is that you keep insisting on making the output prints the same size, which was not the original premise. The original premise was same scaling, not same final size. I.e., an object within the frame would have the same absolute size.

 

[Orangutan]

My previous reply was not very good, so I'll try again. I generally don't like to delete posts, so I'll leave it unless it becomes a distraction.

If you crop a ff camera output down to a crop camera size and make the output of the two the same the results are the same, we know that.

OK, we're off to a good start.

Now, Don essentially set up that very scenario to explain that the lens does not change its behavior if it's moved to a crop camera, but then added a throwaway line that could have been a bit ambiguous.

DOF does not change because you have moved between crop and FF

Neuro decided to "correct" this statement by saying this:

if you actually change nothing else, i.e. keep subject distance and aperture the same, use the same lens and focal length, and only swap out the camera…the depth of field will actually be shallower with the smaller sensor. So yes, either way sensor size absolutely affects DoF

Which is correct, assuming the final output sizes are the same between the FF and crop. However, as you note above, if you scale the same rather than print the same absolute final output size, then the two are the same; more precisely, they are identical by definition.

Now, since Don's statement was about the behavior of the lens, rather than the printer, I chose to be charitable in my reading, and assumed that Don (an obviously intelligent person), would select the print option that made his statement correct, and pointed out to Neuro that has was making assumptions that were not explicit in Don's setup.

And then the thread descended into people talking past each other, and not listening.

In summary, this whole tempest in a flea's anus was over a throwaway line that made an assumption about print size, and whether "all else being equal" is possible in these scenarios. It really was a trivial thing.

 

[privatebydesign]

If you go back to the post of Don's you keep mentioning, the original premise of that was nothing to do with output size, it was all about reach being a function of pixel density, which is also a seriously flawed concept.

Neuro's correction was in line with accepted terminology with regards dof calculations, Don's comment needed a "charitable" addition to make any sense, that that addition meant his suggestion fell outside the standard accepted terminology is not Neuro's or my fault.

You gave Don a pass on an ambiguous statement that fell outside standard calculation practices, others didn't.

 

[Hflm]

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.

Again selectively neglecting information.
The ratio of exit pupil diameter/entrance pupil diameter =P is part of the eq., even if we express the entrance pupil diameter in terms of the aperture, you still have the exit pupil diameter. This relation is different for different lenses, so a parameter to incorporate. Fixing magnificaton (M) and aperture (A) furthermore means that you get a linear relationship between focal length and object distance. So you have the freedom to change object distance v and focal length f if desired, as long as you follow the linear relation. so DOF = f(M,A,P,COC). Only if you make certain assumptions (e.g. fix the format, fix P), then you can reduce the dependency on two parameters, alone.

 

[Loswr]

Now, since Don's statement was about the behavior of the lens, rather than the printer, I chose to be charitable in my reading, and assumed that Don (an obviously intelligent person), would select the print option that made his statement correct, and pointed out to Neuro that has was making assumptions that were not explicit in Don's setup.

And then the thread descended into people talking past each other, and not listening.

In summary, this whole tempest in a flea's anus was over a throwaway line that made an assumption about print size, and whether "all else being equal" is possible in these scenarios. It really was a trivial thing.

Sorry, but no. Perhaps your objections to my correction of Don's erroneous information could be termed a "throwaway," but the salient bit is that Don made an incorrect statement which I corrected. Perhaps it's worth revisiting Don's original post, which to avoid any confusion I will include in its entirty, even though only the last part is relevant to this discussion:

Reach is a function of pixel pitch not sensor size. If the pixel density of 5DSR is (give or take) pretty similar to EM-1.2 they both have the same 'reach' with a 300mm lens.
FOV is irrelevant if you are focal length limited.

Exactly!

Look at the 1DX2, the 5DSR, and the 7D2....

Slap a 400F5.6 on each body, stand in the same spot and take a picture of the same object at F5.6....

Let's call the 1DX2 shot the "standard image" to compare against.....

The 5DSR image will have an identical field of view as the 1DX2 image and the DOF will be identical, but the image will be sampled more densely.

The 7D2 image will have only 62% of the field of view of the 1DX2 image, the DOF will be identical, and the image will be sampled more densely.

The fun part is the comparison between the 5DSR and the 7D2..... both cameras have the same pixel pitch and are approximately at the same level of sensor technology... If you crop the 5DSR image to the same field of view as the 7D2 image, the two images should be identical. Same DOF, same sampling density......

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.....

DOF does not change because you have moved between crop and FF. DOF changes when you walk closer (or further) from your subject (framing) or when you change the aperture of the lens.

He has two main points. First, that "reach" is a function of pixel density. No argument there. His second point, which I highlighted, is that depth of field does not change merely by swapping cameras with different sensor sizes. That's wrong. He's absolutely correct that significant effects on DoF come when you compare crop and full frame and alter other parameter(s) to make the framing identical. You change the subject distance, or the focal length, and obviously you have changed DoF. But if all you do is move between crop and full frame (his words), the CoC changes and therefore, the DoF changes.

His point about sensor size and DoF is straightforward, it's just incorrect. Even if you don't understand the math or the concepts, all you have to do is go to your favorite online DoF calculator (e.g., DOFMaster), pick a focal length, aperture, and subject distance, then change only the camera choice between a full frame sensor camera and a crop sensor camera, and see what happens to the DoF that the calculator reports. If it remains the same, Don is correct. If it changes, he's wrong.

If you want to charatibly believe that Don is correct because he was assuming the crop sensor image would be viewed on an iPad while the FF sensor image would be viewed on a 19" monitor, and that such an assumption is so inherently logical that there was no need to even state it, that's your business...although frankly, it's quite an asinine assumption.

Ps. As for it being a trivial thing, let's take Don's example of crop versus full frame and a 400/5.6. A typical use case for me would be a small perched bird at about 6 m distance. In that case, the DoF calculator reports DoFs of 7.1 cm and 4.5 cm for FF and crop, respectively. To me, having the entire bird versus only half the bird in focus is not trivial.

 

[Orangutan]

If you go back to the post of Don's you keep mentioning, the original premise of that was nothing to do with output size, it was all about reach being a function of pixel density, which is also a seriously flawed concept.

It would have been fine to point that out, rather than start a diversion on CoC. It would have been more useful and more charitable...and less wasteful of time and energy.

Neuro's correction was in line with accepted terminology with regards dof calculations, Don's comment needed a "charitable" addition to make any sense, that that addition meant his suggestion fell outside the standard accepted terminology is not Neuro's or my fault.

You gave Don a pass on an ambiguous statement that fell outside standard calculation practices, others didn't.

Again, rather than say "that's WRONG," he could have simply said "standard DoF comparisons assume the same output size, so maybe you should tighten up your terminology here." or "this is only true if you print at the same scale." Instead, he tried to make it a fundamental issue of misunderstanding. In Don's case, I think it's more likely he was focusing on the point of his explanation, and was a bit too casual for Neuro's territorial peer-review. As an example, suppose someone wrote that the area of a circle is given by

A = πR2

The appropriate response is not to say "that's wrong!" and then give a lecture on how the area of a circle is known. The appropriate response is to say "yes, that's correct, but the convention is to use a lower-case r to refer to the radius, and that capital R often refers to something else.

 

[Loswr]

Again, rather than say "that's WRONG," he could have simply said "standard DoF comparisons assume the same output size, so maybe you should tighten up your terminology here." or "this is only true if you print at the same scale." Instead, he tried to make it a fundamental issue of misunderstanding. In Don's case, I think it's more likely he was focusing on the point of his explanation, and was a bit too casual for Neuro's territorial peer-review. As an example, suppose someone wrote that the area of a circle is given by

A = πR2

The appropriate response is not to say "that's wrong!" and then give a lecture on how the area of a circle is known. The appropriate response is to say "yes, that's correct, but the convention is to use a lower-case r to refer to the radius, and that capital R often refers to something else.

As I pointed out above the difference is not merely a convention, nor is it trivial. Try this:

"If you change the focal length with a zoom lens, the subject framing does not change."

That's a simple, straightforward statement that is manifestly wrong. What you're suggesting is such a statement is correct if phrased as:

"If you change the focal length with a zoom lens, the subject framing does not change assuming you change the subject distance by moving closer or having the subject move further away by a distance that exactly negates the change in focal length, or that you crop the image taken with the shorter focal length so that the framing is the same."

Sure, if you slap enough assumptions onto a false statement you can make it true, in a very specific set of circumstances. But that's rather silly...and doesn't change the fact that the original statement as written is incorrect.

 

[rrcphoto]

wow...

someone really spiked this thread.

to be honest, it's a far more complicated subject than most give it credit for, and it's going to be even far more complicated when high mp cameras get out in the wild such as the 120MP DSLR that canon will release sooner or later - which will have a *higher* pixel density than any m43's, asp-c or full frame camera body.

 

[Mikehit]

I went away for a couple of days and this damned discussion exploded. So rather than wade through pages of counterclaims and varying assumptions, which in true internet fashion it is hard to tease out fact, misunderstanding and opinions, I found this article if it helps:

http://www.clarkvision.com/articles/dof_myth/

The Canon 1D mark II camera has a pixel pitch (pixel spacing) of 8.2 microns. The Canon S70 pixel pitch is 2.3 microns. The ratio of the pixel pitches is 8.2/2.3 = 3.56. If we keep the f/ratio constant between the two cameras (see Figure 1, bottom two frames, images at f/3.5), the larger pixel camera has a much smaller depth of field. But if we equalize the apertures, and and exposure times (1/8 second, top two frames in Figure 1), the two cameras record the same depth of field and collect the same number of photons in the pixels in each camera. To make the depth of fields equal, the focal lengths have the same ratio as the ratio of the pixel pitch, and the f/stop changes by 3.7 stops (f/3.5 on the small camera to f/13 on the large camera: f/3.5 * 3.56 = f/12.5). The ISO on the large pixel camera was increased by the same factor as the reduction in light due to the small aperture to give the same relative intensities in the image (ISO 50 * 3.56 * 3.56 = 634, close to the nearest available ISO of 640). Note: changing ISO does not change the number of photons recorded, only how the signal is amplified.

It shows the complexity of the discussion where when talking about aperture are you referring to the f/ratio (f stop value, AFAICT) or the physical aperture size. And pixel density may or may not come into it.

Bleah!

 

[privatebydesign]

I went away for a couple of days and this damned discussion exploded. So rather than wade through pages of counterclaims and varying assumptions, which in true internet fashion it is hard to tease out fact, misunderstanding and opinions, I found this article if it helps:

http://www.clarkvision.com/articles/dof_myth/

The Canon 1D mark II camera has a pixel pitch (pixel spacing) of 8.2 microns. The Canon S70 pixel pitch is 2.3 microns. The ratio of the pixel pitches is 8.2/2.3 = 3.56. If we keep the f/ratio constant between the two cameras (see Figure 1, bottom two frames, images at f/3.5), the larger pixel camera has a much smaller depth of field. But if we equalize the apertures, and and exposure times (1/8 second, top two frames in Figure 1), the two cameras record the same depth of field and collect the same number of photons in the pixels in each camera. To make the depth of fields equal, the focal lengths have the same ratio as the ratio of the pixel pitch, and the f/stop changes by 3.7 stops (f/3.5 on the small camera to f/13 on the large camera: f/3.5 * 3.56 = f/12.5). The ISO on the large pixel camera was increased by the same factor as the reduction in light due to the small aperture to give the same relative intensities in the image (ISO 50 * 3.56 * 3.56 = 634, close to the nearest available ISO of 640). Note: changing ISO does not change the number of photons recorded, only how the signal is amplified.

It shows the complexity of the discussion where when talking about aperture are you referring to the f/ratio (f stop value, AFAICT) or the physical aperture size. And pixel density may or may not come into it.

Bleah!

You can look at it as complicated, or really simple. Look at it like this:-

The two rulers are the same size to you in real time in both pictures, ergo magnification is the same; the actual physical aperture opening in the S70 image is smaller than the one from the 1DMkII, ergo the 1D MkII image has less dof. Simple.

 

[chrysoberyl]

I am really glad that I don't have to understand the last several pages to take pictures!

What I really want to know is whether my next camera should be mirrorless.

 

[LonelyBoy]

What I really want to know is whether my next camera should be mirrorless.

Yes. No. Maybe. Sure. Or not.

 

[bdunbar79]

I am really glad that I don't have to understand the last several pages to take pictures!

What I really want to know is whether my next camera should be mirrorless.

Well, some might think having a mirror in the camera or not changes the DOF. I mean, it's as bat crap crazy as thinking pixel pitch affects DOF.

 

[chrysoberyl]

I am really glad that I don't have to understand the last several pages to take pictures!

What I really want to know is whether my next camera should be mirrorless.

Well, some might think having a mirror in the camera or not changes the DOF. I mean, it's as bat crap crazy as thinking pixel pitch affects DOF.

Ha - agreed!

I use my viewfinder. I don't have tiny hands, so I don't want a small camera; my 80D is about as small as I want. Gravitation lensing is the only thing that really impacts DOF.

 

[okaro]

Ps. As for it being a trivial thing, let's take Don's example of crop versus full frame and a 400/5.6. A typical use case for me would be a small perched bird at about 6 m distance. In that case, the DoF calculator reports DoFs of 7.1 cm and 4.5 cm for FF and crop, respectively. To me, having the entire bird versus only half the bird in focus is not trivial.

The only reason you have more of the bird in focus with FF is that the both is smaller so it looks to be in focus. If you were to crop the image you would get exactly same results (ignoring things like the pixel density).

There seems to be two ways too look at the depth of field: abstract and concrete. The abstract view focuses of the formulas. It totally ignores subject as it is not relevant to the calculations. The concrete view starts with the subject and the person using it wants it in same size so he may say that it is not the sensor size but the fact that one has to change the distance that counts. That makes no sense to the one having the abstract view (like someone calculating DoF markings on lenses) as he does not care about the subject but for him distance is a fundamental parameter. The skill is to move between these views. Your example hinted a difficulty from moving from the abstract to the concrete. Someone with a cop body would have to use 250 mm f/3.5 for the same. In reality he would probably use 250 mm f/5.6 and get more DoF but also more noise. But then his lens would cost only a fifth of what 500 mm f/5.6 costs.

When comparison crop and FF one has to decide what to keep same and what to change. The view changes depending this. The reality does not. It is like the blind men touching an elephant. Two different views can be correct. On the other hand this does not mean that everything is correct. Simply put to get identical results on crop one has to divide the focal length and aperture by 1.6 and the ISO value by 2.56. In many cases the result especially with aperture falls outside what normal lenses can produce. If they did not there would be little sense in having a FF body.

 

[bdunbar79]

<The only reason you have more of the bird in focus with FF is that the both is smaller so it looks to be in focus. If you were to crop the image you would get exactly same results (ignoring things like the pixel density).>

You're missing the point. There is only ONE way too look at it. One correct way and why nobody can understand this simple concept is well beyond me. Same lens, same aperture, same subject distance, using a MF, FF, and crop body, all yield different DOF. Period. That's all you really need to understand: sensor size affects DOF all else equal.

Why can't anybody get this simple point? Why do you think the subject appears smaller the larger the sensor you go?

 

[okaro]

I am willing to bet that the average consumer does not care if it is mirrorless or not... All they care about is does it take good pictures in "green box" mode.... although, with FF, the odds are much better that it will be used with a second lens and even taken out of automatic mode.....

We CR readers do not represent the average consumer.....

FF cameras are not for average consumers. FF is for serious hobbyist and professionals.

 

[okaro]

<The only reason you have more of the bird in focus with FF is that the both is smaller so it looks to be in focus. If you were to crop the image you would get exactly same results (ignoring things like the pixel density).>

You're missing the point. There is only ONE way too look at it. One correct way and why nobody can understand this simple concept is well beyond me. Same lens, same aperture, same subject distance, using a MF, FF, and crop body, all yield different DOF. Period. That's all you really need to understand: sensor size affects DOF all else equal.

Why can't anybody get this simple point? Why do you think the subject appears smaller the larger the sensor you go?

I am not missing anything. I know the math. I have calculated these. You started talking about practical situations of shooting a bird at six meters. Then you have to step outside the formulas an think what they mean in that practical situation. They mean just that the bird is smaller and therefore looks sharper. You could just as well shoot from further back to get similar result. 500 mm f/5.6 at 6 meters on FF gives DoF 7 cm. With crop it gives only 5 cm but if you move back to 9.6 meters you get 12 cm DoF. Similarly if you reduce the focal length to 250 mm and shoot at 6 m you also get 12 cm. (This is not to imply that they are always same though they seem to be very similar). Of course the perspective changes if you change the distance.