d7100 crop mode

[Tbolt47]

The reason for the confusion on this question is that the DOF actually decreases when you crop, due to the increased magnification. So, why would I claim that you get more DOF with the 1.3x crop? Say you're shooting at 300mm and f5.6 with the D7100. The decrease in DOF from the 1.3x crop won't be as much as you'd get by shooting at 375mm with the same framing. It's that simple.

 

[Mako2011]

Read it and weep: http://www.dpreview.com/forums/post/53076207 . Feel free to weigh in over there.

Apples and oranges...he's not speaking to crop mode and DoF but equivalence...I think. He even indicates a lens and aperture change...which in fact results in a different DoF (to be expected) when you plug the 100mm 2.8 and 135mm 3.5 in the calculator you linked. Pose the correct question. "If you crop the image in-camera does the DoF change?" Also, note that we actually have photographic evidence here in two posts to consider.

--
My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)

 

[JimPearce]

That we're dealing with the 1.3x crop in the D7100. By all means post some of your photographic "evidence" over there. I can't wait.

 

[jimoyer]

That we're dealing with the 1.3x crop in the D7100. By all means post some of your photographic "evidence" over there. I can't wait.

 

[alcaher]

it would be great if this thread gets 150 posts

 

[JimPearce]

If people here think they have evidence that the prevailing theory of DOF is wrong, that is the appropriate forum in which to hash it out.

 

[jimoyer]

I certainly understand what you're saying Jim, but there's some competence here as well, and I asked what I did only because the original question referred specifically to how it relates to the D7100's crop mode and because of that is every bit as relevant to the DX forum IMO.

Regards,

John

jimoyer

 

[Mako2011]

If people here think they have evidence that the prevailing theory of DOF is wrong, that is the appropriate forum in which to hash it out.

--
Jim

Already going nicley here. Don't forget why the calculators don't always match the evidence.

Depth of field is measured with a CoC (Circle of Confusion) and the calculators apply a different CoC in their calculation based on the sensor size. You can only say that you have 5 feet of depth of field if you have some objective measure for measuring depth of field. Since there's no such thing as perfectly in focus, then perfectly blurred at just a slightly different distance, but rather it's a continuum from sharp to blurred, one has to be able to say how blurred is it and establish a threshold that can be used to measure the edge of the depth of field. This amount of blur is encapsulated in the CoC number.

Because a smaller sensor image must be magnified more than a larger sensor to product the same output (view on screen or in print), this change in magnification affects the perceived depth of field (also affects the perceived noise). Because of the difference in magnification, these calculators use a different CoC number for different sensor sizes in order to try to compare apples to apples in some similar final output. With crop mode, cropping in-camera, there is no change in magnification (note the example shown here in this thread) and it's no different than taking scissors to a picture and actual DoF does not change. Taking a shot of the elephant, in normal mode and in crop mode, the elephant is still the same number of pixels across in both

 

[JimPearce]

Cropping makes the actual image smaller. It then requires more magnification to get to 8" x 10". QED

 

[wildlifr]

it would be great if this thread gets 150 posts

You might be surprised how many times this question has maxed out a thread. Bottom line is this: if you look through your viewfinder and realize that you could use crop mode to capture the part of the scene that you want, then the DOF will be no different than if you captured it with the full sensor and cropped with software (see my ruler example below). On the other hand, if you decide to use crop mode and have to move further away from the subject to get the framing you want, then the DOF will be deeper than if you had used the full sensor and were closer to the subject, assuming the same focal length and aperture.

 

[Mako2011]

Cropping makes the actual image smaller. It then requires more magnification to get to 8" x 10". QED

--
Jim

Cropping does not change the size of the subject. Cropping does not require more magnification nor does it require 8 x 10. That's why the DoF does not change when you simply select 1.3 crop mode and take a pic. Note the ruler example posted below. Crop mode does not change CoC like the online DoF caculator does.

 

[JimPearce]

A sensor cropped to the 1.25x dimensions would record exactly the same shot. You thus find yourself in the position of implicitly arguing that all formats have the same DOF. What needs to be investigated is what it is about these ruler examples that makes them anomalous.

 

[wildlifr]

A sensor cropped to the 1.25x dimensions would record exactly the same shot. You thus find yourself in the position of implicitly arguing that all formats have the same DOF. What needs to be investigated is what it is about these ruler examples that makes them anomalous.

 

[JimPearce]

At any rate, it looks to me that The Sage Knows has unmasked your "experiments" in the other forum.

 

[wildlifr]

At any rate, it looks to me that The Sage Knows has unmasked your "experiments" in the other forum.

 

[JimPearce]

http://www.dpreview.com/forums/post/53082495

 

[wildlifr]

http://www.dpreview.com/forums/post/53082495

 

[JimPearce]

http://www.dpreview.com/forums/post/53082495

 

[wildlifr]

http://www.dpreview.com/forums/post/53082495

--
Jim

Yes, that's the one I was referring to. Here is his quote:

"The DOF did not change because you've done the same thing, once by using the camera crop function, the other time by using a post processing program to crop."

This is all I've been saying all along. If you choose to crop with a program in PP or use crop mode in the camera, the result is identical with respect to DOF.

The lower DOF we're talking about in the crop results from the additional magnification required to bring it to the same output size as the shot from which it was cropped. Now the effect of that 1.25x magnification on DOF is indeed subtle - the difference between f4 and f5.

But characterizing it as "subtle" is being generous. As I've shown with my ruler example, a change in DOF that results from different magnification levels isn't even observable with a graduated ruler, viewed at 100%, 6 inches from the screen, so how relevant can it possibly be in real life shooting?

--
Jim

 

[Mako2011]

http://www.dpreview.com/forums/post/53082495