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Archive 2008 · DOF Diff's Between Crop & FF?

cogitech
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p.3 #1 · DOF Diff's Between Crop & FF?

Mike Mahoney wrote:

Well considering that this type of question is asked just about weekly here, and that the threads go on for many pages and leave the OP largely as confused as when he started it may not be a bad idea to keep things simple and start with the basics.

Then you can broaden the discussion to illustrate how APPARENT visual changes in DOF are seen with different sensor sizes, and other variables.

CoC is not the basics.

The basics of DOF are exactly what you described before; focal length, aperture, subject (focal) distance.

The bigger sensor offers a wider FOV, which requires the photographer to either increase the focal length or reduce the subject distance in order to maintain the same framing. These two things both directly affect the DOF.

This isn't a matter of a photographer changing his/her technique. It is a matter of the photographer maintaining the same framing across two different formats, and they do it without even realizing it. They just compose the shot as they normally would.

The visual differences are not apparent, they are very real. Increasing the focal length of the lens or decreasing the focal (subject) distance do not create "apparent" visual differences. On the contrary, they directly reduce the DOF in the photograph.

These effects are far more important (they influence the DOF of the photo much more) than the potential CoC differences between the formats.

Sep 21, 2008 at 08:18 PM

michael49
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p.3 #2 · DOF Diff's Between Crop & FF?

Photon wrote:
But is that how you photograph? I think most of us, at least when we have the chance, choose our position to get a certain perspective and relationship of objects in the frame, and from there we choose a focal length to give the angle of view that includes only the things we want to show. I think the example is well done and 100% appropriate.

That's the way I see it.

I frame my shots with my 5D/85 1.8 the same way I would frame shots with my 40D/50 1.4; the result at equal aperatures is less DOF/more subject isolation - which by the way is both good and bad, depending on what I'm trying to shoot. For landsapes FF can be a pain in the &%$#, due the amount that one needs to stop down for decent DOF.

By the way, nice examples Paul.

Sep 21, 2008 at 09:10 PM

ChrisDM
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p.3 #3 · DOF Diff's Between Crop & FF?

cogitech wrote:
Let's look at scenario:

Photographer Joe has been using his 85mm "portrait" lens on his 1.6x crop factor camera. He likes the results, but he hears that FF cameras will give him less DOF, allowing him to isolate his subject more.

So, photographer Joe rents or buys a shiny FF camera. He wants to see how his portraits are going to look, so he goes out to the park with his kid and his 85mm "portrait" lens on his new camera.

He gets home and cannot believe his eyes. "Wow! look how shallow the DOF is!" His conclusion is that the DOF is shallower on his new camera.

We all know what really happened (don't we?).

He framed his subjects as he always did. His style has not changed, after all. In order to maintain the same shots that he did before, he moved closer.

Now, IMO, it doesn't really matter whether this DOF difference is due to the camera or due to the photographer. In fact, I think it doesn't even really matter if photographer Joe is aware that he is the cause of the reduced DOF.

Bingo. And he had to step closer because his "crop" changed.. Which came first, the chicken or the egg? Does it matter? No... So more accurately we'll say that the crop changed the equivalent focal length, or subject distance... Either way, directly or indirectly, the crop factor has affected DOF.

Chris M
www.imagineimagery.com

Sep 22, 2008 at 12:56 AM

RDKirk
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p.3 #4 · DOF Diff's Between Crop & FF?

For landsapes FF can be a pain in the &%$#, due the amount that one needs to stop down for decent DOF.

Must be why nobody uses large format for landscapes.

Sep 22, 2008 at 01:48 AM

ChrisDM
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p.3 #5 · DOF Diff's Between Crop & FF?

RDKirk wrote:
For landsapes FF can be a pain in the &%$#, due the amount that one needs to stop down for decent DOF.

Must be why nobody uses large format for landscapes.

Stopping them down is very, very simple. Carrying them is not.

Sep 22, 2008 at 01:02 PM


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