DOF comparison FF v. 1.6 crop

I am relatively new to this forum and was wondering if anyone had done a comparison of the difference in depth of field of full frame cameras (now that we have the 5D out there along with the mega-bucks pro models) versus the 1.6 crop cameras.

I realize there are sites that give you the number crunching but I was more interested in looking at actual pics, as in the bokeh threads that I found very interesting.

Hopefully this will peak some interest.

Thanks.

John

Here you go: http://www.dpreview.co​m …OS5D/Images/ful​lframe.jpg

http://www.dpreview.co​m/articles/canoneos5d/

Grego - I think that's comparison of the field of view, not depth of field.

Yonni - given the same field of view on both cameras, to achieve the same depth of field, you will need to stop down by a factor of 1.6 on the full frame camera.

For example, if on 20D you're shooting with an aperture of f/10 then GIVEN THE SAME FIELD OF VIEW, you'll have to shoot at f/16 on the 5D

Does that answer your question?

Yeah, you are right. Whoops, Sorry. I guess I didn't sleep enough at the library at UCLA.

Thanks Doc. It couldn't be simpler.

I don't know where to find sample shots for a direct comparison, but here's an article that explains the difference.

Doc's formula holds true IF you're shooting from the same distance and the same field of view is obtained with proportional focal lengths, such as an 80mm lens on a full-frame camera vs. a 50mm lens on a 1.6 camera.

Here you go: http://www.outbackphot​o.com …hnique/essay07/​essay.html

Thanks, Rene'
The images in that article really tell a story. The difference is more pronounced than I would have guessed.

Doc -

First time I've heard this DOF explanation and it seems to be approximatley true under some conditions but not all. Do you have a source? Did you figure it out from the basic lens equations?

What is true is that the hyperfocal distance for a given FOV is the same if you adjust the aperture so as to correct for the crop factor difference.

I did figure it out from the basic equations... but it was eight months ago, and I have successfully forgotten all of them.

Maybe I'll post something about it later.

Yonni, the answer to your question is somewhat mixed depending on what you are doing with the image. Comparing the two cameras using the same lens can be done two ways. One is to take a photo of the same subject at the same distance and print both to the same size print. The apparent depth of field will be less for the 20D (though I have never calculated how much) because you are taking a smaller image (the size of the sensors is what you need to compare here) and blowing both up to, say, 8 x 12 inches. The 5D starts with a larger image and requires less magnification to arrive at the 8 x 12 print.

On the other hand - if you blow up the SAME PORTION of the subject from both cameras to produce essentially two identical prints (losing much more of the 5D image due to cropping), I believe that you will see essentially identical depth of field. In reality, the 20D image will be sharper because the density of the pixels on the sensor is greater than the 5D's sensor. In other words, you'll have more pixels representing the image cropped from the 20D image than you will for the 5D image. Again, remember that you are taking two shots from the same position, and cropping both cameras' images to produce identical subject material on an identical sized print.

Doc,
I am guilty of beating the now expired horse - but I just wanted to follow up on this thread.

I had posted an earlier question asking, in effect, where did you get your facts from. I didn't think it was accurate.

Turns out, what you said is a good approximation, if I am to trust someone who has written one of the best DOF articles I know.

From Paul van Walree
http://www.vanwalree.c​om/optics/dof.html

"R" can be interpreted as our friend, the crop factor, when field of view is kept constant for the same lens on cameras of differing format.

This rule is, in fact, a reasonable way to think about the differences in DOF given the same field of view with the same lens on cameras with different crop factors.

Doc - thanks for the insight.

Awesome bit of info and news to me. But makes perfect sense.
Added to the "X-Factor" link page

Relationship between sensor size and DOF

A friend is killing me by trying to convince me that if you increase the sensor size, say full frame instead of 1.6x APS-c, you will decrease your Depth of Field... My understanding is that DOF is a phenomenon of F/stop and has nothing what so ever to sensor size.
Can any one throw a light in my darkness?!

don't know much about it, but the pics of a full frame have a sort of 3d effect to them, might be something in that sense