Canon EOS 1Ds DOF

Jon wrote in post #4182799
And how often do you crop your FF shots to 40% areally before printing them? How often do you print your "crop" shots full size, not cropped to the same extent that you crop your FF shots? DoF takes into account the final viewing size of the image, not just the circle of confusion on the sensor. You can't divorce the final viewing size from the calculation - the more you enlarge a spot, the bigger it gets, and the blurrier it looks. And it's a basic truth that you'll need to enlarge a crop more than a 35 mm/FF more than a 4x5" view camera shot in order to get that 8x10" print for your desk or mantel.

Well, I've already agreed that viewing size affects perceived DOF. But I don't necessarily agree that all images are meant to be viewed at the same size for comparison. The question was asked, is there a difference between the DOF of a cropped sensor picture and the DOF of a FF sensor picture. Those who said "yes" were coming from a certain point of view, that either you had to view the full FF picture shrunk down (or viewed from a greater distance) or you had to use a bigger focal length lens to get the same field of view. Of course either of those approaches would alter things.

What those who want to know should also understand, though, is that the center portion of the FF image is the same as the cropped sensor image (DOF-wise). The cropped sensor image is no more or less than the center portion of a full-frame image. You are allowed to view it at a smaller size for the sake of comparison of image characteristics.

Why is this useful? Well, I'm not sure why the original poster wanted to know, but at least I know that if I take a picture with my 5D I'm not changing the depth-of-field characteristics I have with my 30D -- I'm just getting more image to play with, and if I want to crop it to the same field of view as my 30D would get, if that's useful to me, I can. I shoot mostly outdoor photography and crop things all the time as it suits me. The 30D won't be "different" in depth of field as much as it will just give me less of a field of view to play with. Of course, if I change focal lengths then the comparisons switch to how different focal lengths affect depth of field.

I don't care why the original poster asks, just trying to help those who want to know to get complete understanding, not just "perceived" understanding; they are both part of the answer, as far as I'm concerned! If you don't care, then that's fine, but that doesn't mean that others here don't want to know. What I'm saying is fact, as far as I know; how you or anyone else wants to perceive things is up to you. That doesn't make my facts invalid or useless. Or do you think it does?

Tony

I suggest you go back and read some rigorous definitions of depth of field, and review the formulas used in calculating it. You'll find that they are all, 100%, based on viewing images from the different camera/lens combinations at a standard print size. If one adopts your premise, that it's all in the lens, regardless of the print size or cropping, one might as well consider that depth of field is a meaningless concept, and that if you don't like the DoF, crop the picture differently, or make a different sized print - and it won't matter because you'll look at it from the same distance, regardless of how big the print is.

You may be in the habit of taking pictures without regard to which lens you're usign on which body, and cropping to fit later on. Most of us try to find the combination of factors that'll give us the result we want right out of the camera. And that doesn't mean throwing away almost 60% of the pixels from a 5D because we weren't using the right gear for the scene. Still less does it mean accepting a photo where "just outside the field of view is a magnificent elk, but it didn't fit in the rest of the picture". Your audience just isn't going to buy that one.

Jon wrote in post #4212321
I suggest you go back and read some rigorous definitions of depth of field, and review the formulas used in calculating it. You'll find that they are all, 100%, based on viewing images from the different camera/lens combinations at a standard print size. If one adopts your premise, that it's all in the lens, regardless of the print size or cropping, one might as well consider that depth of field is a meaningless concept, and that if you don't like the DoF, crop the picture differently, or make a different sized print - and it won't matter because you'll look at it from the same distance, regardless of how big the print is.

Jon, I understand what you're saying, I really do! I guess if you don't see any use in what I'm pointing out, then 'nuff said.

What you're describing is not my approach to photography. I plan to use the right lens for the job, whatever body I use.

I will, though, give you an illustration of what I'm talking about. Last Saturday afternoon I was in a wildlife refuge near where I live to catch the beginning of the late fall/winter bird migrations. I've been there several times this year, but until Saturday used my 30D with my 100-400mm lens.

Saturday I decided to use my 5D. Unfortunately, I don't have a 500mm or a 600mm to get the same "close look" that the cropping of the 30D gives, and a teleconverter on the 400mm requires manual focus which in this setting doesn't work so well -- most of the time you are in your car shooting quickly out the window then moving on because someone else is coming up behind you.

Anyway, with the 30D I can get a shot that maybe frames a Great Blue Heron or a Snowy White Egret nicely at, say, f/5.6, giving a decent shutter speed and a nice soft background.

With the 5D, should I say "I can't get the same depth of field/soft background as I can with the 30D"? Should I take the time to change bodies? Well, no, I can take the shot, same lens/focal length, same aperture, and when I get home I can frame that bird the same way and get the same depth of field.

It's not that I take pictures "without regard to which lens I'm using". It's that when I'm using my 5D I don't have to think "this gets a different depth of field than my 30D. Dang! I'm goint to have to switch bodies!". Instead, I know that I can get the best reach that I can with the 5D and if in the end I want a 30D field of view, it's there for the cropping. Is there something wrong with that, in your opinion?

Tony

No, as long as you admit to it. That's not at all the same as claiming that DoF is the same regardless., which is clearly the impression your words left. Shooting with cropping in mind is not the same at all as using each camera and lens combination to its strengths.

Jon wrote in post #4214121
No, as long as you admit to it. That's not at all the same as claiming that DoF is the same regardless., which is clearly the impression your words left. Shooting with cropping in mind is not the same at all as using each camera and lens combination to its strengths.

I do admit to not having a 600mm lens! And, when the image warrants it, I do gladly admit to cropping and I'm happy at the latitude the 5D gives for that purpose (although I'm quite happy to prefer not cropping -- I do make full use of a wide range of lenses!).

Tony