More Depth Of Field

[beano500]

So maybe I'm missing something about depth of field. Help me get my head round this.

A point is said to be "in focus" if the circle of confusion is small enough, right?

Now if we switch from 35mm to APS sized sensor, using the same lens does this effect depth of field? If so - no wonder a DOF scale isn't used?

And if DOF is affected - which way?



First thought is that the circle of confusion has to be smaller with a smaller sensor - thus reducing DOF???

[flameop]

..sure I read that say you have set F2.8 on a APS then you will get the same DOF as F4 on a full frame SLR. Got confused at that point and stopped reading! lol..

As were talking fstops and DOF.. how do you set the DOF on a motion picture camera? say a 35mm one.. T-stop? (transmission) the same as fstop ?

[V6GTO]

It'll be the same. The same image reaches the sensors, the smaller sensor just records a smaller part of it.
Clear as mud

Martin.

[Gemm]

I'd just get on with shooting if I were you.

[mmertens]

Google for "sensor size DOF" and you shall find multiple sites with answers. Basically, if the field of view remains the same, DOF increases when sensor size gets smaller - which you may have noticed, all the little digital P&Ss have much greater DOFs for more or less the same picture, and don't allow you to "throw out of focus" the background as well as a DSLR can. As for the why - see aforementioned pages, it is apparently not so straightforward as you might think.

Maarten

[poah]

a cropped sensor gives more DOF than the equivent 35mm frame.

[Stu Hill]

I thought that it was all to do with enlargement size. If you use the same negative, the contact print looks really sharp, at 10x8 you get much more DOF. So large neg gives very sharp image (less DOF) at the same size reproduction over a smaller neg.