Accurately comparing FF vs APS-C sensor performance? An open discussion.

Started Apr 8, 2013 | Discussions thread
OP VirtualMirage Veteran Member • Posts: 3,956
Re: the problem with this analysis

harold1968 wrote:

i am comparing glass as lenses are under less stress when using FF over APS-C and that effects the whole picture

Its not a lens issue per se, if you use the same lens on a APS-C camera and a FF camera the differences are plain. If you look at the MTA charts on, for example, you will see that the same lens on a FF camera can reveal typicall up to 1/3 more detail. This is an incredibly large amount.

But again, we are not talking about lenses and how much detail can be extracted.  This discussion was about sensor noise.

You are talking about light transmitted, but on DXOMARK this does not seem correlated to detail or colour depth. A fact which makes me think its missing some sizeable effect.

Detail in terms of sharpness and/or resolution, no, you are correct.  How much detail can be extracted can be limited by the type of lens used.  I never pretended this was a discussion about detail.  But color depth is correlated in the scores via a combination of Tonal Range, Dynamic Range, and Color Sensitivity.

My experience suggests precisely the opposite of your claim, and if fact that FF sensors deliver bags more sharpness across the frame on average.

I feel I may have misused the phrase higher overall image sharpness with the APS-C.  What made sense to me may not have been understood the same way.  What I meant to say is that the retains less sharpness drop off across the frame than a Full Frame.

Here is a comparison to explain what I meant:


Full Frame:

The Full Frame will still offer higher central sharpness than an APS-C, I have already said that.  But your sharpness risks dropping rapidly as you go further out to the corners, especially wide open.  Vignetting and distortion can also be more dramatic on an Full Frame than an APS-C.  All of this is usually minimized by stopping down or by investing in higher quality glass.  I didn't say any differently.

In term of you objective of matching depth of field and sensor noise, the smaller sensor always has an advantage when you are trying to keep more in focus at a larger aperture size. This is the fundamental tradeoff

Exactly, which is what I was discussing.  The purpose of this post, and what I was trying to figure out and explain, was how much of a trade-off must one make when under these circumstances.

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