From DXOMark: More pixels offsets noise3

Started May 30, 2009 | Discussions thread
Steen Bay Veteran Member • Posts: 7,418
Re: Yes, a bit tricky..

bobn2 wrote:

Steen Bay wrote:

Yes, lots of logical traps to fall into. Assuming that bigger pixels
are always better, is a bit (just a bit) like assuming that bigger
sensors are always better, and forgetting that when shooting at the
same shutterspeed and DOF, all sensor sizes will have pretty much the
same IQ, because with the bigger sensor, you'll have to use a higher
ISO value and (f-number) to get the same DOF.

...and therein lies another trap. If you don't have a constraint on
the shutter speed (like a really good tripod and no movement in the
image) then in absolute terms you can gather more photons with the
bigger sensor, and get a better image.
The corollary of the James equivalence principle that is also
commonly misunderstood is that for a given output size, no format
has an advantage with respect to diffraction blurring. You get the
same blur for a given DoF with any format (and big pixels make it
worse, not better).


Like I just said in another thread.. It all comes down to our DOF preferences, doesn't it? If you like the very shallow DOF that f/1,4 - f/4 gives you on FF, then FF is the way to go, but if you prefer a deeper, more 'normal' DOF, then FF won't necessarily give you better IQ. If you're shooting at for example iso400, f/8 on FF, then a 2x crop camera would give you just as good IQ at iso100, f/4.

I know, that with my kind of shooting, I would very rarely be able to take advantage of the potential better IQ with FF, without sacrificing some of the shutterspeed and DOF that I want. Actually I'm more tempted by a camera like the Panasonic GH1, than I am by a FF camera.

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