PIX 2015

Why won't the D600 have better high ISO performance than D800?

Started Sep 13, 2012 | Discussions thread
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Luke Kaven
Veteran MemberPosts: 5,581
Re: don't larger pixels grab more light?
In reply to Dan, Sep 14, 2012

Dan wrote:

Let's say we have a 1pixel sensor vs. a 100pixel sensor. The pixels of the 1 pixel sensor obviously get more light because they are 100 times bigger, getting that much more light.

Noise is measured per unit area of the sensor . Having 4 pixels in the space of one pixel actually confers some noise improvements.

The best explanation of this is in Emil Martinec's papers on noise calculation.

"The raw value is proportional to the number of photons collected; combining pixels, the photon counts add and so the raw values should be added together:

S = S1 + S2 + S3 + S4

The noises combine in quadrature:

N = sqrt[ (N1)2+(N2)2 +(N3)2+(N4)2 ]

If the raw values are approximately equal, and the noise contributions are approximately equal, the aggregate signal is four times that of the individual pixel; on the other hand, the aggregate noise is about twice the noise of the individual pixel. Thus the "superpixel" of four pixels binned together has twice the S/N ratio of any of its component pixels."

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