D3 sensor efficiency

Started Nov 18, 2007 | Discussions thread
OP ejmartin Veteran Member • Posts: 6,274
Re: Maximum black with reflective target

For the purpose of measuring the read noise, you don't need to go all the way to black; in fact this is somewhat preferable for Nikons due to the problem that Nikon clips the blacks in the raw data, thereby skewing the std dev of the deepest shadows, whose ave raw level is within a std dev or two of zero. Instead one can measure the noise in deep shadows somewhat above black and extrapolate the result to zero.

For my rough measurements with the D3, read noise was indeed measured by extrapolation from nonzero values, taking care of the narrowing of the st dev near black due to the fact that Nikon clips the blacks rather than adding a bias. For details see the following:
http://www.openphotographyforums.com/forums/showpost.php?p=38602&postcount=6
--
emil
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http://theory.uchicago.edu/~ejm/pix/20d/

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