D3 sensor efficiency

Started Nov 18, 2007 | Discussions thread
OP ejmartin Veteran Member • Posts: 6,274
Re: Operational definitions

JimPearce wrote:

Could you explain how this notion of dynamic range is related to the
dynamic range we can use in an image, and possibly other useful
things like latitude?
--

I'll give the example of the 40D, which John Sheehy tested to have 11.1 stops DR according to the engineering definition:
http://www.pbase.com/jps_photo/image/87419422/original.jpg
Imaging-resource ran a step-wedge raw image through Imatest
http://www.imaging-resource.com/PRODS/E40D/E40DIMATEST.HTM

and found the DR according to various "quality" standards -- where the noise reaches various fractions of the luminosity jump between steps; low quality is where the noise is 1 stop, medium half a stop of noise, medium high a quarter stop, and high quality is .1 stop of noise. IR finds that the low quality DR is 11.2 stops (interesting, since the DR in such a test cannot exceed the engineering DR), the medium quality DR is 10.1 stops, medium-high is 9.3 stops, and the high quality DR is 7.7 stops. So as your standards go up as to how small the noise should be relative to the illumination level, the DR goes down.

So the engineering DR corresponds rather closely to what others call "low quality" DR. Knowing the read noise and the quantum efficiency of the sensor, one can calculate the DR according to various other quality standards since these two figures entirely determine the noise characteristic as a function of exposure. I have not bothered to do so however.

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