E-M5 has DR 13!

Started Apr 13, 2012 | Discussions thread
dgrogers
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Re: hard to get 13 bits of DR from 12-bit RAW files [n/t]
In reply to SphericalAberration, Apr 14, 2012

I always thought dynamic range is the difference between the brightest point the sensor can distinguish detail and the darkest point. Bit depth is simply how many steps this difference can be displayed in (12 bits only allows so many numbers/steps). The more dynamic range you have, the more bits you need to display differences in brightness smoothly.

SphericalAberration wrote:

Let me have a go at trying to put this straight :
Signal to noise ratio is not the same as dynamic range.

If the sensor full scale corresponds to 13EV of light above dark = 6.02 x 13 dB = 78.26 dB = FS.

Likewise for an ADC the best possible FS SNR = 6.02N + 1.76 dB

For 12 bit it's not possible to have signal to noise ratio SNR better than 74dB.

However notice that the SNR plots from the cameras are way below this number e.g. 42dB.

That is because each ADC bit change corresponds to more than 6dB or 1EV change in light level.

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