Dynamic range and RAW file "bit depth"

Started 8 months ago | Questions thread
Jack Hogan
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Re: This is a really clear explanation
In reply to completelyrandomstuff, 8 months ago

completelyrandomstuff wrote:

http://www.earthboundlight.com/phototips/nikon-d300-d3-14-bit-versus-12-bit.html

It may be clear but it is quite old and misleading:

1) the D300 actually lowers read noise in 14-bit mode vs 12-bit by slowing the readout of the sensor (that's why FPS drop to 2.5FPS at 14-bit vs 6FPS at 12-bit), so if he took those images with it we really cannot conclude anything from them
2) The physics of light wrt photography is 100% linear (that is more Luminance = proportionately more photons = proportionately more electrons = proportionately higher ADUs), and linear light is what the human visual system expects to 'see'. The fact that our eyes and brains respond logarithmically to a linear stimulus has absolutely nothing to do with whether scene information is fully encoded by a 12-bit linear ADC or whether a 14 bit linear ADC would be preferable.
3) He used ACR and CNX ADL to 'recover' shadows. And we all know the amount of non-linear processing those algorithms use.

So it would be useful to see a more scientifically done test with today's cleaner cameras.

Jack

PS Plus let's not forget that DR requires defining a threshold for the denominator, which in this discussion has been implicitly assumed to be either the read noise or the signal at which SNR=1. Many cameras today show information well into 15 stops down from saturation (the D7k for instance). Very poor quality, but it's still there and part of your picture.

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