Dynamic range and RAW file "bit depth"

Started 3 months ago | Questions thread
Jack Hogan
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In reply to completelyrandomstuff, 3 months ago

Completelyrandomthoughts, I don't mean to sound condescending but there is a lot of misinformation being put forth in this thread.  This is not the Open forum. Many contributors here (and I am not including myself) have intimate knowledge of how a camera's hardware and processing works. Therefore it is best to phrase speculative statements as questions so that when one gets rebuffed one does not get one's nose put out of joint.  And whoever will read the thread in the future will not walk away more confused than when they started.

completelyrandomstuff wrote:

That would make sense. The nonlinearity will begin the moment there are interactions between the electrons deficiency in the well. It takes more energy to remove an electron from a more negatively charged body. So that 'compression' is not necessarily engineered, I think it's a consequence of physics.

Is this compression typically visible/usable by a photographer?

However, the way you digitize the signal, is engineered.

In what way?  Are you referring to the ADC or processing after it? AFAIK all current DSLR sensors have linear ADCs.

The camera devotes the least digitization levels to lowest signals and that should, in theory compensate for the nonlinearity of the relationship between photon flux and well filling.

I thought all current DSLR ADCs were linear.  With a very few exceptions (like that mentioned by GBG) aren't non-linearities near saturation clipped away by camera designers therefore not getting stored in the Raw data?

This is why DXO reports the S/N ratio at 18% btw. This 18% corresponds to 50% gray.

Does 18% of saturation in the raw data correspond to middle gray in most DSCs?  Wouldn't DxO instead report SNR at 18% because that's more representative of perceived image noise than reporting it at 0.1% or 99%?

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