Is the D7100 "iso free"?

Started May 30, 2013 | Discussions thread
Eric Fossum
Eric Fossum Senior Member • Posts: 1,322
Re: Is the D7100 "iso free"?

Andrew Stevens wrote:

No, what I was proposing is different. As I see it, at present with a 12 bit digitiser, 2096 levels are recorded in the top "hilghlights" F-stop, 1048 in the next stop, etc. Would it be possible to have a second digitser arranged the other way around to read 2096 levels in the darkest "shadows" F-stop, 1048 in the the next "shadows" F-stop etc. Could the data from the two digitisers then be combined to allow for more precision across the entire exposure range or am I compeletley wrong about this?

g the conventional ISO control

First, while i think I understand what you are saying now, referring to light levels ranges as F-stops seems just wrong to me.  But that said, ADCs are usually linear in voltage steps which makes them more or less linear in light intensity and thus non-linear as far as "stops" are concerned.

Actually, there is no reason why you can't have a non-linear ADC, usually with less resolution at higher light levels.  Making it quadratic in voltage (light) makes it linear in "stops".

You want even more non-linearity to make in non-linear in "stops" - inverted as you put it.

Sure, you can do this too.

If you want more resolution though, most engineers would opt for more linear resolution in the ADC.  Still, non-linear ADCs have some merit.  Turns out I am a co-inventor on a particular way to implement a non-linear ADC.  I dont think it was ever used in any product however.  Just seemed like a good idea at the time.

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