Howcome the same data are spread over a larger contrast range when you
increase the ISO?
Jostein
Den 18.05.2016 20.37, skrev Larry Colen:
I expect that the answer to this question is "Yes, but it makes no
practical difference".
Let's say a camera has a 12 bit D/A and at base ISO of 100 has 10 stops
of dynamic range. In theory the chart would look something like this:
DR ISO
__ _________
10 100
09 200
08 400
07 800
06 1600
05 3200
04 6400
03 12800
02 25600
01 51200
Lets say that you are doing a macro photo of a grey card. It's lit from
the side, to show some texture, so you end up with 3 stops of DR coming
off the card. Lets's also assume that you expose to the right, so those
three stops are represented by the three MSBs.
At ISO 100, your data will vary in range from 0x200 to 0xFFF. However,
at ISO 12800 your data will vary from 0x001 to 0xFFF, so you will have
all 12 bits of data to express those three stops of light.
I might be making some critical mistakes involving noise floor, or just
from not looking at the difference in the numbers of photons represented
by a least significant bit. However, there is a good chance there there
is someone on this list who is nerdy enough to have already worked out
the math.
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