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Re: Dynamic Range Really isn't as important as you are lead to believe.
In reply to _sem_,
5 months ago
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_sem_ wrote:
Anders W wrote:
Yes, zero corresponds to complete darkness (i.e., complete lack of photons hitting the sensor during the exposure). If I shoot my E-M5 with the lens cap or body cap on (at 1/4000 to be on the safe side), the average ADU is equal to the value of the black-level offset.
In your example with the blue sky, R and G wouldn't be zero, merely as close to zero as to be practically indistinguishable from zero. If you merged a lot of shots of the kind you describe, you would eventually be able to distinguish the non-zero R and G signals.
The existence of an absolute zero-point, as we have in this case, is not clipping.
I'm not talking about the existence of absolute zero point and I'm not shooting wide-DR scenes with the lens cap on (except for dark frames now and then). My blue sky example is not blue sky research, it is a real-life case relevant to this thread. Certainly, with a lot of shots one would gather a few photons to get a non-zero value for those R and G. Mostly I have only one shot, which may show obvious signs of blown shadows if I push them hard enough. If I had a camera with two more stops DR they might not have been blown, and would be cleaner and more colourful too. They would surely not be blown if I added a second (long enough) exposure for the shadows and went HDR, but I rarely bother to bracket exposures.
You were talking about clipping at the black end. I pointed out that there is no clipping at that end, merely an absolute zero point, and talked about black-frame shots and your example with the blue sky to that end.
There are all sorts of practical problems associated with getting good rendering close to the black end. But they are not caused by clipping the signal above the point corresponding to true black (complete lack of photons hitting the sensor). And whether or not things are clipped at the black end was the point we were discussing all along, remember?
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