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 p.2 #9 · My X-E1 vs D7100 High ISO comps | |
aleksanderpolo wrote:
P.S. One thing that is interesting to me is why there is such a big difference in underexposing at base ISO and pushing (or pulling?) in LR vs high ISO for D7100. To my untrained mind they are both amplifying signal, one in camera and one in computer?
‘I think’ this is a lot complicated than it looks. And really case by case not only depend on camera sensor but also depend on particular picture.
ISO is amplifier in analog domain, Push after capture in raw convertor is in digital domain. High ISO is the gain of amplifier usually maximize the signal, but will degrade Signal to Noise ratio because itself introduce noise as well, maximized signal can utilize more bit in Digital later for process. However, High ISO, not only amplifier signal, but also noise. Once this amplified noise plus noise of amplifier itself more than LSB(smallest step) in digital, you will see noise performance be worse, as you keep feed ADC ‘bad’ signal.
Once the signal through ADC, in digital domain, we no longer improve or degrade SNR.
In most online samples, We focus ourselves in dark area of photo, thus, after certain ISO point, we warrant ourselves see worse performance like Banding, Blotchy….
So, as a guide line, after certain ISO for certain camera, you will not see benefit of push ISO. thus ISO25600, or ISO 128000000 is really market BS with no real meaning other than review your image.
However, in real word, there is possibility that depend on your scene, high key, low key, noise character, or your subject matter, you might still benefit with push ISO than push afterward in RAW. That way you utilized most bits in your digital architecture. With advanced process power of raw converter like noise reduction, tonality mapping, you might get better results.
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