a57 v d5100 for first DSLR

Started Apr 6, 2013 | Questions thread
Bjorn_L
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Re: Neither
In reply to peevee1, Apr 12, 2013

peevee1 wrote:

Fat Dragon wrote:

That clarifies a lot about how ISO works and affects IQ, but I'm trying to figure out exactly what you're calling BS. Do you mean that it's BS (as in disappointing) that Sony uses a system that starts the software multiplier at anything above 100, or that it's BS (as in not true) that Sony's cameras have no hardware ISO amplification?

That. Specifically these: "Your JPG would be just about black but if you bump up the RAW file, you'll get the same result as increasing the ISO because that's all the camera does."

and

" So bumping up brightness 6 stops in an ISO 100 shot will show the same noise as if you took it at ISO 6400."

I am fairly certain that is not accurate.  I believe the camera amplifies the signal coming off the sensor rather then mess around within the data-set post-capture.   Were it as you said, then there would not be so much variance between cameras in ISO performance.  Even cameras with the same sensor may select other components to be part of the sensor package (the components other then the actual sensor) these amplifiers, line-filters and so on are what differentiates the different cameras.  This is why, for example, that Nikon (and recently Pentax too) typically gets more out of a Sony sensor then Sony does.  Obviously the sensor Sony is using is just as sensitive... they would not sell off the good stuff and keep just the bottom-bin for themselves.  Obviously there are sensors with more or less sensitivity.  And amplifying a clean signal is probably a simpler affair then starting with a low quality signal.

Also in my own experiments, I have found that shooting in RAW with a d90 and d700 that I can raise the ISO some in post but that I get less noise by being closer in my initial settings in camera.  I have not done a SNR test, but I would eye-ball estimate that the noise from post is in the 1.5x as much as from in camera, maybe 2x.  I could be off by a little bit since I was not specifically checking for this but for how much headroom I had in the various RAW files.

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