Testing my GH2's sensor

Started Feb 20, 2011 | Discussions thread
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bg2b OP
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Re: real ISO comparsion from RAW
In reply to compositor20, Feb 22, 2011

That's a good point. Here's a contrived example using dcraw to do the push and conversion, where I know what it's doing under the hood.

About the same in the shadows, with an obvious difference in the highlights. But when I tried to do the same thing in Lightroom, I found it wasn't just a matter of moving the exposure slider to +2. There were hue shifts and other effects. Working a bit got them close, but it's wasn't a simple matter. Unless one can develop some sort of methodology or preset to match the higher ISO easily, it may well be better in practice to just live with the loss of highlights.

I also looked a little more closely at the RAW histograms in the two cases. 2500 is not quite the obvious 4x multiplication of 640 that I expected. There are a few additional unexplained gaps in the histogram, and the overall envelope looks a bit smoother than I would have expected (RAW noise reduction maybe?) Who knows what the heck is really going on...

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