Higher ISO or underexpose then corrected in PP?

Started Mar 24, 2012 | Discussions thread
Luke Kaven Veteran Member • Posts: 5,705
Re: Higher ISO or underexpose then corrected in PP?

ejmartin wrote:

Luke Kaven wrote:

ejmartin wrote:

JosephD05 wrote:

This is a great question I was wondering the same thing. Say with a d800 and 6400 ISP or choose 1600 ISO then fix in pp

If your raw converter does an accurate job of exposure compensation, then 1600 pushed two stops in the raw converter will be as good as 6400, except that you will have two more stops of highlight headroom. There are very few cameras that benefit from an ISO more than 1600, such that a higher ISO slightly reduces the apparent noise. More typically, beyond this point, it's the low exposure that results in the noisy appearance, not the amount of ISO gain being applied.

I've been puzzled by some of the findings on the D800 in regards to this. Looking at Bill's DR Shadow Improvement chart, it shows the D800 improving in shadow response up to ISO6400.

But then it's also been suggested that the analog gain leaves off around ISO1000. Surely digital multiplication alone would not produce an increase in shadow DR in the range above ISO1000. Yet I've never heard of noise reduction being suggested as a factor until after ISO6400. I've heard the suggestion of "gain sharing" but not seen that idea advanced conclusively. Still puzzled over how this one actually works.

It may be related to this series of posts by Marianne Oelund (I presume she hasn't had the opportunity to test the D800 yet in this regard):

http://forums.dpreview.com/forums/read.asp?forum=1021&message=40947206
http://forums.dpreview.com/forums/read.asp?forum=1021&message=40951078
http://forums.dpreview.com/forums/read.asp?forum=1021&message=40952347

I don't think this relates to HPS, but to the range of ISO1000-3200 give or take. I would have expected to see HPS only much higher up. See also Bill's reply. Or have a missed something more obvious?

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