pre-ISO vs post-ISO (resurrection of a dead-beaten horse)

Started Oct 4, 2013 | Discussions thread
Jack Hogan Veteran Member • Posts: 6,682
Re: pre-ISO vs post-ISO (resurrection of a dead-beaten horse)

rubank wrote:

In the past I have said and demonstrated that the post-ISO routine (a k a "ISO-less") doesn´t yield as good results as pre-ISO (ISO set on camera) on the Nikon D800. E.g ISO 100 underexposed and pushed in post vs same exp at ISO 3200 with regard to shadow noise and colour. (I have never denied that you get higher DR at low ISO, but that wasn´t the issue here; not every scene needs high DR capture...)

Hi rubank,

I believe that nobody is disputing that ISO100 vs a higher ISO captured at the same exposure with a D800/e will result in a cleaner image up to about ISO1600*. It's obvious because the read noise goes down as analog gain/ISO is raised

Read noise estimates should be accurate to a few tenths of an e-

and because people who have analyzed the sensor have quantified that the shadow SNR improvement should be about 0.4 stops for a 4-stop increase in ISO from 100 to 1600. So no argument there.

Some people, like me, are on the other hand curious to see the alleged sensor-induced effect on color of said ISO change. Sensor induced, not software induced.  It could well be there (a non linearity worth investigating perhaps?), but since some of these very same curious people are not the fortunate owners of such fine a tool, they are left to wonder if anybody will produce a pair of NEFs through which this issue might be checked out.

All we need is for someone to make available for download two NEFs of a high DR scene, captured with decent technique on a tripod. The first, manually 'properly' exposed at ISO1600; the second captured immediately after at ISO100, all other things being equal.


*no point going above that, as you by now know

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