DxOMark's measured ISOs vs. manufacturer ISOs

Started Mar 13, 2013 | Discussions thread
edhannon
edhannon Senior Member • Posts: 1,761
ISO vs "pushing"

Gordan, your reply got me to thinking about ISO and digital.  In particular, the question of whether, when faced with a low light situation, if 'tis best to change ISO or to do like we did in the film days - expose as though we had higher ISO in the camera and push develop?

I have never been really satisfied with the testing to answer this.  Concerned that too many variables changed between the two comparison images - noise reduction, ettc.

So for my question: would it make sense to measure this way:

1. Create a tone curve for at the base ISO by taking a succesion of images of a grey card at varying exposures and plotting the result. I still have my program that plots this from the origianl raw files. It also identifies the the SNR 0 point.

2. Create another tone curve at a higher ISO (say 800)

3. Compare number of stops from metered grey to SNR of 0 for both. Subtract the number of stops difference between ISO 100 and 800 (3 stops) from the base ISO one

If the higher ISO has more stops than the adjusted base ISO then increasing the ISO is best.  If the adjusted base has more stops then "push" developing in Lightroom/ACR is best.  If they are about the same do what ever is easier.

Comments?

Ed Hannon
http://www.pbase.com/edhannon

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