Re: [Openexr-devel] f-stops and steps. How are they related?

[Yves Poissant]

Sorry about my previous answer. It was too quick. I answered without 
actually testing.

The actual pixel value where the 50% pattern is of similar intensity is 174. 
So it gives me a gamma of 1.8.

I now remember that I once set the gamma to 2.2 for a work I had to do but 
after a while I found it way too dark for my taste and lowered it to 1.8. 
This is where I feel my visual perception of the regularity of a ramp is the 
most uniform. But my confortable level when I work on photographs is 
actually 1.3.

Yves Poissant
Hash Inc.

> If you care, you can estimate the total gamma of your setup with a series
> of test images.  Create an 8-bit image with the following pixel pattern:
>
>     BBBBBBBBBBGGGGGGGGGG
>     WWWWWWWWWWGGGGGGGGGG
>     BBBBBBBBBBGGGGGGGGGG
>     WWWWWWWWWWGGGGGGGGGG
>     BBBBBBBBBBGGGGGGGGGG
>     WWWWWWWWWWGGGGGGGGGG
>     BBBBBBBBBBGGGGGGGGGG
>     WWWWWWWWWWGGGGGGGGGG
>     BBBBBBBBBBGGGGGGGGGG
>     WWWWWWWWWWGGGGGGGGGG
>     BBBBBBBBBBGGGGGGGGGG
>     WWWWWWWWWWGGGGGGGGGG
or
>     gamma = log (0.5) / log (v/255)