[Radiance-general] Pvalue for converting to luminance

[Greg Ward]

Hi Cw,

I'm not sure how pfsview converts colors to luminance values, but it  
may apply a different set of coefficients from those used in Radiance  
(and pvalue).  This could explain the discrepancy.  The best way to  
check is to compare values for a gray pixel, which should be the same  
regardless of the color -> luminance conversion.

Also, are you 100% sure you are checking the exact same pixel(s)?

-Greg

> From: "chang cw" <solomoncw76 at gmail.com>
> Date: September 5, 2008 7:27:46 PM PDT
>
> Hi all,
>
> I tried to apply the factor of 179 to the scaled brightness from
> pvalue. However, it seems that the value is still slightly off from
> the actual one read from psfview.
>
> The value from pfsview is 2.579e+4
>
> while from pvalue is 2.803e+4
>
> i used pvalue -b -o sample.hdr
>
> Is there an exact value for the scale ?
>
>
> Thanks
> Cw