[Radiance-general] hdrgen rsp coefficients

[Gregory J. Ward]

Hi Axel,

Your interpretation of the coefficients is correct, but the [0-255]  
values are converted to a [0-1] range being put into the  
polynomials.  This would account for your odd results.

-Greg

> From: "Axel Jacobs" <a.jacobs at londonmet.ac.uk>
> Date: April 26, 2006 8:00:54 AM PDT
>
> Hi Greg, hi everyone else,
>
> This is an example of an rsp file (Optio 430):
> 3 1.44593 -0.999398 0.575389 -0.0219197
> 3 1.23165 -0.639997 0.413386 -0.00504164
> 3 1.07103 -0.436035 0.351256 0.0137438
>
> Is it correct to assume that the 1st coefficient is the highest one  
> (3rd
> order in this case), so would the formula be (for Red channel):
>
> 'PENTAX Optio 430 '
> 1.44593*x**3 + -0.999398*x**2 + 0.575389*x + -0.0219197
>
> If so, then this is a plot for some cams I've created with gnuplot  
> (again
> Red only):
> http://luminance.londonmet.ac.uk/pickup/rsp_gnuplot.png
>
> If plotted for x [0:255], that would give a dynamic range of 7 log  
> units
> for one photograph. Seem a bit excessive. Am I missing some important
> detail here?
>
> Cheers
>
> Axel