"Chris B" <c_b### [at] btconnectcomnospam> wrote:
> I don't know of any way of measuring the light that would be recorded by the
> camera during the render.
> However, once you have the rendered bitmap you could read the values for
> each pixel and average them, which would give you an approximation of the
> amount of light that the camera captured.
>
> You could probably do this post-rendering step using POV-Ray, by defining
> the image as a pigment and using the eval_pigment function to find the
> values of each pixel. You could then display the total or average value in
> the message stream or you could use the value on a second pass at rendering
> the scene (e.g. turn on another light if the first pass was too dull).
>
> Regards,
> Chris B.

This may be the best approach, however, the resulting image will be
low-dynamic range, i.e., values greater than 1 will be clipped, giving you
a false result.  Perhaps use this approach, but using HDR image
output/input feature of megaPOV.  (I do something along the lines of this
somewhat successfully for the HDRI environment lighting macro I've been
working on for a while.)

-tgq

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