Comparing object to background radiance

Hi,

**edit

I’m interested in quantifying the chromatic and luminance contrast of an object’s radiance against the radiance of an open background (i.e. looking horizontally underwater) for a given visual system. What would be the most appropriate pipeline in the toolbox to follow for this?

Also, can a high reflectance substance, such as a board of barium sulphate paint (illuminated by the same natural light as the object) be used as a substitute for the background?

Mark