Most recent issue, as said above. Reallife transparency is a volume effect, so internal reflections of reflections of ... will give

result = R (1+ T^2 / (1- (RT)^2) ) for transparency T and reflection R, with R< 1- T

while Poser transparamcy is a surface effect, with

result = R (1+ T^2 / (1-R^2) )

ans so my question was: how far is the Poser result off (too bright, as a relative percentage). I did run a pack of scenarios in Excel, and found that Poser is at most 7% off (that is: the rendered result is 7% brighter than real life) at 30% transparancy and 70% reflection. Lower reflectivity for that transparency, of deviating transparencies with their (even max) reflectivities, give less and less relative errors. For T>50% or <15%, deviation is less than 5%. For T>65% or <7% deviation is less than 3%.

I can't decide for you but I can live with that, so for me this issue is not really an issue any more.

Finally, I'd like to flag an issue on transparency. It reduces the brightness of reflections and refractions, relative to the brightness of the original reflected/ refracted object. At the end of the render process, when having gamma correction enabled, both will be corrected (brightness increased). But thanks to gamma, the intensity reduced reflection will be corrected (relatively) more than the original object.

For instance (the extreme). Transparency 30%, reflectivity takes the maximum 70%. Real life internal reflections will make it to 76,6% while Poser will present 82,3% (the just mentioned 7% up, relatively). Gamma will enhance this to even 90%.
If I want to adjust the reflectivity to cater for all of this, I have to bring it down from 70% to 50%.

Essentially (now I'm writing and thinking about it) it has nothing to do with transparency. Any reflectivity < 100% will be pumped up by gamma correction, as will any brightness reduction due to partial refraction or transparency. It's like brightness which is reduced by shadow, and so is pumped up by gamma. Now brightness is reduced by reflection (etc), and so it's pumped up as well. Photorealism anyone?

happy rendering.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

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