Sorry for hijacking the thread but can someone explain what the top attribute "cm 2 factor" does in this lens shader?
From the documentation: "In photographic mode (a non-zero film speed) this is the factor used to convert between pixel values and candela per square meter. In arbitrary mode (a zero film speed), this factor is a multiplier applied when scaling rendered pixel values to screen pixels. This is analogous to the Gain parameter of the mia_exposure_simple shader."
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