Wouldn't it be nice if that value simply reflects under & over exposure amounts at the current Tv, Av, Sv, NDfilter, and EvAdjust settings?
Based on the the values I saw, I don't think this is the case. I'd guess it's more like a lower level representation of sensor gain, but that's pretty much a wag.
There's a lot of strings referencing CDSGain that might provide clues. There is a function SetCDSGainStep which prints a string "SetCDSGainApex %d" which might hint at a conversion.
get_current_exp fills an array of 16 bit values: Av, Tv, "Gain", something from "ImgPixel.c", the ND value (ND + Iris cams only) and one more value that's (often?) hardcoded to 0.
For interactive testing with chdkptp, it's easier to call the functions directly with call_func_ptr so you don't have to deal with allocating memory for the array.
edit:
Split this to a new topic. The only connection to the ND project was that it was a useful path to finding the current ND value.
