Quote Originally Posted by nouveau1 View Post
1/ what are the advantages/disadvantages to manipulating exposure using the raw luminance histogram vs the RGB one?
The raw luminance histogram allows you to manipulate the dynamic range of the image (compare it to the "levels" tool in other software) - it mainly allows you to set black and white point. There is no gamma manipulation possible, but you can do some contrast adjustments. Note that this histogram is not linear, it is logarithmic!

You ask about exposure - always adjust that in the raw luminance tool because that allows editing at the full dynamic range.

The RGB histogram takes the output of the RAW processing step and manipulates that in terms of output range. It works more like the curves tool in other software.