I'm going though Michael Freeman's books on exposure. I'll take his example of a light skin portrait to illustrate my question, although there is nothing specific to that kind of pictures. The author states:
The average brightness for this kind of Caucasian skin needs to be between 60% and 70%, around 1 stop brighter than an average reading.
Being familiar with the way metering works, my understanding is that at exposure time, metering for the skin and correcting at around 1 stop over the metered value will achieve this result.
Now, let's assume that I'm a newbie who still frequently messes his exposure (hum). I have a badly exposed portrait in Lightroom, and need to fix the exposure level appropriately: how, preferably in Lightroom, can I measure the relative brightness of the skin to know I've reached 60% - 70%? Said otherwise: can I measure a point to know where in the histogram it falls?
PS: I know people will be tempted to answer that I should simply know when the skin is correctly exposed, but truth is I really don't :-( So I would really like to be helped by actual measurement.