How do you read the FRV histogram?

Dear Sir:

Let's try to approach things step by step.

> The leftmost mark of the scale is the level that corresponds to the value of “1” in the RAW data.

The leftmost mark is the left wall; it is where the value in raw is equal to 1.

> The histogram step on the horizontal axis is 0.1EV, so there will always be a “comb” in the shadows, as there are less possible levels than 10 levels per stop.

In raw, say it is 14-bit raw, there are maximum 16383 levels from shadows to highlights. The first stop in highlights contains half of those, up to 8191; next stop contains half of what is in the first stop, 4095; following stops contain respectively 2047, 1023, 511, ..., and finally, the last three stops contain 7, 3, 1 level respectively. This progression simply means that the exposure in each next stop is half of what it is in the previous, brighter, stop. If the step is 0.1 EV, to fill a stop one needs at least 10 levels; with only 7 levels you will see gaps, and histogram starts to look as a comb.

If something in the above is unclear, please say so and we will try to explain better.

I also dont understand a about your histogram perhaps there is some background information needed before one can understand it.
What is "16383 levels", levels of what what exactly could you refer to somewhere where it explains in layman terms, i am consumer and dont need to dive deeply in the inner working of how data stored in RAW file.

"from shadows to highlights" shadows and highlights are not the edges of traditional histogram its in the middle edges represented by blacks (left most wall value 1) & whites (right most wall value 255).

"first stop in highlights contains half of those, up to 8191" from what i understand so far from manual "EV0 – the level that corresponds to the middle gray" so first step in highlights would be from EV0 to +1 EV on your histogram?
By the way your histogram does not show +1 EV it goes from EV0 to +3 EV.
"Next stop contains half of what is in the first stop, 4095; following stops contain respectively 2047, 1023, 511" wait there are only +3EV on your histogram so did you actually mean -1EV, -2EV -3EV etc. until we reach the "left most wall" of your histogram?
"This progression simply means that the exposure in each next stop is half of what it is in the previous, brighter, stop." Each next stop is counting from EV0 down or +3EV down or from "right most wall" of your histogram?

"If the step is 0.1 EV, to fill a stop one needs at least 10 levels; with only 7 levels you will see gaps" wait step is 0.1EV where on histogram i so far dont see even 1EV steps its -10 -5 0 and +3, where 0.1EV come from?

Could you demonstrate screenshot of how overexposed image would look on your histogram, does it anything that reaches past +3EV mark or past "right most wall"?

Yeah just what exactly "right most wall" on your histogram represents?

By the way i watched the video about RawDigger histogram, guess it has similar histogram, and still i have zero clue what it all means. Is there name for this particular histogram so i can google more info about it?

Is there possibility you include RGB histogram for simple folks who dont need to dig in, sort of same histogram as shown when you switch to embedded JPEG ("J" key) and it seems close enough to RGB diagram that shows in Photoshop.

 
 
 

For me i learned that overexposure is shown when the lines hit the right most edge of histogram and (similar to regular histogram) and its enough for me, rest not really concerns me at this point.
Also i find myself using Exposure Stats window more than i use histogram, because it actually shows how much percentage of overexposure is in each RGB channel. "OE+Corr" just means after you applied the exposure adjustment inside FRV, it can be pretty much be ignored also.

This are exposure stats i mentioned in previous post

Inside FRV histogram has 15 stops total, -12EV is left most border of histogram, +3EV is right most stop of histogram.
This setting
is for Exposure Stats meaning after how many EV stops down from over exposed mark (+3EV) program will report under exposed pixels (on histogam in my previous post that spot marked with "UE -10").
Theoretically this gives idea that my camera has total 13 stops of usable dynamic range everything lower is just clipped shadows, however its only for photos taken on ISO 100, on higher ISO values clipping occurs much faster i think at ISO 3200 all you get is about one EV stop of dynamic range, i would not trust it too much for shots with high ISO (Of course author made adjustment for this as well in options "ISO-Based underexposure limit", but i have not played with this yet)