There are techniques to extract some detail in the areas burned out by overexposure(I read about it in the book of Alexis Van Hurkmann: "Color Correction Handbook", section: "Dealing with overexposure"). These techniques take advantage of “superwhite,” that is, values above the “reference white” (or white point) value. I, for years, have assumed that superwhite is above 1.0. In fact, in videoscopes, values as high as 110% can be seen. I went back and read poynton's book (https://wangwei1237.github.io/shares/Digital_Video_and_HD_Algorithms_and_Int...) and I found that actually superwhite is only mentioned in reference to the limited range (mpeg, 16-235) and not the full range (jpeg, 0-255). It is mentioned in the “swing study” section on page 42 and also in the “Processing coding” section on page 45. Basically, my mistake is assuming reference white at 235 to be the same as reference white at 255 and corresponding to 1.0. Instead, apparently, even if you have limited range values above 1.0 they are still within the 0-1.0 range of the full range, and thus are still “legal” values. I'm sorry, I have bothered you for a long time about something wrong.... There are still many things I don't understand in the color pipeline, but I'll stop here.