bug found in 21.5 as well as in all other beta versions:
Same auto histogram adjustment (auto mode for all channels) set to 3 channel view show different result in docked and in floating windows:
Seems like it is something related to file size and grain structure of the image. When i scale large file to 50% and repeat auto mode for all channels, i see less difference between docked and in floating windows. Very strange problem...
Also if switch to single channel view mode, the clipping numbers are the same in docked and in floating windows, but histograms show different clipping amount. It is also strange that histogram shape itself look different between docked and in floating windows.
Try to apply "auto mode for all channels" to this image: https://www.dropbox.com/s/46qr7wn3fui28 ... 2.jpg?dl=0
(this is not a film scan, but a scan of 10x15 printed photo taken with very simple Epson flatbed scanner)
Apply auto mode for all channels in floating window, press OK.
Switch to docked window, apply again "auto mode for all channels" and see the difference in histogram.
Switch back to floating window, apply "auto mode for all channels" and see the difference again.
Problem is not depends of bit depth. (same result with 8, 16 or 32 bit)
Problem is not depends of ICC profile (same result with sRGB as well as with different wide gamut color spaces with L gamma curve)
Problem depends of image size. If i reduce size to 25%, difference between docked and floating windows became less visible.