The process is rotate a clip, export it with the filter applied, bring it back into Shotcut. The idea is to avoid the overhead of continuously applying the rotation. The surprise is in the exported file: much of the contrast is lost.
Original (Yes, it’s overexposed)
The processed image (screenshot in Linux Shotcut - 16.11.02) was written using DNxHD (atsc_1080p_2997).
Looking at a histogram of the exported file, everything is shifted to the right (white side), leaving a straight line (no brightness) on the left (black) side. Tweaking contrast and brightness doesn’t restore the full range, of course. (BTW, does Shotcut have a histogram capability? I had to use Resolve to inspect the original and exported files)
What’s happening here?