SheerVideo User Manual
Ignore the Quality slider, if present. It has no effect on the compression quality of SheerVideo QuickTime movies, which is always perfect or best (Quality=Best=100).
Note: this slider was removed from the Standard Video Compression Settings dialog box in SheerVideo v2.3.8.
In the standard QuickTime user interface, the slider, when present,
is in the middle of the Compressor section of the Standard Video Compression Settings dialog box.