Hi,

I wonder what is the real effect of this button :

Is it sharpening the rendered video (as indicated in the name ?) or making it softer (I can read message "apply a blur mask for output sequence" when my pointer pass over the button) ?

It says that "unsharp masking" is being applied, despite the name it's a common sharpening technology, see: https://en.wikipedia.org/wiki/Unsharp_masking

So yes, it will sharpen the output video. I leave it on all the time.