There's a shadow around the scrubber thumb that seems somewhat strange to me. (Contrast-stretched screenshot attached.) I think this is there to give a 3D effect to the bar under the thumb (the shadow, well, makes the bar look like it bends under the thumb), but the shadow on the flat gray surface of the control bar seems off. Not sure what a good fix is here... Mask the shadow to just the horizontal region over the bar? Add the shadow/gradient to the bar itself?

I think the radius of the spread is just too large. The play, full-screen, and volume buttons lack a shadow, so I think the intent here was just to put a shadow on the thumb itself.

(In reply to Justin Dolske [:Dolske] from comment #0) > Created attachment 8813440 [details] > screenshot.png Thanks for pointing this issue out. That's seems strange to me either, I didn't notice the spread is that apparent when control bar shows over light background video. (In reply to Jared Wein [:jaws] (please needinfo? me) from comment #1) > I think the radius of the spread is just too large. The play, full-screen, > and volume buttons lack a shadow, so I think the intent here was just to put > a shadow on the thumb itself. Yes, another intent was to make a distinction between thumb and progress bar, and blur the joint. I'll shrink the size of spread(attach a screenshot later) and see if it make sense to everyone. Thanks.

The radius of spread is shrunk from 5px to 2px, and the shadow is still visible between thumb and progress bar. Could you give me feedback about this fix? Thanks.

Comment on attachment 8814787 [details] Screenshot-shrunk-spread. Looks better to me, thanks!

Comment on attachment 8814787 [details] Screenshot-shrunk-spread. Much better!

Comment on attachment 8818492 [details] Bug 1319587 - shrink radius length of video control thumb spread. https://reviewboard.mozilla.org/r/98556/#review98952

Pushed by jwein@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/bc26b2f7b6e7 shrink radius length of video control thumb spread. r=jaws

Pushed by jwein@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/afe3fed7c351 shrink radius length of video control thumb spread. r=jaws

Tested this issue on Windows 10 x64, Ubuntu 16.04 x64 and Mac OS X 10.11 on Firefox Nightly 53.0a1 and I confirm that it's not reproducible.