Thanks :-). It's doing some quite heavy lifting for the HSB calculations. Every frame of the video is drawn onto a hidden canvas. The pixel data from that canvas is then read, manipulated and drawn onto the visible canvas. In Chrome and Opera this partially happens on the GPU which makes it quite smooth, but in Firefox it is slow to an extend that made me add the "videoOnly" mode. (In this mode it just shows the video element and only allows for cropping.

Would it be helpful if forcing the “video only mod”e would be exposed as a public method? (Currently it can only by switched off by setting the forceHSB flag to true.)

Please find the github repo for the project at https://github.com/WolframHempel/photobooth-js