You asked
Is the canon ef 85mm f 1 4l is usm good on aps c?
Yes, it works on APS-C, but it behaves like a longer lens there. On a Canon APS-C body it frames like about 136mm on full frame, and f/1.4 gives roughly the depth of field of f/2.2. You get a tight, flattering portrait view with good background blur, but you'll need more room between you and your subject than you would on full frame.
It fits these APS-C bodies, among others:
If you mostly shoot people indoors or in small rooms, a shorter lens will be more practical. The portraits guide explains the trade-off, and the sensor sizes guide shows how the crop factor changes the view.
Written by Claude from this site's pages.