You asked

Is the canon ef 135mm f 2l usm good for portraits?

Yes, it's a strong pick for portraits, as long as you have room to work. The 135mm f/2 gives tight headshots and very soft backgrounds, and you stand far enough back that faces stay in natural proportion. The portraits guide puts 135mm in the same class as 70-200mm f/2.8 for that kind of shot.

It's best on full frame. There it frames as 135mm, which is the classic portrait length. On APS-C it becomes roughly 216mm, which is very long for portraits, so you'd need a lot of space behind you. If you're shooting full frame, bodies like the Canon EOS 5D Mark IV or Canon EOS 6D Mark II are good matches. Check the lens page for the full list of compatible cameras.

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