Hi.
I have a shoot coming up next Saturday and I`ll be using the C300 and Canon L series 28- 300 lens. Does anyone know how much strain you can put on the EF mount on the camera? Would I need a support system for this lens?

I regularly use the 70-200 and canon's cinema primes on the camera with no support all the time. These are a little less than a pound lighter than the 28-300. If you are worried about damaging the mount, I don't think that's a problem the ef mount is designed to support lenses heavier than this (for still camera purposes). If you are worried about stability, and you should be, then a rod-mounted support is probably recommended.

I have shot with EF 70-200 f2.8 L IS II USM lens mated with EF 2xII TC and used it without any rigs. Also have used the EF 100-400 lens. Those are similar weights and so the EF 28-300 lens won't be a problem.

Hi Barry and Sabyasachi.
Thank you both for your replies. As a documentarian I like to travel as light as possible with as little extra weight as possible, so this is encouraging.