Rented a 600/4 for a week

I rented a 600/4 for a week to see whether the focal length was my problem or whether I was my problem. I am, at least partly, my problem. The lens is magnificent and it also weighs a small child. I spent three mornings with it at a coastal refuge and by the fourth my left shoulder was a concern. It solved a couple of things I’d been complaining about, specifically working distance with wary raptors, and it did not magically produce sharper images of stationary birds at the same range I was already getting with my 400 plus tele-converter. I’m glad I tried it. I am not buying one.