Yesterday Mark mentioned maybe usingto the right. I had heard of this before, but never really considered it. I read up on it. I liked that it might provide more detail and less noise, and did some experiments this morning. My 600D seems to cope with 2, maybe 2 1/3, to the right.
However, there's always a compromise. My big zoom, at 500/600mm allows me f/6.3 max . Using ETTR means that, at any given , I am slowing down the . Shooting handheld, as I often do, even with the great optical stabilisation the has, I really don't want to get too slow on the - or else motion blur is bound to occur. So, either I increase the (and noise), or miss shots due to blur.
Now, in practice, I am finding I can shoot OK, at 1/200th second , at 600mm, with OS switched on, stationary subject, but not much slower. On a typical fine morning, with the subject in the shade in the bush, this means using 1600 or more (and my camera gets a bit noisy at these higher ISOs). To get the back to 800 or less, and keeping above my minimum , means forgoing ETTR.
I am not complaining, I knew this was the shortcoming of the f/6.3 limit on the . Maybe ETTR is something for use only (for me).