500mm vs 600mm?

BirdShooter7 wrote:

While lighter weight and shorter length would be welcome in a 600mm f/4 DO I don't imagine the diameter of the lens will be any different from the current 600mm f4 and I expect the price to be quite high. Also though the 400 DO II is way better than the original optically I'm not 100% convinced that the DO technology is quite up to the conventional designs though it is getting closer. I have a feeling the rumored 600 DO wouldn't be a real option for me.

There are definitely some subtle compromises with DO. While the 400/4DO II is an excellent, cutting-edge lens in many ways, it handles things like small points of specular light, or sunlight coming through tiny leaf apertures in trees very poorly in terms of onion bokeh. Sometimes it doesn't, though, so I think it has something to do with wavelength composition. I think it also affects AF in marginal conditions, which would explain why cameras that support multiple f/8 AF points with the 100-400 II only support center point with the 400/4DO II.

That's the main negative thing that weighs in my mind about having the DO II; the fear that the 7D3 or whatever turns out to be the logical successor of the 7D2 only supports center-point with the lens at f/8. That will make my heart sink. Even 9-point in the center is much less hunting-prone, and quickly locks onto something close, even if you have to tap again or manually override, which is much faster than having the lens slowly go way out of focus, while your subject eludes you. F/8 AF on the 7D2 is there in the center, nominally, but it sucks unless light and contrast are good, and depth is simple.

As far as 600/4DO goes, I can't imagine that weighing less than 8 pounds, and still a tripod lens, basically.