I used to have the 400/4 and the 2x and shake was bad without the mirror locked
on my old Manfrotto 075/029 combo and horziontal shake was visible with mirror
lock.
I'd expect an 800mm setup to be difficult to use, especially when you're effectively at f/8 wide-open. I've heard you really need to use two tripods when using the 600mm or 800mm f/4 lenses.
Despite people bagging the 055 tripod I've had mine with the 6x7 in "portrait" orientation with the 300mm f/4 lens attached, shooting at 1/60th with MLU, with no problems.
And a pretty common "little" problem is that the chain breaks in the assembly
that couples the aperture to the metered prism.
I seem to recall that that can happen when you a change metered prism without taking the lens off first. The prism coupling appears to be designed to cope though... maybe its just not entirely reliable.
I keep forgetting that my 67 needs to be looked at... 1/500 and 1/1000 shutter speeds are acting up.
Cheers,
- Dave
http://www.digistar.com/~dmann/
