NancyP said:
I have been curious about this lens for a while - still haven't bought a Big White, still using my "toy lens" 400 f/5.6L, now wondering if I should break down and get the 500II.
Even with the diffractive optic formula, a 600mm f/4 is going to be
big, and while DO keeps the outside size down a little, it doesn't particularly help with the weight.
Going from the 400mm f/5.6 to the 500mm f/4 is already quite a jump in handling. Going up again to 600mm f/4 DO
should be, if the other DO lenses are anything to go by, at least another +30% weight and +20% size over the 500mm, if not more.
As someone who uses the "big whites" often for work but also still keeps the 400mm f/5.6 to hand for hobby shooting, I feel it's important to stress that these lenses aren't a flat, linear upgrade path. It's not as simple as 600 4 > 500 4 > 400 5.6 and none of them are a replacement for the other. If the 500mm is the one you've been wanting, stick with getting the 500. Wanting the 500 but buying a 600 is like wanting a 50mm but buying an 85; it's that kind of jump in framing, as well as size.
Wait and get the 600mm if you shoot from a tripod already. That jump in bulk and the significantly higher difficulty in framing anything which isn't perfectly motionless won't matter on a tripod, so sure, go for the biggest. Also go for the 600mm if you want to always have the tightest framing and flattest perspective possible; 500 to 600 may only be 100mm on paper but in practice it feels like you're working with two thirds the view.
Get the 500mm if you want to be able to shoot handheld, even if only occasionally. Doesn't matter how big and strong you may be, 600mm wears you down quickly; 500mm is
far easier. It's also easier to transport, and a DO version of the 600mm is unlikely to change that distinction. The field of view is also much better if you need any kind of versatility. For what it's worth, BBC production keeps many copies of the 500mm f/4L IS II on hand, but only two 600mm f/4s are kept in-house and if more are needed they're rented, purely because the 500mm framing is so much more useful for broadcast.
Keep hold of the 400mm 5.6 regardless of what else you buy, 'cause I promise you, even if you had the 600m f/4 DO, 500mm f/4 II, 400mm f/4 DO,
and the 200-400, there will still be times where you'll be very thankful for the ease of the 400 5.6.