I have too.
There is a big jump in price, the 400 Do would be perfect if its image quality was better than the 100-400mm for its weight and size.
Im guessing the 500mm F4 II is the most popular for birding? being longer than 400 and nearly a KG less? and more than F2.8 is needed for wildlife for decent DOF?
Ive been doing the same and with the high ISO capabilities of the 5DMKIII justifying at the cheapest £6000 more than the 400 F5.6 when its IQ is stellar and comparable to the other big whites although a few stop slower, no IS and its weight is 1/3 any of the big whites. IS isn't necessary when shooting at such high shutter speeds but its nice to steady the viewfinder!!
If only they made one with IS…. It would be perfect.
I went to the Farne islands this weekend and there were plenty of guys with the big whites but they were laden with massive tripods with gimbal heads and looked nakard! Just seems a pain in the ass to shoot with, difficult to track as the closer the birds came overhead you and the camera body need to go really low almost crouching on the ground while attached to a tripod and your just not free when using tripod.
After having my 40D and battery grip with 24-105mm and 5DMKIII with 70-200mm II and 2x extender strapped to my shoulders and my bag on all day with 8 hours of shooting my arms were tired. Im 26 and a pretty fit strong guy so I hate to think what they were like carrying the big lenses and tripod all day.
Another issue I saw was where we were was very close to the cliffs and about a foot over the fence was a huge drop. The cliffs weren't particularly flat obviously and the guys were having trouble getting the tripods stable enough to shoot, then when the light changed and they needed to move position it was like a mass migration, there was me just laughing away to myself.
Also while on the boat the lenses were too big for them to quickly get the lens set up and shoot where as the guys with the 100-400, 70-200mm with extenders, 70-300mm, 400 and 300mm primes managed to get up and shooting really quickly, so there are pretty big positives to being mobile.
Another question is how come they can make a really nice compact 300mm F4 IS and not a 400mm F4 IS that isn't DO, I suppose the reason is it would be smaller cheaper lighter and make the 2.8s less attractive?
Obviously I would love one, a 300 F2.8 400 F2.8 or a 500 F4 who wouldn't but there has to be some kind of balance between weight, usability, size and price. Which keeps bringing me back round to the 400 F5.6…
I think the 200-400mm would be my perfect lens is the best of both worlds but its still 3620g and massive!
It makes me wonder even more when I was shooting with the 70-200mm F2.8 II with just a MKII 2x extender and the IQ I've been very surprised with, I wasn't expecting brilliant results but they really are pretty good… The AF did hunt a little but was still pretty impressive with the 5DMKIII.
This is a 100% crop from that combo.Puffin, Farne Islands, Seahouses
, on Flickr
5DMKIII 70-200mm F2.8 IS II 2x extender MKII, F7.1, 1/2000, ISO 640
Obviously I don't really have any experience with the big whites so these are just observations of one trip. So any thoughts are most welcome