Prime / 100-400 Sharpness ??

Am I expecting too much from 300mm & 400mm primes, shouldn't they be sharper than my 100-400.

Not completely satisfied with my 100-400 for BIF shots I've been trying a few different primes and I just can't find one to be sharper than my 1-4. I think I have a very sharp copy for still shots but it's not great for flight shots, my shutter speeds are usually 1/1000 to 1/2000. I've tried the 300f4 IS, 300F4 non-is, and 2 new 400 5.6's. In controlled tests with the 300 non is and the 400 5.6's I find them to be identical or very slightly less sharp then my 1-4, all things being equal. These have all been compared shooting off a sturdy tripod, mirror lock-up, remote, and reasonably fast shutter speeds ext.... All lenses have also been micro adjusted on my 50D.

In the real world I shot some BIF with the 400 5.6 and was happy with the results but not convinced that it wasn't anything that the 100-400 couldn't do. There still were a fair amount of times when the focus point was on the bird but it still wasn't in good focus, yes AI servo and center point only.

So can I expect the 400 5.6 to be that much better focusing in the long run ? I find it really hard to see a difference in focus speed by panning around in AI servo and comparing the two. Is there a better way to measure focus speed ?

Just not sure if I should keep the 400 5.6.

An example might help. You say not quite in focus (wasn't in good focus.) Are we discussing the area of the limits of AF at finding the bird's eyes? Have you ever tired MF for BIF? Myself, I have seen a distinct difference between the results when using a 100-400 vs the 400/5.6 - 400/5.6 wins.

I get some flight shots that are way out of focus and some are just very soft and in both cases the background is way OFF so I know the camera didn't miss the bird totally, maybe it was in the process of re-focusing.

Only ever tried MF a few times with a TC, got a few decent ones but it was tough.

Ok, Here's two 100% crops I took today. Which one looks sharper, or about the same ? Everything set to 0 in processing.

Not that it's a problem but, I noticed that the 400 5.6 meters and exposes 1/3 stop under what the 100-400 does and when shooting the white focus chart the white area has a purple tint to it, I guess from being underexpposed ?? you can even see a slight color difference in the crops below even though both were shot at the same exposure with the flash.

i'll just say this........@ 400mm you'll have a hard time finding anything significantly sharper than the 100-400L ... in fact i have given up .

ed rader

second one look sharper

Diver-Down wrote in post #7851607
Ok, Here's two 100% crops I took today. Which one looks sharper, or about the same ? Everything set to 0 in processing.

Not that it's a problem but, I noticed that the 400 5.6 meters and exposes 1/3 stop under what the 100-400 does and when shooting the white focus chart the white area has a purple tint to it, I guess from being underexpposed ?? you can even see a slight color difference in the crops below even though both were shot at the same exposure with the flash.

I'd say shot #1 is a tiny bit more sharp and has more contrast than #2 for my untrained eyes.

ed rader wrote in post #7851643
i'll just say this........@ 400mm you'll have a hard time finding anything significantly sharper than the 100-400L ... in fact i have given up .

ed rader

Yea, that's about where I'm at. Even the 300 primes I tried weren't any better than the 100-400 at 300, actually the one was you re's.

The 100-400 just seems to have trouble tracking birds and I was hoping the 400 would do better at that, which it may but it's hard to tell for sure from my one shoot and my season for BIF is about over.

I think the first one is a bit sharper...but not significantly. Based only on this it's hard to argue in favor of the prime.

the 400 prime wins for birding by quite a bit as far as im concerned.

morehtml wrote in post #7851994
the 400 prime wins for birding by quite a bit as far as im concerned.

I'll second that. I owned both the 1-4 and the 400 prime and the differences in my keepers and sharpness between the 2 was like night and day. I doubt I'll ever consider owning the 1-4 again unless they do a major upgrade to the lens and focus motor.

I have also been going round and round with the same dilemma. I have been considering buying the 300mm F2.8 or the F4, but some have given me the advice to stay with the 100-400. It sure is nice to have the versatility of the zoom. If the tracking and sharpness is that much better I will switch. These were all taken with the 100-400. Do we just have a great copy?

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On your crops these were either taken at different distances or the 400mm of the prime vs the zoom is a different true mm and this makes them hard to compare. The 1st shot has a obvious closer distance advantage and will show more detail

Heh - I think in a roundabout way, you guys helped me decide to keep my 120-300...Maybe?

morehtml wrote in post #7852139
On your crops these were either taken at different distances or the 400mm of the prime vs the zoom is a different true mm and this makes them hard to compare. The 1st shot has a obvious closer distance advantage and will show more detail

Yes I noticed that too, and the first shot is the 400 prime. The crops are identical at 903 X 722 and I am 99% sure that the tripod didn't move between shots.