martin_hale

This is a late post to this topic but I wasted alot of time trying to sort out a sharpness problem with my first Canon 100-400 and feel strongly about this lens.

 

In answer to the question is there a difference in sharpness between this lens and the 400 f5.6L the answer is yes there is, and it's noticeable. I've owned three (yes 3) 400 f5.6L's and two 100-400's. The second 1-4 was a replacement by Canon for the first, defective 1-4. This latter had a focussing problem, as demonstrated by the fact that I could consistently get better focused images by manual focus than by autofocus (2x EOS 3's used). The second 1-4 was lent to me by Canon as they attempted to resolve the first's problem. After running one film through this lens I knew immediately which one I was going to keep.

 

That said there is a noticeable difference (10x loupe) between the 1-4 and the prime 400. The 1-4 is very good but the 400 is just that bit better. I have got some very good (sharp) shots from the 1-4 with a 1.4 converter, but I would have to be desperate to use a 2x with this lens. I've never tried the 2x with a prime 400 (I've got a 600 IS to do this job) but if circumstances demanded it I wouldn't have a problem with it, and would expect good results.

 

The main advantage of the 1-4 to me is the closer focus than the 400 can achieve. I'm personally not a great advocate of IS on this lens. The tests I've done show that you are still better off tripod mounted. I've also latterly become suspicious about the ability of the 1-4 to do tracking shots of birds in flight (I photograph birds almost exclusively)compared to the 400. I haven't done enough flight shots to be sure but I'm going to be using the 400 for this type of shot in future.

Slightly off subject, but don't for one moment believe that the support from Kirk can't be any worse. I have a fairly new Kirk Window Mount from which a small but vital part has vibrated free and gone missing. I have both e-mailed and written to Kirk about getting a replacement part, at my expense, in order for me to fix the now useless Window Mount, but can't get any response from them. They are very fast to respond to orders for items in their product line but once they've got your money don't expect any favours.

With regard to the sharpness of the 100-400, there is, in my experience, a substantial difference between individual lenses. With my original 100-400 I could consistently produce noticeably sharper images using manual focus than when using autofocus (400mm, f5.6, tripod mounted, IS off, mirror lock, electric release, autofocus one shot or AI servo, central focusing point). There was clearly an autofocus problem and it was returned to Canon under warranty. They were unable to fix it (it was returned to me as "fixed" but if anything it was even worse)but did eventually exchange it for a demo model that they leant me whilst mine was in the workshop. This one is very sharp, even with a 1.4 converter. Under a 10x loupe it's almost if not as good as my 400mm f5.6L, which is consistently excellent. The moral of the story is that this is (or can be) a very sharp lens, but there are some lemons out there. If you are unlucky enough to get one, complain! I hope that you get the same sympathetic treatment that I did, for which my thanks go to Canon.