(100-400L) I'd like to check it before to buy

Started Jul 14, 2009 | Discussions thread
TwincitiesJim Regular Member • Posts: 193
Re: (100-400L) I'd like to check it before to buy

DaddyK wrote:

A couple months ago I bought a 100-400 from Samy's in LA. I didnt do any testing when i bought it assuming it would be fine. Now, a couple months later the lens seems to be brilliant at near and mid distances, but soft for longer distances. Chasing butterflies, with 400mm, it seems fine. But, birds out on the lake, or bears on the next hill (just got back from Alaska) and the image is much softer. In a couple of the longer range shots I can see that the lens is misfocused and that some other part of the image is nice and sharp. How can I test the lens to prove this to myself and Samy's? And, is it still reasonable to demand it be replaced by a working copy.




I am not sure if this is a lens problem or not. I think it is more likely a camera focus issue (or I suppose if you handhold it could be a lens IS issue). I have had the 100-400 for a little over 8 months and back in June took it on a trip to South Dakota. Everything was going fine, but then one day a fairly large number of my photos of animals that were far away were blurry (even at very high shutter speeds). I did some testing the next morning and found that when I focussed on objects very far away, my sharply focussed hit rate was reduced for some reason (This was all handheld at 400mm). That particular day the hit rate was actually very low. During the trip, I used it with both my 50D and my wife's 500D and noticed that it happens with both, but have not done testing on them to see if one is better or worse than the other. The problem I had was that I could not get it to repeat consistently. Sometime it worked fine and other times it did not. I know that my lens is very sharp when focussed well and sitting on a tripod, but sometimes I still have issues when I handhold and shoot items really far away (at or near infinity focus). I am now more sensitive to it and will adjust my focus manually if I notice it ocurring, and that seems to help some which is why I think it is more likely a focus issue. However, I am not sure because the other day when I used it on a tripod, it seemed to be better also. I do know for sure that if I have the time to set up the tripod, I will put the camera on the tripod and the lens in manual focus. Then I turn on live view at 10x zoom and focus manually. After focussing I go back the normal shooting mode (still in manual focus) and snap away and the sharpness is excellent down to the pixel level. Of course if the subject is moving towards or away from you, this is kind of impractical, but you can actually do this pretty fast once you get used to it and then you are pretty sure of getting a sharp photo.

I am still trying to figure out what the cause of the problem is and how to avoid it, but meanwhile I continue to use it and most of the time it works very well for me. I wish I could pinpoint the problem so I knew exactly what to do when handholding and using AF, but so far I have not been able to. Luckily it does not always happen. All in all, I really really like this lens. I would not give it up.


Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow