My new 70-200...focusing probs...

[Neilyb]

Okay, after my intitial excitement I have been out at the weekend and noticed that this lens seems to have a problem focusing at times. Now, in England there is not a cloud inthe sky and light isn't a problem but I have noticed that the lens seems to hunt (maybe the 350D isn't accurate enough?). Anyway I have noticed that quite a few of my pictures show the subject out of focus (slightly) and something in the back perfectly sharp...so I tested the lens:

http://www.neilyb.de/200mmbackfocus.jpg

This is at 200mm, tripod mounted, 40 degrees....sometimes it works fine, sometimes not. The problem seems worse at 70-150mm where I get 3 or 4 out of ten sharply focussed. (I tried with the battery test and despite not moving anything the lens hunted each time I pressed the shutter)...?

Should I be doing soemthing or do I have a duff lens? Like I say when it is sharp, it is very, very sharp. Occasionally I notice blurred images from movement but most of my pictures were over 1/400sec...

[GyRob]

A1 SERVO can miss focus one shot should nail it though.
Rob.

[Neilyb]

I switched to One Shot for this reason, same problem only I was able to overide with MF if I felt necessary. I have till Wednesday (7-day cool off period after purchase), although this is not for faulty equipt, to ring them up and get it changed. I don't want to have to send it to Canon as I have a holiday coming up in two weeks. I thought buying a pretty professional product I would have nailed my lack of zoom! :(

[Choderboy]

I'd be trying to test the lens on a different body. Can you do this at place of purchase? Maybe another 350D as well as a different model - 20D/30D whatever.

I'm assuming as you resorted to focus chart test after suspecting a problem , you have probably taken enough real world shots to be confident the lens is back focusing, not just having problems focusing on a particular subject.

Might as well get things happening before the cool off period ends..

[nation]

Are you shooting the battery test against a zero contrast background? Given the minimum focusing distance of the 70-200 the focusing area of your chosen AF point will be greater than the area of the battery visible through the lens. The AF may be catching a high contrast area in the background rather than battery.

Presumably you've tried all the AF testing tricks in the testing website. If yes then I agree with you the test results show slight back focus.

As for the blurred images. If it's not consistantly blurred and occurs with a tripod then the only thing I can think of is getting used to the lens length.

[Albert Harrison, Jr.]

I've read in my EOS 20D owner's manual that trying to focus through bars or repetative patterns on a surface, can fool the camera's autofocus. Try shooting something else besides what you posted here. Maybe a floral print or something.

[Neilyb]

When I have chance to edit and post some pics I will. But I tested the 17-85, tripod mounted and the 70-200 (which was at 81mm) focusing on the same, same app..et..and the 17-85 hit the spot, the 70-200 didn't.

The bettery test was done on a tbale top, level with the lens. It didn't focus on the background (unless it front focusses by about 6ft :) ) and the back battery was in focus or the back of the middle battery was..and sometimes it focussed righ .Very inconsistent considering the solid tripod mounting.

I am confident the camera is good as it was off a few months back for the very same problem. But my other lenses are fine.

I like this lens when it works but there are a few shots I missed.

This is a little cropped.
http://www.neilyb.de/femalFinch.jpg

[Neilyb]

Warehouse express are swapping the lens tomorrow via curier... :)

[JRJay]

How far is your lens from the test subject. The minimum focus distance for the 70-200 f/4 is 1.2m / 3.9ft. Also, did you have the switch on 1.2m or 3m?

[::John::]

How far is your lens from the test subject. The minimum focus distance for the 70-200 f/4 is 1.2m / 3.9ft. Also, did you have the switch on 1.2m or 3m?

Yeah, I know it looks obvious - but that little switch has caught me out on more than one occassion. A lot of my shots looked like I had a focus lock - and they looked terrible when viewed later.

[Neilyb]

The focus was on 1.2m for the test, I am well aware of tht limitation. the rest of the time I was on 3m - infinity (the outdoor shots) :)

[Juan Zas]

Neil,

I had a back focusing problem with my first 70-200 f/4, but it did work not so bad at 200 mm f/4 couriously, the rest was really back focusing. I hope after exchange the lens your problem will be solved as mine.

[Neilyb]

Neil,

I had a back focusing problem with my first 70-200 f/4, but it did work not so bad at 200 mm f/4 couriously, the rest was really back focusing. I hope after exchange the lens your problem will be solved as mine.

Seems to be most incosistent at 70-150mm...always searching. But a great lens otherwise I am really impressed with the sharpness.

[danster]

As an owner of a dud lense, I feel for you Neil. Hope your new lens is sharp the it should be.

[Neilyb]

Cheers, wish it was tomorrow now ! :)

[Juan Zas]

Seems to be most incosistent at 70-150mm...always searching. But a great lens otherwise I am really impressed with the sharpness.

Pretty the same thing. After Canon Spain exchanged it for a new one, no problem, fantastic and tack sharp. the foxus did work perfect. I am very happy with the results, and it´s a light tele !!

[Neilyb]

WarehouseExp. swapped the lens by next day courier...can't wait to test it out....wish I wasn't at work.....but if I wasn't I couldn't afford the lens.... :|