Help 70-200 back focus

siejones

siejones

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I just brought a second hand canon 70-200 F4L and I think it's got back focus problems

I was a bit dubious about it's sharpness so I tested it against my sigma 70-300 APO DG both at 200mm. The sigma seemed to be generally sharper in the corners but not so in the centre where the canon seemed to be better.

Confused by this as the Canon should beat the Sigma hands down corner to corner I tried a few back/front focus tests. Everyone I try it seems the canon is back focusing.

Simga shot

sigtest.jpg


Canon shot

cantest.jpg
 
Send it to the service center for a check, if you think something is wrong then you will get it fixed if there is.
 
that's a shame if it is as it's the sharpest 70-200 out there. Like mho01 says, send it to Canon to check out.
 
Can anyone recommend a good one closest to west midlands. I have heard some of them aint too good?

Can't believe I may end up spending in total with second hand purchase price more than I would have payed brand new. F@&*ing lesson learnt!
 
Thanks mho01

If anyone can tell me I am wrong and I am doing something stupid I would be greatful.
 
Exif says 1/4 second at F4. The 70-200 when I used one performed quite well in average light but was stunningly good once it had good light. Light level must have been quite low for those settings.

Maybe try it again in very good light to see if the result is similar and try different distances to the target. I assume you have turned off all but the centre AF point on the camera?

Also what do you see when you look through the camera - if you manual focus it is it still out on the picture?
 
Sorry I put the F4 version of the sigma up sorry. I can re-assure you that the F5 version is very similar and still shows the same results.

You are right I am using indoor lighting for this but also a tripod remote shutter and mirror lockup. I would expect the Canon to perform much better that the sigma on low light anyway. The sigma pulls off the same results every time.

Through the viewfinder it looks good on all lenses tried.

Heres another example..a grubby sugar jar...focus was on the centre.


Sigma

sigtest2.jpg


Canon

cantest2.jpg


Notice how the further around the jar you go the more in focus the canon shot becomes compared to the sigma shot?
 
Definately looks a bit off.. back to canon/repairers with it :(
 
I have today dropped this off at

http://www.lehmannsdirect.co.uk/ In Stroke on Trent.

They have quoted me £63 for a service that they said will be include alignment to fix the back focus.

I keep reading of horror stories on forums of canon service centres and it worries me now.

Anyone used this place before?
 
siejones said:
I have today dropped this off at

http://www.lehmannsdirect.co.uk/ In Stroke on Trent.

They have quoted me £63 for a service that they said will be include alignment to fix the back focus.

I keep reading of horror stories on forums of canon service centres and it worries me now.

Anyone used this place before?
Click to expand...

Lehmann's, Fixation and Canon Service Center are 3 of the best in the Country.

Why dont you just wait till you get it back and then comment on how it is.
 
Atleast this lens is going to get checked out by professionals, it will be serviced, recalibrated, and to be honest should be better than new in terms of sharpness - dont worry, just wait till you get it back :)

Good Luck:thumbs:
 
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