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Old January 27th, 2008, 03:14 PM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Join Date: Jun 2006
Location: Netherlands
Posts: 4,054

Originally Posted by Andy Bennetts View Post
Bart - thanks for an ideal quick method to apply the microadjustment. Works a treat (well almost - see later) and I've set up my 70-200 f2.8 at +13 and my 24-70 f2.8 at +20.
This last lens still shows a very slight focus shift even at +20, and the lens is brand new. It doesn't seem to affect the pictures, but to be fair, I haven't had much experience with the lens yet. I'm surprised Canon's quality control has resulted it a lens that it at least in pure technical terms, a bit "off".
Any comments from anyone - should the lens go back to Canon to be set up properly?
Hi Andy,

I also have one lens with an 'extreme' AF-microadjustment setting (+19 if I remember correctly). What it means is that for the specific body/lens combination the tolerances are perhaps a bit skewed to different directions, which results in a cumulative adjustment that's that far off to one direction.

The trouble with many zoom lenses however is that the short and the long end require different amounts of correction. It therefore depends on how you use that lens, whether it makes sense to send it in for re-calibration. When you usually shoot wide open, things are much more critical than when you often use average apertures. When you shoot mainly at the longest focal length, things are again more critical due to less DOF.

In general, if most lenses are close to zero (say +/- 10) and one lens is much more out of range (say + or - 20), and if it is an issue because it's not enough, and due to your type of shooting you need to get it better, then try sending it in and see if it helps. When all lenses are skewed to one extreme side, then the body might need some recalibration as well and it is best to send in both/all, but only if you can't fix it within the +/- 20 adjustment range. As long as it can be adjusted with the AF-microadjustment, there's no real issue.

The only question I personally have is; does zoomlens re-calibration allow to get rid of the differences between the short and long end, as that's the most anoying thing left? It's maybe too soon, but it would be helpful if someone (with AF-microadjustment settings before and after) could answer that from experience.

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