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Are their "good" and "bad" copies of lenses?

Started Jan 6, 2015 | Polls thread
Andy Blanchard Senior Member • Posts: 1,349
On lens tolerances...

Apparently, Canon (and presumably other manufacturers) allow for a little imperfection here and adjust this via a setting on both camera and lenses. In Canon's case think this is a scale that runs from +5 to -5 with L lenses and 1-series bodies requiring a setting of no more than +/-2, but it's been a while since I discussed this with CPS and I might have the numbers wrong. The sum of the two values then provides an adjustment bias to the focussing mechanism that should correct the error(s) and bring things back into spec.

Where this comes unstuck is when you have a lens and body that are individually within acceptable tolerance, but in combination are beyond the ability of the system to correct, for instance a body with a setting of +2 and a non-L lens with a setting of +4 (which is the issue I had - CPS replaced the lens which fixed the problem). This is why you'll sometimes see issues with a lens having focussing issues on one body but not another, and why people often send both lens(es) and body in when they are having lens recalibrations done.

Andy

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