Re: I am an idiot and need to have my eyes checked
Jonas is correct. AF adjust has NOTHING to do with manual focus. Nada. Zippo.
Accurate MF relies on the distance from the rear mount of the lens to the sensor being EXACTLY the same (did I say EXACTLY?) as the distance from the rear mount to the focus screen. If they are off even a minisucle amount what looks in focus to you wo\'t be - the plane of focus will be just in front of or just \'behind\' the plane of the sensor.
The 5D (and one can assume the 5DII given it shares the same body, mirror box, etc) is infamous for many copies needing to have their focus screen re-calibrated IF the factory installed focus screen is replaced with ANY (as in ANY) other focus screen - even ones sold by Canon for the 5D.
5D/IIs are \'calibrated\' (I use the term loosely when referring to Canon) at the factor so that when the AF locks on to something what you see in the VF is \"acceptably\" sharp. As an AF camera, they are not calibrated for Nth degree accurate manual focus. As well, ANY change in focus screen vs. the actual copy that was factory installed will screw-up any attempt at accurate MF.
Shims from (obtained) Canon can be changed (thicker/thinner) or you can use thin strips of scotch tape or metallic duct tape on the edges of the new screen in lieu of adding shims. You can also send the camera and new screen (Canon only of course) to canon for calibration as well - but you\'d likely do a better job yourself.
1 Series bodies don\'t have the same issue. You can change focus screens 5x a day in any one them with no issues.
Dec 16, 2008 at 08:42 AM
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