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Message: <blockquote data-quote="tdodd" data-source="post: 1636575" data-attributes="member: 55450">The "proper" targets can be simulated by using something like a DVD case, or a box, as your focus target, square on to the camera, and and angled ruler to judge whereabouts the DOF is centred. There is no need to pay for any expensive gear. I've attached an example of a setup I used with my 100-400 before I got the 7D.For my calibration efforts yesterday I used an A4 sheet with good quality print, blu-tacked to the kitchen wall, and then shot down the hallway to judge focus accuracy. By using Live View at 10X, and also Live AF as a double check, I was able to determine whether the focus was bang on or a little off. I could tell whether I was back or front focused depending on which way I had to turn the focus ring (a microscopic fraction) in order to increase sharpness. My conclusion yesterday was that +5 seemed good, although I could pretty much have left it at 0 as well. However, that was at a distance of ~7m. Today, out in the field, I noticed a touch of back focus when shooting the crow standing on the grass, so I reckon I don't need the +5 for subjects at a greater distance.I have read, only once admitedly, that Canon does purposely engineer in a little fornt focus, but I really don't know whether that's true. However, I can see some sense in it for action when a subject is likely to be approaching the camera, since maybe it helps out a little with servo tracking by keeping the plane of sharpness just ahead of the subject, ready for it to move into while the mirror and shutter are doing their thing. Who know? Probably all smoke and mirrors.Anyway, the tracking seems good. I just need to double check that it is tracking in the right place.</blockquote>

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