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Message: <blockquote data-quote="tdodd" data-source="post: 1412264" data-attributes="member: 55450">I've just been outside to calibrate the microfocus adjustment on my 1D3, using the Tim Jackson focus test chart I linked to earlier - <a href="http://www.focustestchart.com/focus12.pdf" target="_blank">http://www.focustestchart.com/focus12.pdf</a>. Here is the result (screen print) of an AF test with no adjustments. <a href="http://picasaweb.google.com/EezyTiger/POTN?authkey=YwMQelbhTZY#5304493729170365090" target="_blank">http://picasaweb.google.com/EezyTiger/POTN?authkey=YwMQelbhTZY#5304493729170365090</a> As you will see I have a focus target that is parallel with the sensor plane and large enough that there can be no doubt that the AF sensor in use has picked the correct target. The focus point is not highlighted because I use back button focus only, so AF was not active when I released the shutter. If you look at the DOF as it alters from front to back you will see that mostly everything in front of the plane of focus is pretty sharp, but it goes downhill fast to the rear of the focus target. This body/lens is front focusing by maybe 2-3". On a small bird, if you're cropping tight, that focus error is easily enough to make the shot unuseable. If I was aiming at a bird facing towards me and focused on the eye I'd have a sharp eye and bill and the whole body of the bird would be soft. Now, because I have microfocus adjustment on the 1D3 I can tweak the focus setting to eliminate that small error. On earlier/lesser cameras that option is not available. I haven't adjusted the lens/body yet but once I have I should get images that are as sharp as the lens can muster for any given aperture. <break for lunch> Here is the equivalent image with a microfocus adjustment setting of +6. I did take down and re-setup the gear so maybe the framing is a tad different but nothing that will alter the results. The lighting has also changed but it does not matter. <a href="http://picasaweb.google.com/EezyTiger/POTN?authkey=YwMQelbhTZY#5304501576961609778" target="_blank">http://picasaweb.google.com/EezyTiger/POTN?authkey=YwMQelbhTZY#5304501576961609778</a> Note how there is a pretty even balance of acceptable sharpness both in front of and behind the focus target. I did increment the adjustment, one step at a time, and there is a clear trend from one shot to the next of improving focus accuracy. Note that the +/-50mm marks are both notably soft and about equally so. Ditto the +/-40mm marks, although they are acceptably sharp, especially if not cropping. I am happy that +6 is a good adjustment for this lens. I think + 7 is equally satisfactory. The point is, if a 1 series body and L lens can focus this inaccurately (before adjustment), who is to say that a lesser body and lens may not also suffer from miscalibration woes? Finally, here's the same lens on my 50D. With this combination I only need the microfocus adjustment set to +1. <a href="http://picasaweb.google.com/EezyTiger/POTN?authkey=YwMQelbhTZY#5304505235265966274" target="_blank">http://picasaweb.google.com/EezyTiger/POTN?authkey=YwMQelbhTZY#5304505235265966274</a></blockquote>

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