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<blockquote data-quote="BackdoorArts" data-source="post: 516812" data-attributes="member: 9240"><p>Not sure what you mean by &quot;auto-tune&quot; - perhaps the focus tuning calibration adjustment?&nbsp; On zoom lenses I ascribe to the prevailing wisdom that, all things being equal, you calibrate to the long end of the zoom, wide open.&nbsp; Sometimes, however, all things are not equal and AF adjustment can swing wildly at extremes.&nbsp; For example, on something like a 70-300mm you could be somewhere like -3 to -7 from 70mm to 250mm, and then all of a sudden at +4 at 300mm.&nbsp; That's where you need to make a decision based purely on usage.&nbsp; This level of deviation isn't typical, but a deviation at the extreme isn't unusual, so knowing how your lens acts can help you make your decision.&nbsp; In a case like this, I'd set the calibration for the bulk of the lens sweep (probably around -3 or -4) and know that when I'm at 300mm I want to close down the aperture and boost my DoF.</p></blockquote><p></p>

[QUOTE="BackdoorArts, post: 516812, member: 9240"] Not sure what you mean by "auto-tune" - perhaps the focus tuning calibration adjustment? On zoom lenses I ascribe to the prevailing wisdom that, all things being equal, you calibrate to the long end of the zoom, wide open. Sometimes, however, all things are not equal and AF adjustment can swing wildly at extremes. For example, on something like a 70-300mm you could be somewhere like -3 to -7 from 70mm to 250mm, and then all of a sudden at +4 at 300mm. That's where you need to make a decision based purely on usage. This level of deviation isn't typical, but a deviation at the extreme isn't unusual, so knowing how your lens acts can help you make your decision. In a case like this, I'd set the calibration for the bulk of the lens sweep (probably around -3 or -4) and know that when I'm at 300mm I want to close down the aperture and boost my DoF. [/QUOTE]

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