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<blockquote data-quote="Horoscope Fish" data-source="post: 356464" data-attributes="member: 13090">What I did with my zooms was test them at three different focal lengths and always wide open. What you have to be careful about is not mistaking softness for front/back focus. My Nikon 18-140mm needed a little adjustment but was very soft at 18mm. My big Sigma 50-150mm needed the most adjustment but was sharp at all focal lengths. The 18-140mm was tested at 18mm, 85mm and 140mm while the Sigma was tested at 50mm, 100mm and 150mm. The other thing is depth of field... Since a lot of zooms are, for instance, f/5.6 wide open at maximum focal length, depth of field can make it hard to determine if there's significant front/back focus going on. You just have to try and see what you find. You can always revert the settings back to &quot;0&quot; or simply shut off the AF Fine Tune option all together so there's no danger in playing with the setting.There are other methods for confirming and correcting autofocus (like the Dot Tune Method) but I found the procedure listed on the Nikon website the easiest one to do quickly. Still, you might want to look around and see what some of the other options are.....</blockquote>

[QUOTE="Horoscope Fish, post: 356464, member: 13090"] What I did with my zooms was test them at three different focal lengths and always wide open. What you have to be careful about is not mistaking softness for front/back focus. My Nikon 18-140mm needed a little adjustment but was very soft at 18mm. My big Sigma 50-150mm needed the most adjustment but was sharp at all focal lengths. The 18-140mm was tested at 18mm, 85mm and 140mm while the Sigma was tested at 50mm, 100mm and 150mm. The other thing is depth of field... Since a lot of zooms are, for instance, f/5.6 wide open at maximum focal length, depth of field can make it hard to determine if there's significant front/back focus going on. You just have to try and see what you find. You can always revert the settings back to "0" or simply shut off the AF Fine Tune option all together so there's no danger in playing with the setting. There are other methods for confirming and correcting autofocus (like the Dot Tune Method) but I found the procedure listed on the Nikon website the easiest one to do quickly. Still, you might want to look around and see what some of the other options are. [COLOR=#ffffff]....[/COLOR] [/QUOTE]

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