Reply to thread

Message

<blockquote data-quote="gustafson" data-source="post: 564098" data-attributes="member: 40735">I've been using a 200 f/4 Q.C mounted on a TC-16A as a poor man's telephoto for birds, but ended up with poorly focused shots on my last outing. I posted about this a few days ago and was advised that there seemed to be a front-focusing issue (<a href="http://nikonites.com/telephoto/36738-advice-needed-sharp-bird-shots.html#axzz4CKuipBCq" target="_blank">http://nikonites.com/telephoto/36738-advice-needed-sharp-bird-shots.html#axzz4CKuipBCq</a>). I checked the focus points and they seemed to be on the subject, so I figured that the setup could have a front focus issue (not noticeable for close-in subjects, but apparent for subjects 25 ft or beyond).Yesterday, I looked into AF Fine Tune, and got some interesting findings. My subject was a cereal box with a ruler at 45 degrees adjacent to it, about 20 feet away. At this distance, however, AF seemed to be accurate as far as I could tell. Just for grins, I dialed in an adjustment of -20, and didn't see much of a change in the photo. Then I dialed in +20, and again, nothing seemed to have changed. This surprised me a little. Wondering if there's an explanation of this, and more importantly, if there's a preferred way to diagnose a front focus / back focus issue and correct it with AF Fine Tune. Thanks!</blockquote>

[QUOTE="gustafson, post: 564098, member: 40735"] I've been using a 200 f/4 Q.C mounted on a TC-16A as a poor man's telephoto for birds, but ended up with poorly focused shots on my last outing. I posted about this a few days ago and was advised that there seemed to be a front-focusing issue ([url]http://nikonites.com/telephoto/36738-advice-needed-sharp-bird-shots.html#axzz4CKuipBCq[/url]). I checked the focus points and they seemed to be on the subject, so I figured that the setup could have a front focus issue (not noticeable for close-in subjects, but apparent for subjects 25 ft or beyond). Yesterday, I looked into AF Fine Tune, and got some interesting findings. My subject was a cereal box with a ruler at 45 degrees adjacent to it, about 20 feet away. At this distance, however, AF seemed to be accurate as far as I could tell. Just for grins, I dialed in an adjustment of -20, and didn't see much of a change in the photo. Then I dialed in +20, and again, nothing seemed to have changed. This surprised me a little. Wondering if there's an explanation of this, and more importantly, if there's a preferred way to diagnose a front focus / back focus issue and correct it with AF Fine Tune. Thanks! [/QUOTE]

Verification