Tokina 100mm Macro Focus Issue

[radicalgel]

<p>Hi,</p>

<p>I use my Tokina 100mm Macro ATX-Pro 2.8 with a Nikon D300s and I'm having this weird issue with autofocus. Basically, if I select the center AF point on my camera the lens back focuses a little, resulting in blurry images. If I however, move my focus point to the right or left ,then focus is spot on and the images are tack sharp. This is really weird. I thought the center AF point is the strongest, but that's the one thats giving me this issue. I know it's not the camera as my Nikkor 50mm 1.8G and 70 - 300 VR work fine. So is my lens faulty or am I doing something wrong?</p>

[Wouter Willemse]

<p>Does it happen always, regardless of subject distance? If not, it could be the focus limiter.</p>

[radicalgel]

<p>Thanks for the response but it's not the limiter. Tried with it on full and limit and I have the same issue. Subject distance doesn't really affect this behaviour.</p>

[eric_arnold]

<p>i have that same combo. just tried to replicate your issue and center AF point worked fine. maybe try cleaning the lens contacts? also, has this happened before and is this a new lens? and do you have other bodies you use the tokina on?</p>

<p>super sharp lens, btw.</p>

[michael_bradtke]

<p>I'm just wondering if the center AF point has always back focused at close range and using this lens is just showing you the problem. Have you tried to fine tune the focus?<br>

Oh just read your post about distance not seeming to matter.</p>

[stefan_g]

<p>Does it depend on the f-stop that you are using to take the picture? </p>

[radicalgel]

<p>Ok so I did some more tests and AF finetune on +10 is given me considerably sharper images. I am doing these tests with the aperture wide open as it reveals problems better. I am wondering if I should get it replaced as it's still under warranty?</p>

[eric_arnold]

<p>sounds like decentering. you could try to play sample roulette, but there's no guarantee the next copy won't be worse. (in all fairness to tokina, there are tolerance differences between every camera and every lens). but that's why nikon has AF fine tune, which is designed to work on prime lenses. if the problem goes away with AF fine tune, then isn't that a solution?</p>

<p>a few more questions: does the problem persist at closed apertures? if not, when does it start to go away? can you live with that? realistically, how often do you need to shoot @2.8 or AF with a macro lens? -- for anything approaching 1:1 or 1:2, one generally has to stop down (and use support). also, what shutter speed are you using? does using a faster shutter affect the image at all? and, are you testing on a tripod?</p>