Zoom lens AF tune on Nikon D300 caveat !!!

<p>I do believe this question has been made already but I don't see any procedures given to perform this task accordingly. Is there anyone that has done this before and help me out ? I need to know for example : <br>

1 - Distance from the camera to the subject <br>

2 - What type of subject to use ( some photographers have used things not a chart suggested by most professional photographers ) <br>

3 - What aperture, speed and ISO<br>

4 - What focus distance to setup on the lens ( here is the tricky part; according to Thom Hogan's book about the D300 - page 388 - <strong><em>"you are only making an adjustment for the focus distance you tested </em></strong><em>you can not calibrate a lens twice so if you calibrate a zoom lens at its closest focus distance and then use your lens mostly at the far focus distance, don't expect your calibration to be accurate " !! </em><br>

This lead me to the conclusion that for prime lenses, AF TUNE may work perfectly, but for zoom lenses, there is a caveat.<br>

This also lead me to the question that how to perform a AF TUNE for a zoom lens that works for the entire focus distances available ? Well, I don't think it is possible according to Thom, but again, if I AF TUNE for example my Nikon 70-300 mm VR at 150 mm, would that means that if I choose any other focus distance while shooting, my pictures will be out of focus or horrible unsharp ? <br>

So how a lens that is coming well tuned from factory, is sharp at all focus distances available and a lens that is out of focus at any chosen focus distance can not be AF TUNE entirely in its zoom range and if you do so, according to Thom, <strong><em>"don't expect your calibration to be accurate"</em></strong> ? <br>

Can a lens be unsharp, unadjusted, out of focus at just one focus distance but sharp at the others ? And if so, and you fix it, will unsharp the rest and sharp the one fixed only ? How does this work ? Is the AF TUNE option in the D300 <strong>"limited"</strong> in its capability to correct only one focus distance or is this something that Nikon technicians could correct for the entire focus distances in any particular zoom lens ? Do they have that capability while the AF TUNE in the D300 does not ? <br>

Sorry if I am confused and if I am, that why I am posting this question to get help from those that already tested this option in the D300 and know exactly what to do. Thank you in advance. <br>

Best regards !!</p>

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<p>If Nikon had a true f2.8 or f4 lens in the VR 70-300mm lens selection linup, the fine-tuning feature would be really neat. But the lens you have (the AF-S 70-300mm VR model) is not a single f-stop design, so as you zoom the lens, the focus point shifts. That is the physics side of lens design. Each time you change the zoom length, the focus needs to be 'touched up' or adjusted. This is something the fine tuning function has a slight problem overcoming (my estimate.) Are you having images turning out out-of-focus with your D300 and the VR 70-300mm lens?</p>

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<p>I've never noticed a focus problem with any of my AF lenses on my D300, or any other Nikon DSLR. What am I doing wrong?</p>

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<p>not a single f-stop design, so as you zoom the lens, the focus point shifts</p>

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<p>Jerry,<br />Could you explain the relation between the "F-Stop" (aperture) and Focus point ? (apart from cahnging DOF that is ). I seem to have missed that for some reason..<br />As I understand it, theactual Focus point does not change with F-stop, other than that the DOF changes when you change aperture, but the focus point remains where it is...</p>

<p>F/stop or aperture values do NOT affect the focus plane...Not sure how you arrived at that?</p>

<p>(F.L) (Focal Length) DOES affect the plane of focus unless you are fortunate enough to have "Par-Focal" lenses, which I do not think exist in multiple FL lenses (Zooms) made for cameras.</p>

<p>No more to add.</p>

<p>Hi Maurice'<br>

Here is a copy of my post of a couple of years ago explaining how I did it.<br>

Here is a copy of my previous post about my experiences with AF fine tuning.<br /> I AF tuned my 80-400VR and my 24-120VR and was very pleased with the results. I focused at a target of cars a city block away. The adjustments were in 2 units per picture. I started at +18 and went to -18. I used live view to focus. This was done at 80mm, 200mm and 400mm on the 80-400VR and 24mm, 70mm,and 120mm on the 24-120VR. I picked cars so that I had sharp lines in all directions and sharp contrasts including various colors.<br /> <br /> If you use NX2, the AF tuning number is displayed. I then looked at 300% at each shot and selected the best ones and tabulated the AF numbers for those. I averaged the numbers for the best looking shots. Some shots were too close to tell a difference so I took the next worst shots and wrote those down.For example +10 slight blur +2 slight blur. Split the difference or halfway between those and you get +6. Do this for min focal lenth then again for medium and last for max focal length. When you get all three average them again. I found no difference in the numbers between the various focal lengths on each particular lens.<br /> The 24-120 wound up at +8 and the 80-400 at -4 AF tune numbers. There is a good improvement doing this. All shots on a tripod with MLU and shutter delay to stop vibrations.<br /> To get used to AF tuning play with the AF tune function in the menu and see what happens. You can't screw anything up and it is a feature you should know how to use. Nikon added this feature because they knew there is a problem.</p>