D7000 & 70-200 VRII Focusing Issues

[elliot1]

<h2>Yes, I believe reading that the actual area used for AF is below the focus point in the viewfinder. I am not sure if it is true and if so, why.</h2>

[steven_f1]

<blockquote>

<p>@Elliott - You mentioned that it focuses a bit "lower" on the D7000. Do you mean that the focus point in literally lower in the frame than where the actual focus point is? If so, why would that be?</p>

</blockquote>

<p>The focus sensors are not located in the viewfinder. they are located under the mirror just in front of the sensor in your camera. The marks in the viewfinder are only a guide as to where they are. Due to alainment tolerances of variouse parts of the cameras the marks in the viewfinder may not line up axactly with the location of the AF sensors in the picture. Furthermore the area of the image that the AF sensor sees may not be the same size of as the mark in the viewfinder. I don't own a Nikon but on my camera the AF sensor actually sees an area slightly larger than the AF mark I see in the viewfinder. </p>

 

<blockquote>

<p>All tests used AF-S - Center focus point. remote release in two steps (mirror lock up, then shot).<br />Results - Negative - Definitely worse<br />Zero - Seemed mostly okay<br />Positive +3 - +5 : toss up between this and zero - It varied -</p>

</blockquote>

<p>Here is a link to a photo.net article on <a href="../learn/focustest/">focus testings</a>. You don't need to buy anything to do it. All you need is a tripod or, your camera and a printer to print out the focus chart. If you don't have a printer you can simply draw a line on a sheet of paper and tap a ruler next to it. You should not use continuous focusing for a subject that doesn't move. Us the setting on your cameras that is for stationary subject (on my camera it is call "single shot". When you use continuous flocus with stationary subjects the camersa may confuse confuse camera shake with subject motion and as a result may mise focus. If you don't use a tripod and the wrong focus mode you could get inconsistant results in your focus test. If you use a tripod and get inconsisant results there is a problem and you will need to send you lens and or camera in for repair.</p>

 

<blockquote>

<p>I believe that the focus should be sharp 1/3 in front of the label and 2/3 behind, correct?</p>

</blockquote>

<p>No, The amount of in focus area in front and behind depends on the distance between the camera and subject. In some cases depth of field will be 1/2 in front and 1/2 behind. Use a <a href="depth of field calculator">depth of field calculator</a> to determine how much in area in front will be in focus. </p>

<p>Most of the time a new lens will focus correctly out of the box and never need adjustment. However every once in a while a new lens will be bad out of the or and older lens will start having problems and need adjustment. IIn 20 years I had to send two out of warranty lens back for repair because sand got in the focusing mechanism. All new lenses that I purchases were good out of the box.</p>

[dan_south]

<p>I don't think you need to adjust the lens. The f/5.6 shot looks to be well-focused. You were tilting the lens downward slightly, so it makes sense that the base focuses a little bit in front of the bottle. The label looks spot on in that shot.<br>

<br />My guess is that this is a technique problem. I think you need to practice using your AF a bit more. Are you determining which AF point to use, or are you letting the camera do it for you? Are you sure that the point has an edge with enough contrast to lock onto for EVERY shot? Are you sure that you didn't MOVE THE CAMERA BACK A LITTLE BIT after you locked focus on with the f/2.8 shot?</p>

<p>Can you mount the camera on a tripod and reshoot your test? Can you switch to Manual Focus mode and focus using Live View for comparison at f/2.8?</p>

<p>Autofocus ins't foolproof. Getting the best results out of AF requires technique and practice and discipline. If you make a lens adjustment that you didn't really need in the first place, you'll only end up with more out-of-focus images, only this time they'll ALL be out of focus, not just some of them.</p>

[peteris_snikers]

<p>If focusing differs in continuous mode, may be its worth to check camera sentings - Custom setting menu > Autofocus > AF-C priority selection > is camera set on release or focus priority?<br>

Peteris</p>

[chris_weller]

<p>@Steven - Excellent points especially about the DOF calcs. So much to know, so much to learn.</p>

<p>@Dan - Good Analysis. I think you may have a point.</p>

<p>@Peter - I've had my issues with the AF-C. I've tried it in focus and release from 1-5 in length. I currently have it on 1. Four and Five gave me poor results, but I'm totally open to the idea that I just don't understand how to use each mode effectively. I thought having these extra options would be better (vs my D90), but I'm finding that without mastering them, it's making things worse in some cases. I read, experiment, read and try a bunch of different settings, but there are so many combinations, permutations of settings and subject matter, light and a myriad of other things, it's tough to pin down what really works. That's why I try and rely on other people opinions as a starting point.</p>

[paul_hughes3]

<p>I just found out that with my D7000 + 70-200 VRII at 200mm the focus accuracy varies by about 4-5 inches depending on whether I choose central focus points or the outer focus points. Which is bad, because it means I can only fine tune for either central or outer focus points. Setting the tuning to -20 mostly fixed it when using the outer points, but now the central points focus slightly in front of the subject. This is at 2.8. At f8 it's not that noticeable. I also tested with my 24-70 2.8 and saw the same phenomenon to a lesser degree. Setting the tuning to -20 with my 24-70 2.8 fixes the issue across all points, as close as I can tell. Very disconcerting :/</p>