Lens calibration

emlopes

I have gone through all the titles in this forum, but found nothing related to lens calibration. I have a focus problem, and have approached it according to several suggestions in this forum, such as cleaning the contacts, etc. I have found tips for calibrating lens for a number of cameras, but not for the D5100. I bought the camera new with two lenses: AF-S NIKKOR 18-55mm 1:3.5-5.6G and the other a 55-200mm. Both worked well for a time, but then I started getting blurred images. Since I am new at this, I am at a loss. Any advice, please?

bruto

If it's really a matter of calibration, you're pretty well out of luck for remedying it yourself. Some higher model cameras such as the D7100 allow for AF fine tuning, but not yours.

The first thing I'd do for this is to switch to Live View, and, using a tripod, aim at a static object and take some test shots to see if the lenses themselves are sharp and working right. Live View autofocusing uses a different mechanism, and because it uses the image plane itself, it can't get out of adjustment. For the most critical focusing test, keep your aperture large, so that there is minimal depth of field, and thus less tolerance for error.

Now, if the lenses pass the test, keep the thing on a tripod, switch to single point single servo auto focus, making sure that the focus point is centered, and shoot the same static object. If the lenses are not now as sharp, then the lens and the camera's AF are in disagreement. If both lenses are off by a similar amount, I'd suggest having the camera checked and adjusted. I believe Nikon service can do this. I think sometimes it can get dirty as well, but I do not know what might be required to clean it.

If the AF seems all right when you do the tripod and single point test, then perhaps what you need is to check whether your camera's AF is set correctly, and whether you've been jiggling more than you thought. But since this setup started out working well, my guess is that the AF system has gone off.

If you do have an AF problem, even though you may be unable to fix it, you can get an idea of what is wrong and in what direction, if you set up a row of objects on a table, or a long tape measure on a floor, and shoot these objects at a fairly shallow angle. Set the tape measure down, and aim at a specific point on it, or aim at a particular object in the row, using the widest aperture (shallowest depth of field) you can. When you view the image, if none of it is clear, then the lens itself is not sharp. If the lens is front or back focusing, you will see that numbers to one or the other side of the one you focused on are sharper. Even if you can't fix it yourself, you'll at least know what's happening.

emlopes

Thank you, Bruto. Will do.