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DPChallenge Forums >> Hardware and Software >> Auto focus 35mm lens out of focus???
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Nikon D70s
 05/27/2003 09:29:28 AM · #1
I recently bought a 24-120mm Nikon zoom lens, used from a Nikon dealer. The lens is in great shape, no wear and tear etc....

However, every once in a while I swear my pics are just a hair off of perfect focus. I have two other great lens that are razor sharp.

My question is, is there a way to determine if auto focus is right or slightly off. Would I have to ship to Nikon to know for sure?
Canon EOS-20D
Canon EF 17-40mm f/4.0 L USM
 05/27/2003 11:44:53 AM · #2
A good way to find out it do the famous ruler test. Take a picture of a ruler from a diagonal position. For example, take a picture of the number 6 using a wide aperture and see if it is in focus, or slightly in front or in back. It the latter is the case, you'll need to have your lens calibrated by a Nikon Service Centre.

You can also use a book or a newspaper. Focus on a specific word, take the picture with a wide aperture, then see if the word is in focus or if other surrounding words are in focus.

Good luck. Hopefully it's just camera shake. :)
Canon EOS-1000D Rebel XS
Canon EF-S 60mm f/2.8 Macro USM
 05/27/2003 12:10:44 PM · #3
One comment about the ruler test. If you do this test be sure to do it in bright daylight. The goal here is not to trick the autofocus, but instead give it the best chance possible to get it right. When all the noise was going on about the 10D focus problems I did this test. I mounted the camera on a sturdy tripod with my 50mm f/1.8 lens. There is a piece of equipment outside at my work with a bunch of bolts sticking out in a line spaced about ½’’ apart. I took a black marker and colored one black, the rest are a light green color. I selected the center focus point and moved the camera so that the bold filled the center focus sensor box in the viewfinder. With the lens wide open I manually focused at infinity and then let the camera autofocus and took a picture. I then returned the camera to infinity and repeated 9 more times. I then did the same thing starting from the minimum focusing distance. What I ended up with was 20 pictures with the black bolt in perfect focus and confidence that my camera was focusing correctly. BTW the camera was at about a 45 degree angle from the line of bolts. I would suggest doing a similar test to this instead of using a ruler. Rulers don’t always have optimal contrast for the AF sensor to lock onto.

Greg
Canon EOS-1D Mark II
Canon EF 70-200mm f/4.0 L USM
 05/27/2003 12:16:53 PM · #4
Are you close to the subject?

If you're close and you have wide open aperature or small DOF, then just the tiniest bit of movement will cause it to be out of focus (that is if you recompose the shot, that alone could cuase the subject to be OOF). Use a tripod if you are doing this, or better yet, tripod + manual focus when up close (such as macros)


Originally posted by Kneeforu:
I recently bought a 24-120mm Nikon zoom lens, used from a Nikon dealer. The lens is in great shape, no wear and tear etc....

However, every once in a while I swear my pics are just a hair off of perfect focus. I have two other great lens that are razor sharp.

My question is, is there a way to determine if auto focus is right or slightly off. Would I have to ship to Nikon to know for sure?
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