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I received a call from two clients this past week complaining about getting good focus on their images. After viewing some images it became apparent to me the camera was not focusing accurately on the focus points, on one particular camera it seemed to focus a little before the desired plane. So I just spent the last two days calibrating lenses for clients. It made me realize I never did the lens calibration when I got my 1D Mark4. I had done the test for my 1D Mark 3 and my 1Ds Mark 3. I found the test made a difference in the sharpness of my pictures. So after working on my client’s cameras, I decided to do mine!
To do my current tests and those for my clients I used the Spyder Lenscal by Datacolor. This is a well made plastic target that folds up small for storage and opens up to give you both an angled target for judging whether you have a front or back focus problem, and a vertical target that is made up of black and white squares with a lot of contrast for the AF system to easily focus.
Not every camera lens combination will give you perfect focus every time, but if you calibrate your lenses to your camera bodies you get a much better chance for super sharp images! I set up the Lenscal on a tripod and made sure it was level with the built in level.
I then set my camera on another tripod with the lens I wanted to test, in this case my 100-400mmL lens. I stood back far enough so that target only filled the center circle area of my viewfinder. Canon recommend you are 50x the focal length of the lens in distance. I didn’t really measure, I wanted to make sure the camera could see enough of the target to focus, and be as far as I could and still achieve this. Then I went to the Micro Adjustment settings in my Custom Functions in the Autofocus/Drive Group. And shot with a -5, 0 and +5 setting to get an idea which way the lens was focusing. I then found it was sharper with the minus setting so I shot more tests at -20, -15, -10 and -5. For a good description on how to run the test go to: http://bit.ly/kUJ4oE to see how Chuck Westfall from Canon recommends the test is done.
Use “Same amount for all lenses” when conducting the test
Once you determine how much correction is needed to get your lens to focus perfectly then you set that for that particular camera body/lens combination by selecting “Adjust by lens”.
Setting the correction for this particular lens and body combination.
Now when I use this correction I get great focus out of my lens!
Set to -15
If you may be questioning the sharpness of a lens or your ability to get a lens to focus exactly where you want it to focus then I recommend you do this test and calibrate your lenses to each camera body you own. It will make a difference!