How to perform Lens AF Micro Adjustment on a Canon EOS DSLR
1) Mount camera on solid tripod.
2) Place reference target on wall or stand so that it is centered, level and parallel with the camera's sensor plane. The reference target can be anything that provides good contrast and detail to ensure the AF will lock and that you will be able to determine best focus from the photo. I recommend taking a color page from a magazine that contains a contrasty photo or graphic and small text. Make sure the reference target has adequate and consistent lighting.
3) Mount lens on body and move tripod so that it is 50 times the focal length (50mm equals 2.5 meters/8.2 feet). For the longer lenses this may prove difficult if you are working indoors, so just make sure you use the principle of further away for longer focal lengths and make sure you at least have 15 feet to work with in.
4) Look through viewfinder and make sure you are centered and all set up.
5) Set camera to aperture priority mode or "A" on the dial. By turning the dial near the shutter release open the lens all the way up (smallest possible number or largest actual aperture opening). Enable mirror lock up with 2-second timer delay. Make sure the lens AF is on and that the IS (Image Stabilization) is turned OFF!
6) Go into the menu and select AF MicroAdjustment for the specific lens that you have mounted on the camera, do not adjust the overall AF setting. Start off with -5, 0 and +5 for each lens. Take three shoots at each AF setting.
7) Get paper and pencil to record the sequence of lens and AF settings.
8) Now you are ready to shoot, but make sure that you twist the lens focus all the way to infinity before each shoot! Also remember to take three shoots at each AF setting and that you need to manually go back into the menu to change the AF setting.
9) Load the photos into viewer (Apple's Aperture for example) and zoom into 100% at the center of the photo and figure out which grouping of 3 photos is the sharpest. Keep in mind that there will be some difference in focus sharpness between each of the 3 photos in the grouping, so just look for the average.
As an alternative to downloading the files you can simply review the photos on the camera's LCD by zooming to the maximum setting.
10) Once you determine which group of photos is the sharpest, then you need to start over and go through the process as many times as needed to figure out the precise setting. For instance, if +5 looks to be the best then you will need to shoot from roughly +3 to +7 to know the exact setting.
Sounds like a pain but once you get a hang of the process it goes fairly quickly.
Best of luck,
© Chad Kirkpatrick : Witness to Beauty ® Photography