Tips and Techniques
Adjusting focus on EOS 1D-MKIII.
Not all lenses and camera combinations are created equal. Some lenses work perfectly and other lenses require a camera adjustment to ensure proper focusing. Fortunately this is an easy adjustment on the EOS 1D-MK III. This is done individually for each lens through the camera custom function C.Fn III 7. The camera keeps track of every lens and converter combination. Follow screen directions to adjust focus forward or backward as needed according to your finding using the jig below.
FOCUS CHART on plywood backing
Making the jig is simple. Download and print out focus_chart and paste it to a piece of plywood or stiff cardboard so that it can stand up straight or just prop it up somehow. Keeping it flat and vertical will help greatly in analysis of the focus lines of the chart.
Set up the board at a 45 degree angle to your camera at a distance comfortable for you, or the distance you most often shoot at, and autofocus on the centerline of the chart using the center focusing square. Shoot wide open to minimize depth of field.
You can see a bit of backfocusing here.
Analyze your photo and determine which line is most in focus. Shift focus in small increments using C.Fn III 7 backward or forward as necessary, re-shoot, re-analyze and re-peat till focus is perfect. Repeat for all lenses and converter combinations and your done!
Some of my lenses required no adjustment yet my 24-70 L required +15. Your mileage will most certainly differ.