Why is it important to use the Distance Tool when using LensAlign?

Almost all of the DSLRs that have an AF adjustment, only have the ability to set one adjustment value. Since the AF system is not a linear system, it is not possible for the adjustment to be perfect at all shooting distances. So it is important to test and adjust the camera/lens combination at a distance that will work well at most all shooting distances.

If the test/align distance is too short, the AF system could be compromised at longer shooting distances. But when the test/align distance is equal or greater than the MRD (minimum recommended distance), as determined by the LensAlign Distance Tool, it is likely that the AF accuracy will be improved at all shooting distances, both closer and further than the test/align distance.

The MRD is generally accepted to be 25 times the focal length of the lens under test (you should ignore any sensor crop multiplier). This is the distance that the LensAlign Distance Tool calculates. It comes out to 8.2 feet for each 100mm of focal length (allows easy in-head calculations for Americans:>). If conditions allow, then 1.5x the MRD is ideal.

Since the AF adjustment can only be perfectly accurate at one distance, if you shoot at a specific distance or small range of distances (like head and shoulder portraits), you should always test/adjust at that specific distance even if it is less than the MRD.

We suggest to measure from the center column of one tripod to the other. The reason for this, is so you retest a specific camera/lens combination, you can repeat the same distance and not have to figure out how you measured the distance.

Bottom line...Test and set the AF adjustment at the distance that you shoot, or for a generic setting at 1x to 1.5 times the MRTD, as determined by the LensAlign Distance Tool.