
Originally Posted by
HDNitehawk
The components inside the camera are very sensitive. If there off a bit they will send the wrong information to the lens. You could have bumped it or shaken it, or just general wear and tear changed things. If you compare the lens all the way through all of the settings then you can decide what is appropriate. There is nothing wrong with switching settings in the field if a subject is closer or further. Or you could do an average of the two ends. I prefer to set to the long end since the DOF is narrower there.
It my understanding that there is variance in the mfg process, notice the latest release of the 24-70 II. So it is best to send camera and body in that way Canon can make sure it matches manufactures specs in performance.