Originally posted by BethC Ok, so after doing the ruler test, I dialed in +9 and it seemed to front focus, then dialed it back to +7 and it seems to be focusing right now at least on the ruler. I was focusing on the line above the 16.
The way I usually do is by laying the ruler flat on the table, taking my tripod with the camera and positioning it next to the table. You should be shooting at the ruler at a roughly 45 degree angle. You need to have it well lit in order to get accurate focus. As nomadkng pointed out a ruler with darker markers may be more helpful as it aids in auto focus. Tripod is crucial in order to check the consistency of the adjusted lens.
Originally posted by BethC Does that seem right now? and if it is right with that adjustment, is it stlll a good idea to send the lens back? would you trust this lens for some thing important like a wedding if it's had be adjusted this much?
Now it is a matter of repetition. Aim the center point at the mark where you want the focus and then switch to manual focus. Rotate to say infinity, switch to AF. AF and shoot. Do this like 5 times. Does it consistently lock focus on the right mark? If so, then it has been properly adjusted. Keep in mind you have a zoom lens. You need to perform this through the zoom range (say 50,75,100,125,135). I have never had the problem of having backfocus at one focal length but front focus at another, but i guess in theory at may be possible. In that case you would prob have to send it in. Otherwise, if AF is consistent then the adjustment is complete and you have nothing to worry about