I do mostly interviews and use my DSLR as the secondary camera, usually handheld and using a technique of quick zooms to give the interview a more industrial look. I start off each interview zooming in and focusing on the subject, but lately I've noticed that people have been just a tad bit out of focus.
I did some testing and found that when I zoom into a subject, say, 7 feet away. Then zoom halfway out (without me or the subject moving away/closer to each other), the lens goes out of focus, and then when I zoom all the way out it's back to being in focus.
From using my other cameras, I would just adjust the macro setting to fix this. But this lens/camera does not have anything like that. Any suggestions?