One of my more embarrassing on-set moments happened when, years ago, I had been hired as a camera operator on a multi-camera shoot. Sometimes talking your way into a position can you get you into trouble, and I wasn't really qualified to be operating a full size camera, which I discovered when the backfocus was off. I didn't know how to adjust it, given at the time I'd only shot on Sony DV camcorders, and had to call on another camera operator to do my job for me. The horror! So here is a tutorial for setting back focus from The Complete Guide to ProHD Volume I, which applies to many videocameras (not just the JVC on which it's demonstrated). But first, what is back focus?
Back focus refers to focal flange length, which is the distance between the rear lens element and the camera's sensor. On cameras with interchangeable lenses, sometimes changing a lens will also change the focal flange length, and the discrepancy can cause an image that's sharp when zoomed in to be soft when zoomed out. If that's the case, you need to adjust the back focus. Here's how to do it on a JVC Pro camera, but the process is similar on many cameras (here's how to do it on a RED EPIC/SCARLET):
As interchangeable lens cameras become more and more prevalent, I thought this might be handy.
[via DV Info]