Did some testing with the GH2 and Olympus 12-50mm zoom in E-Zoom mode. The lens doesn't appear change focus at all while zooming, but quickly re-hunts depending on focus mode. I found the best results were using AFC, and giving the zoom a little help with a half-depress when zooming was completed. Manual zoom mode (not available using the nauticam port with the zoom/macro gear) seemed to focus a little bit more while zooming, but it's never really a constant zoom with this mode. These tests were handheld, with fairly low light,@ f6.3, 1/60, ISO 1600.