Video capture in DSLRs is a really cool idea—until you try to focus while shooting it. The footage may be fine, but there’s that mirror in the way of the sensor. Flip the mirror up for video, and you lose better-performing phase-detection autofocus. So Sony adapted some old tech—a nonmoving, semitransparent mirror—to allow some light to go to the AF sensor during shooting. It’s a workaround that works, and it also gives you up to 10-fps still shooting.