VIDEOCompact digital cameras have had low-res video capability almost from the start, and a number of newer compacts and most DSLRs introduced in recent years offer HD (720) or even full HD (1080) video capability. The mirrorless cameras all offer HD video, most providing full HD. The newest Nikon, Olympus, Panasonic and Sony models offer the most advanced video capabilities, including usable continuous autofocusing while shooting, something lacking in the HD-capable DSLRs (except Sony's Translucent Mirror models, which provide phase-detection continuous AF during video shooting). Bear in mind that built-in microphones will pick up the sound of the AF motor.
As is the case with DSLRs and compact digital cameras, the mirrorless models were designed primarily for still photography, and aren't meant to be replacements for serious dedicated digital camcorders. But they can turn out great video clips, which adds motion and sound to your creative photographic arsenal. And their larger image sensors and interchangeable lenses provide more depth-of-field control and flexibility than the affordable camcorders.
WHICH ONE IS FOR YOU?To determine which is better for you—mirrorless or DSLR—you have to consider your own photography. As far as image quality is concerned, the top mirrorless models can match that of the top APS-C DSLRs. Mirrorless cameras are much smaller and lighter, making them easy to carry for long periods, and easy to use inconspicuously.
DSLRs are better balanced with longer lenses, and better suited for action photography. All DSLRs have convenient eye-level viewfinders, while some mirrorless cameras don't. Mirrorless cameras that do have electronic viewfinders often aren't as good as the finders on midrange DSLR cameras (some feel the EVFs are better than the pentamirror finders of many low-end DSLRs—check this out for yourself before buying either camera type).
The mirrorless interchangeable-lens cameras are rapidly gaining market share, and not just among casual photographers, so, obviously, they're just what many photographers are looking for: truly compact cameras that make top-quality images.
When An SLR Isn't An SLR
The traditional single-lens-reflex camera contains a reflex mirror set at a 45° angle. When light from the lens hits the mirror, it's reflected up to a focusing screen, then on to the pentaprism (or pentamirror, in lower-cost cameras) and delivered to the viewfinder eyepiece. When you press the shutter button to make a shot, the mirror flips up out of the light path, so the light can reach the image sensor (or film, in a 35mm SLR). The mirror then drops back down to the viewing position once the exposure has been made.
Sony's SLT cameras look just like DSLRs, and contain a 45° mirror like DSLRs. But the mirror doesn't move. It's semi-translucent, transmitting most of the light to the image sensor while reflecting a portion of it up to a phase-detection AF sensor. This system allows the camera to use the quick phase-detection AF system all the time—even during video recording. In fact, the Sony SLTs are the only DSLRs that provide continuous phase-detection autofocusing for video. The nonmoving mirror also does away with the SLR's brief viewfinder blackout during exposure, and the vibration caused by the mirror flipping up and down.
Instead of an SLR's eye-level optical finder, the Sony SLT cameras use an eye-level electronic viewfinder—a very high-resolution OLED one in the top SLT-A65 and SLT-A77 models. Historically, electronic viewfinders have not been as good as SLR optical finders, especially for action or in dim light, but the Sony OLED finder is a big step in the right direction.
Since the SLT cameras are in live-view mode all the time, that takes a toll on battery life. While battery life is less than that of a DSLR, it's better than that of a typical compact camera, and it's easy enough to carry a spare battery or two (something you should do with a DSLR, as well).