They may look like smaller versions of traditional SLRs, and even accept the same lenses as their true DSLR counterparts, but cameras like the Sony NEX-5, NEX-3 and NEX-C3, the Panasonic Lumix DMC-G3 and the Samsung NX10 are a different breed. Instead of including an optical viewfinder and a swiveling mirror, these cameras feature a high-resolution electronic viewfinder (EVF) with no swiveling mirror. The space saved by losing the mirror and viewfinder optics allows camera designers to make a smaller camera and circumvent a few of the problems found in true DSLRs. Although the NEX-5, NEX-3, NEX-C3, Lumix DMC-G3 and NX10 utilize contrast detection AF technology, the AF system never loses track of the subject.
Sony also has introduced a series of cameras with stationary translucent mirrors that don't swing out of the way to take a picture or shoot video. The Alpha A55, A35 and A33 channel a percentage of the light to a phase detection AF sensor while the remainder lands on the image sensor. Phase detection is a faster AF method than contrast detection AF, and it's potentially even faster than DSLR phase detection AF because the AF sensor is never blocked, but some low-light sensitivity is lost due to the redirected light. Using the phase detection AF system full time makes these cameras particularly quick-focusing in video mode.
Electronic viewfinders used to be frustrating to use in low light and with moving subjects, but improvements have mitigated those shortcomings, and these EVF cameras have some considerable benefits beyond video shooting. In all of the EVF cameras, the fully electronic viewfinders allow you to monitor and change exposure settings, and even play back images and videos without ever taking your eyes from the viewfinder. EVFs also can mimic under- and overexposures before you take the picture. They're definitely worth a look.
Michael J. McNamara has decades of experience in imaging technology. See more of his reports on trends and technologies on his McNamara Report website at www.mcnamarareport.com.