The long-anticipated successor to Sony's original flagship full-frame DSLR (the DSLR-A900, introduced in 2008 and discontinued some time ago) isn't a traditional DSLR. Like the company's APS-C-format SLT cameras, the new full-frame SLT-A99 features Sony's unique TMT (Translucent Mirror Technology) concept, which replaces the DSLR's moving mirror, focusing screen and pentaprism optical viewfinder with a fixed semitranslucent mirror and an eye-level electronic viewfinder.
Translucent Mirror Technology
The Bayer-filtered sensors used in most DSLRs can produce moiré (false colors) when photographing fine patterns, so most have an anti-aliasing low-pass filter on the sensor to combat that. The low-pass filter slightly blurs the image, however. When the pixel count is high enough and the pixels are small enough, the low-pass filter really isn't needed, and sharper images can be obtained without one. So Nikon offers the D800 in two versions: standard D800, with the low-pass filter; and D800E, with a special filter that cancels the anti-aliasing properties. The latter produces even sharper images and costs $300 more.
Replacing the conventional DSLR pentaprism eye-level viewfinder with an electronic viewfinder reduces camera bulk, but the main advantage is that you get convenient eye-level viewing for both still and movie shooting. While electronic viewfinders have historically been inferior to SLR pentaprism finders, especially for low-light and action shooting, the A99 has a latest-generation XGA OLED EVF, with 2,359,000 dots of resolution and quick refresh. We haven't seen the new A99 yet, but the older EVF in Sony's previous top SLT model, the A77, let us do stills and videos of birds in flight. The EVF shows 100% of the actual image area with 0.71X magnification (50mm lens at infinity), has built-in dioptric correction from -4.0 to +3.0 (more than DSLR finders provide) and can display lots of information when you want to see it.
HD Video With Phase-Detection AF
One drawback of HDSLRs is that they have to be in Live View mode to do video, and that means using the external LCD monitor to compose and relatively slow contrast-based AF. The A99's TMT technology provides convenient eye-level viewing and full-time phase-detection AF for both still and video shooting—a tremendous advantage for wildlife videos. While the A99 wasn't available for testing at press time, we were able to do nice videos of birds in flight with last year's A77 model and the Sony 70-400mm G zoom. The A99 can do 1920x1080 full HD at 60p (also 60i and 24p) in AVCHD v2.0 format, plus 1440x1080, 1280x720 and 640x480 MP4 video at 30p, all with stereo sound via a built-in microphone or an external mic.