Once again Sony is reworking an already tried idea and claiming it as its own (the last time it did this was with the dual-sensor live view DSLRS, actually pioneered by the Olympus E-330), and once again we’ll probably let them get away with it because what they’re doing is admittedly quite cool. This time they’re reviving an idea Canon apparently tried in the 60′s of using a semi-transparent mirror. The idea was a third of the light went through the viewfinder, and 2/3 through to the film, and the mirror didn’t have to flip. It also meant the viewfinder was dark and the shots needed 1/3 stop more exposure, but hey, kudos for trying.

The Sony is a bit different. As you might know, Sony’s goal has been to make live view as seamless a process as possible, and they’re dedicated to bringing the faster, mirror-requiring phase detect auto-focus speeds to a system that normally requires the use of slower contrast-detect. Their first solution was the previously mentioned dual sensors. If you turned on live-view it shifted the mirror to bounce the light not through the viewfinder, but onto a secondary imaging sensor for live-view output. This allowed the mirror to continue bouncing part of the light into the same auto-focus sensor the camera used in regular mode.

This new solution uses a mirror that’s mostly transparent, it’s only enough of a mirror to redirect enough light into the auto-focus sensor for it to work. The rest barrels straight through the mirror and onto the sensor. This means that an optical viewfinder isn’t possible, and Sony gets around this by using a new time-multiplexed electronic viewfinder with a resolution equivalent to 1,152,000 dots (Canon and Nikon’s high-end offerings only have 921,000 dots on their 3″ screens, for comparison). What you’re left with is an SLR style camera with full-time Live View and full-time phase-detect auto-focus. Sony’s calling the tech “SLT” or “Single Lens Transluscent.” Sounds good to us.

So, these SLTs are neat in concept, and Sony doesn’t let it slide to gimmick by backing them with a host of the usual DSLR features. The A55V will have a 16 megapixel sensor, a GPS module, and thanks to that non-flipping mirror it can shot those 16mp images at 10 frames a second. (There’ll be an A55, too, we hear, but not in the US, and it won’t have the GPS). The A33 is only a paltry 14 megapixels, no GPS, and can only crank along at 7 frames per second. They both use those high-end EVFs, and both sport 3″ 921,000 dot center-hinged tilt-swivel LCDs on the back. And of course they have SteadyShot sensor-shift image stabilization.

The SLT tech also lets them have full 1080i HD movies modes with full-time auto-focus, so that’s a win.

They’ll both also feature those shiny new Sony features the high end compacts and NEX cams have been using, like Sweep Panorama, 3D Sweep Panorama, Auto HDR, and Handheld Twilight modes.

They’ll record to Memory Stick or the much more reasonable SD/SDHC/SDXC.

These two models will reportedly start shipping sometime in October, the A55V will be $750 body only, $850 with an 18-55. The A33 will be $650 body only, $750 with 18-55mm.