Sony's Live View system is the most effective currently available. Matt explains what makes it different.
If you’ve bought a DSLR in the last couple of years, chances are that you’re able to view a live preview on its LCD screen. Breaking shooting tradition somewhat, this is still something many people are wary of but depending on your model it can enable high- and low-level shooting and aid precise focusing, broadening your shooting possibilities. Sony currently boasts the most fluid and effective live view system, as seen on its A380, A450, A500 and A550. So how does it work?
The first thing to understand is that not all systems utilise the technology in the same way. Sony’s models feature a secondary sensor inside their viewfinder chambers, to which light is directed by a corresponding tilting mirror. Until the light enters the viewfinder it follows the same path, so the camera’s main mirror stays put to direct the light accordingly. This means light can reach the AF sensor, thus allowing autofocus for both viewfinder and live-view shooting to be employed in the same way. It’s only when one of the mirrors inside the viewfinder is instructed to tilt that it feeds the light to the dedicated live view sensor, relaying it on the LCD screen.
The idea of using of a secondary sensor in the viewfinder chamber isn’t something Sony can take credit for, though, as it follows a similar system first seen in Olympus’s E-330 – the first DSLR to offer full-time live view. Subsequent Olympus models have built on this, incorporating an Imager AF mode, using both phase and contrast detection, to aid autofocus, though Sony still has the edge in terms of speed and usability. Other DSLRs don’t have a secondary sensor inside their viewfinder chambers and consequently require their mirrors to lift once live view is activated. This means either the mirror needs to momentarily flip back down to autofocus or, if the option is available, to use contrast detection, which is generally much slower.