The A300 may be average in terms of size and weight, but it does have something that makes it stand out of the crowd: Live View with fast auto-focus. None of the currently manufactured competitor models – the ‘non-SLR’ Panasonic Lumix DMC-G1 aside – can auto-focus quickly in live view mode, and that’s because they get the live view feed off the main imaging chip, which means their mirror must be raised while in this mode, blocking light from reaching their AF sensors.
Sony have circumvented this problem by using a secondary sensor. The idea isn’t new – the very first DSLR to sport continuous full-colour live view, the Olympus E-330 of 2006, had two live view modes, one of which, labeled ‘Mode A’, also made use of a second imaging chip. This allowed the use of fast phase-detect auto-focus and did not introduce any extra shutter lag. The catch was that this solution did not provide anywhere near 100% field coverage and left the optical TTL viewfinder – one of the most important parts of any SLR – dim and small.
