Apart from the translucent mirror technology changing the implementation of phase-detection AF, the AF sensors themselves are a completely new design. There are 15 AF sensors in total, of which three are cross-type sensors, which are faster and more accurate.
In use, I found the AF of the Alpha 33 is faster than on previous Sony DSLRs. Automatic focusing is swift and feels comparable to similarly specified Canon and Nikon DSLRs, such as the Canon EOS 1000D and Nikon D5000.
Of course, it is when the phase-detection AF and translucent mirror are combined with the fast shooting rate that the camera is at its most impressive. For instance, when photographing a cyclist heading straight towards me at around 15mph, the AF system maintained its 7fps shooting rate, resulting in the cyclist being in focus in each shot. I also photographed a car travelling at around twice the speed of the cyclist, and again the AF was able to keep pace.
While the build quality and control of the camera may not be of a professional standard, the AF and shooting rate combination is. The combined speed opens up a number of new possibilities for entry-level and enthusiast photographers that previously would only have been available to those with £1,000 or more to spend on a DSLR.
The AF shines in bright conditions, but I was curious to see how the camera would perform in low-light conditions, such as those found at a concert. Although the system was a little slower, it was still impressive and was able to focus even when the bright spotlights weren’t on the performer.