Review: Sony Alpha SLT-A33L

Camera technology is changing for the better these days. While the digital SLR or DSLR is normally the weapon of choice for the serious or professional photographer, a spate of new cameras has been challenging this notion. The Micro Four Thirds interchangeable lens cameras started it. Micro Four Thirds cameras usually have CMOS sensors, but vitally, the sensor size is smaller than even an entry-level DSLR. Even Sony's own NEX series is another example: a camera that uses a DLSR-size CMOS image sensor in a mirror-less, compact and lightweight body.


Each of these technologies has certain advantages - typically a smaller size and lesser weight as compared to a DSLR. But the Alpha SLT-A33L (and its big brother, A55L) takes things to a new level. The A33 is not much smaller or lighter than the average DSLR, but what it does do, is open up a super-fast continuous shooting mode (with continuous auto focus for each shot) in a price bracket that 'proper' DSLRs can't dream of matching.

A number of ground-breaking technologies enable this. For starters, the translucent mirror. In a conventional DSLR, the mirror stays down at a 45-degree angle to divert light upwards into the viewfinder and to the fast, phase-detection auto focus system. When the shutter button is pressed, the mirror flips up, allowing the light to pass through to the image sensor. This is why the viewfinder in a conventional DSLR goes blank while shooting. Also, the mechanical movement of the mirror is a comparatively slow movement when compared to the actual recording of light, which contributes to the slower frame rate of entry-level DSLRs. In Sony's system, the mirror just stays in place: most of the light passes through to the image sensor, while a portion of the light is diverted upwards towards the autofocus system and to generate an image for the electronic viewfinder (EVF).

Since the mirror is always down, the slow mechanical mirror flip movement is cut out of the equation and the recording of each image can be much faster. In high-speed mode, the A33 can take 7 frames per second at full resolution. Since the mirror stays down, the autofocus engine is always active. Rather unbelievably, the camera can focus each frame while shooting in high-speed mode, i.e., 7 times per second. This kind of frame rate and autofocus speed can only be matched by high-end professional DSLRs that cost thrice as much as the A33.

Crucially, the video recording features are also enhanced by the mirror. Since the AF system is always active, the A33 can continue to focus while shooting video: something which conventional DSLRs cannot do - the mirror has to stays up while shooting video to let light through to the image sensor. Stangely, the A33's video is limited to 1080i rather than 1080p full HD for some reason.