Sony's latest interchangeable lens cameras, the SLT Alpha A33 and A55 represent a significant technological milestone - not just for Sony but for the enthusiast camera market as a whole.

The company has rejected the traditional DSLR design and instead created a hybrid that, like a compact camera, is from the ground up built around live view, but one that is also capable of offering full-time DSLR-style phase-detection autofocus. The combination means they can offer features such as phase-detection AF during movie recording and extremely fast continuous shooting rates (10 frames per second on the A55), previously unthinkable at this price.

This is made possible by adopting an approach that has more in common with a mirrorless camera (like the Panasonic G2, for example) than an SLR by removing the bits that pretty much define such cameras: the optical viewfinder and moving mirror.

The designation 'SLT' stands for single lens translucent and it's the 'translucent' bit that's the key to what differentiates these new models both from conventional DSLRs and mirrorless interchangeable lens cameras. The SLTs do have mirrors, but they're mirrors that let the majority of the light pass straight through to the sensor, rather than having to swing out of the way to allow exposure. As a result they are fixed in position, always reflecting a portion of the light emerging from the back of the lens onto a phase-detection AF array housed in the top of the camera. (A newly-developed 15-point array in the case of these two cameras).

The A33 features the same 14 million APS HD CMOS sensor as the NEX-3 and NEX-5, but the sensor in the A55 is brand new, with 16.2 million effective pixels - Sony's highest-resolution APS-C format sensor yet. In another first for Sony's large-body interchangeable lens models, both cameras can shoot movie files as well, at 1080p HD resolution. Technically this review was conducted with a SLT A55V: the GPS-enabled variant of the camera that will be sold in most markets - only in a handful of countries (notably Japan), will a non-GPS version of the A55 be sold.

Sony A55 - key specifications

  • 16.2MP (effective) APS HD CMOS sensor
  • Fixed, pellicle-type semi-translucent mirror
  • Maximum ISO 12,800 (with a quasi-ISO 25,600 'Multi-frame NR' option)
  • 15-point phase-detection AF array with 3 cross-type AF points
  • Electronic viewfinder with 1.15 million dot resolution
  • Built-in GPS
  • Electronic level in EVF/LCD with pitch/roll indicator
  • Dual-purpose Memory Stick/SD card slot
  • 10fps continuous shooting rate
  • 1080p AVCHD movie mode with continuous AF
  • Articulated 3in 'TruBlack' LCD with 912k dots
  • socket for external microphone
  • 2x magnification mode in live view
  • Face-detection AF (focus via nearest phase-detection AF point)

Sony A33 and A55 - differences


Sony Alpha A33

Sony Alpha A55
• APS-C 'Exmor' APS HD CMOS sensor
• 14.6 million total pixels
• 14.2 million effective pixels
• RGB (Primary) color filter array
•APS-C 'Exmor' APS HD CMOS sensor
• 16.7 million total pixels
• 16.2 million effective pixels
• RGB (Primary) color filter array
Continuous shooting
• Continuous Advance Priority AE: max 7fps
• Continuous: 6fps
• Continuous Advance Priority AE: max10fps
• Continuous: 6fps
• Built-in - records orientation and elevation data.
Buffer in continuous shooting
• JPEG Fine: 16 frames
• JPEG Standard: 20 frames
• RAW: 7 frames
• RAW + JPEG: 7 frames
• JPEG Fine: 35 frames
• JPEG Standard: 39 frames
• RAW: 20 frames
• RAW + JPEG: 20 frames
Battery life (approx - CIPA)
• EVF: 270 images
• LCD: 340 images
• EVF: 330 images
• LCD: 380 images
Weight (body only)