Sony Alpha 55 at a glance:

  • 16.2 million effective pixels
  • 10fps continuous shooting with AF
  • Built-in GPS
  • Electronic viewfinder
  • Full 1080i HD video
  • 1,200-zone evaluative metering system
  • Street price £669 (body only)

It is proving to be a big year for Sony as it has branched out from its conventional DSLR Alpha range into more alternative interchangeable-lens cameras. In May, it added the NEX-3 and NEX-5 micro-system cameras (MSCs) to the Alpha range, and just months later in August it revealed the Alpha 560, 580 and Alpha 33 and 55 models. Sony describes the latter two not as DSLRs, but as single-lens translucent (SLT) cameras.

What distinguishes the Alpha 55 and 33 SLT cameras from DSLRs is that they employ translucent mirror technology (TMT), which uses a fixed pellicle mirror rather than a moving mirror. TMT works by allowing 70% of light to pass through the mirror to the sensor, while reflecting the other 30% onto the phase-detection AF sensor. This means that the phase-detection AF system has uninterrupted exposure to light, which makes it constantly available even while the shutter is open.

This should improve the response, handling and functionality of the AF system.

By using translucent mirror technology, Sony can claim another first for its Alpha range. While a moving mirror used in DSLRs must lift with each exposure, the translucent mirror is fixed and, as a result, the shooting rate can be increased.

The Alpha 55 boasts ten frames per second while maintaining full AF, which is the fastest frame rate of any camera at this level – and for a price of just £700. Prior to the release of the Alpha 55, only the Canon EOS-1D Mark IV could claim a continuous shooting rate of 10fps with AF, while the Nikon D3S boasts 9fps.

However, these cameras cost in the region of £3,500, which is almost £3,000 more than the Alpha 55. It will be interesting to see whether the Alpha 55’s image quality can match the fast frame rate, how reliably the AF performs in this mode and how these aspects compare to the more expensive models.

Sony now boasts a comprehensive range of Alpha cameras that share many features, and it is becoming increasingly difficult to ascertain which camera is targeted at which group of photographers.

With the Alpha 55 costing just £100 more than the Alpha 33, one key point for buyers to consider is how much extra the Alpha 55 offers and whether this merits spending the extra cash. Has Sony created enough differences in the features and performance of both cameras to clearly distinguish between them and to appeal to two different levels of photographer?

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