While Sony’s 24.3-million-pixel, full-frame Alpha 99 has a glittering specification on paper, the true test is how the camera handles a number of demanding situations in the field. Read the Sony Alpha 99 review...

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Sony Alpha 99

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Sony Alpha 99 review

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£2,299.00
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Sony Alpha 99 review – Autofocus

This diagram shows the 19-point phase-detection AF sensor array and the 102-point focal-point array. Sony claims the latter covers 30% of the frame

Sony has introduced some interesting changes to the autofocus set-up of the Alpha 99. It uses a dual phase-detection autofocus system. Like the Alpha 77, the phase-detection AF sensor is made up of 19 points, 11 of which are the more sensitive cross type. These 19 points are grouped together in a small central portion of the frame. For quick and successful focusing across a number of situations and light conditions, it is key for the subject to be covered by the cross-type points. There is a further focal-point sensor with 102 points that is built into the imaging sensor and has an approximate 30% coverage of the frame, which is impressive.

To complement the new dual AF set-up, an AF-D mode has been introduced, which uses both systems. This mode works well with object tracking for fast-moving subjects such as football players, but also for landscapes or subjects that are off-centre as the AF point coverage is wide. It should be noted that the dual AF is only available with six current lenses, including the Carl Zeiss 24-70mm f/2.8 lens used in this test, although Sony promises firmware upgrades for more lenses.

A handy feature is the new AF range control, which offers manual control of the minimum and maximum focus distance. There are a couple of benefits to limiting the focus range – subjects nearer to or further away from these distances do not confuse the AF system, and there is less distance for the camera to scan for a focus point, which means quicker focus in low-contrast light.

For subjects in the centre of the frame, the Alpha 99 performs excellently. I do, however, find the limited coverage of the 19 points to the centre portion of the frame more restrictive for spot focusing.

  1. 1. Sony Alpha 99 at a glance:
  2. 2. Sony Alpha 99 review - Features
  3. 3. Sony Alpha 99 review - High speed shooting
  4. 4. Sony Alpha 99 review - Build and handling
  5. 5. Sony Alpha 99 review - White balance and colour
  6. 6. Sony Alpha 99 review - Metering
  7. 7. Sony Alpha 99 review - Noise, resolution and sensitivity
  8. 8. Sony Alpha 99 review - Autofocus
  9. 9. LCD, viewfinder and video
  10. 10. Dynamic range
  11. 11. The competition
  12. 12. Our verdict
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