Sony SLT-a99

24.3MP full-frame CMOS sensor | Sony dual AF system with translucent mirror | Steadyshot image stabilization 

What we like:

  • Phase-detect AF in video
  • Good object tracking
  • In-body IS works with all lenses

What we don't:

  • Worse ISO performance than peers
  • Small AF area coverage, with limited lens compatibility for extra AF points 
  • Phase-detect AF not compatible with manual exposure control in video mode
  • No histogram in video mode 

The Sony SLT-a99 is Sony's flagship full-frame interchangeable lens camera, and nominally replaces the A900, which was released all the way back in 2008. It uses Sony's 'SLT' design with a 2.3M dot OLED electronic viewfinder, and has a fully-articulated 1.2M dot 3" rear LCD. Its in-body image stabilization system works with all lenses, new or old.  

"Its in-body image stabilization system works with all lenses, new or old."

The a99 features an excellent, though at this point dated, 24MP 36x24mm CMOS sensor. While the a99 has good Raw dynamic range, its low light, high ISO performance falls to nearly the bottom of the pack, falling well behind full-frame peers and even performing worse than some APS-C cameras. This isn't too surprising, though, given the loss of light caused by the SLT design.

The a99's image sensor features on-sensor phase detection, creating a dual AF system with 19 points in a dedicated PDAF module, and 102 on-sensor PDAF points that work in concert for improved focus tracking and precision. The a99's SLT design means the image sensor can be used for scene analysis and subject tracking, telling the AF system what to focus on and how to stick to the desired subject. And since there's no mirror flipping out of the way when a shot is taken, the dedicated PDAF module doesn't experience constant blackouts during continuous shooting, which helps it maintain focus on moving subjects quite well amidst bursts. Unfortunately, both the 19- and 102-point AF points (the latter only work with certain lenses) have fairly limited AF area coverage, and anything that falls outside of these areas will not be focused upon. 

Due to its SLT design, the a99 offers phase-detect autofocus in video for more confident focus, with lessened risk of hunting during focus compared to contrast-detect AF. Your aperture range is severely limited though if you're using AF in video. The a99 also includes Sony's Quick Navi interactive status panel and a host of other features for video shooters, including a 'silent' control dial, mic and headphone sockets, and focus peaking, to make the most of its 1080p60 HD video capability.

Studio Test Scene | Specifications Compared

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