Sony SLT-A99

Preview based on a production SLT-A99 running firmware 1.0

It's been almost four years since Sony released its first full-frame DSLR - the A900. It would be hard for anything to exemplify the subsequent developments in camera technology as effectively as its replacement, the A99 does. Whereas the A900 was a defiantly conventional camera that would have been immediately familiar to Konica Minolta film-camera users, the A99 is something of a technological tour-de-force.

The A900 eschewed futuristic fripperies, such as movie shooting and even live view, that became commonplace not long after its launch. The contrast to the all-live-view, movie optimized A99 couldn't be more stark. And yet, despite the A99's radically different approach, it's a camera that A900 users could pick up and immediately start using (and perhaps even enjoying), thanks to its similar button layout.

key specifications: 24MP full-frame CMOS Sensor with on-chip phase detection AF Fixed-mirror design SLT 2.4M dot OLED electronic viewfinder 14-bit Raw output ISO 100-25,600 Up to 6 frame-per-second continuous shooting with AF ISO-compatible flash hotshoe with 'multi interface' expansion connector Pull-out three-hinge tilt/swivel 1.23m dot RGBW LCD screen Top panel LCD Microphone and headphone sockets Built-in GPS AF Micro Adjust

The A99 is based around Sony's SLT design - a variant on the DSLR concept that uses an electronic viewfinder, rather than an optical one. Instead of having a mirror that has to flip out of the way to to take a photo, it uses a fixed semi-transparent mirror that constantly means light is redirected to a DSLR-style phase-detection autofocus sensor. This means live view and autofocus are always active.

The SLT design means the A99 offers a consistent shooting experience whether you use the flip-out screen or the electronic viewfinder. It also means the conventional 19-point phase detection focus sensor is always illuminated, along with the 109-point on-sensor array. This puts the A99 in the unique position of having dual phase-detection focus systems available at all times - an unusual feature that Sony has developed several features to exploit, including 'depth-map assist continuous AF.'

The ability to access two series of AF sensors and the image data at all times gives the A99 an advantage when it comes to subject tracking, meaning it has a better understanding of where the subject is. Sony has made the most of this by simplifying and speeding-up the method used for locking onto a subject. Now, rather than having to press multiple buttons and risk missing the moment, you can now acquire a subject lock simply half-pressing the shutter button.

The decision to build a full-frame SLT camera will certainly be controversial in some quarters but, based on our experiences with recent models, we think the perceptible advantages of the system tend to outweigh the mainly theoretical disadvantages. Those people willing to spend some time using the A99's electronic viewfinder may well find that the disadvantages they expected, compared to an optical finder, simply aren't as significant as they assumed. Sony's 2.3M dot OLED viewfinder is a pleasure to work with and the approximately 0.4EV light that is redirected to the autofocus sensor is negligible, given how good modern sensors are, in terms of noise.

While we've been encouraged by the improvements made in mirrorless cameras, the technologies they're based on are still in their early stages of development and can't yet compete with the decades of development that have gone into DSLR phase-detection autofocus. As such, while it's quite possible that the SLT design will be looked back on as a stop-gap measure, the other way of interpreting this is that it's the only way of offering this combination of capabilities, using current technologies.

Improved image quality

As well as the additional technologies, Sony has gone to great lengths to stress the work that has gone into improving the camera's image quality. The latest 24MP sensor has been designed so that more of each photosite is light-sensitive. The electronics in front of this light sensitive region have been slimmed-down to increase the angle from which each site can receive light. These changes, combined with a design that provides a short and high-capacity path between the sensor output and the image processor, and the addition of 14-bit Raw output, should mean improved still image quality.

Stills photographers are also likely to appreciate the amount of direct control the camera offers, with three dials and a host of buttons dedicated to a single function (five of which are customizable).

Movie capabilities

When the A900 was launched, there were no DSLRs capable of Full HD capture on the market (the EOS 5D Mark II arrived a week later). In the meantime, it's become a key battleground for large sensor cameras and the A99 makes a fairly strong case for itself.

As well as allowing fast, usable live view and full conventional DSLR behavior, it also provides the most effective autofocus system currently available for video. This combination, in itself, is likely to be enjoyed particularly by photographers wanting to get the most out of their video clips without having to re-train as a video focus puller.

In common with recent Sony models, the A99 can capture movies at frame rates of up to 1080p60 at a bitrate of 28Mbps or 1080i60 at up to 24Mbps. There's also the ability to output uncompressed data to an external monitor or recorder - putting the A99 into competition with Nikon's D800.

The A99 features built-in microphone and headphone sockets, along with 32-step input control and even the option to receive balanced mic inputs through XLR connectors via the 'multi interface' hot shoe. But the big hardware gain for video shooters is the addition of a customizable silent control dial next to the lens, allowing various settings to be controlled without knocking or adding noise to the footage being captured.

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