Overall Performance

The SLT-A99 is a quick and responsive camera in nearly every facet of its operation - as you'd hope for a model at this cost. With a wealth of logically placed external controls, as well as onscreen Fn and Quick Navi menus, you're not likely to be more than a button press away from altering any shooting setting. And the ability to customize as many as five hardware buttons means that by spending a little time at the outset, you can have a camera that operates exactly as you want it.

We're also happy to report that the A99 avoids the operational pitfalls of previous Sonys, like the SLT-A77, which have been prone to delays when showing or zooming a playback image. The A99 is much improved in this regard - the review image appears immediately (though there's a slight delay before the effects of DRO are applied), and the lag between pressing the zoom button and the camera responding is very slight.

The only operational aspect of the A99 we'd characterize as slow is the time the camera takes to capture an exposure upon first powering up. It can take as long as two seconds from power-on to first exposure with the camera in MF mode. By contrast, even mid-range DSLRs can capture an initial image in about 0.5 seconds. During this delay on the A99, you see the screen populate with aperture and shutter speed information and the SD card slot access lamp briefly flash. Waking the camera from sleep to capture an image triggers this same routine, and takes about two seconds as well.

The A99 features dual SD card slots and a number of storage configuration options. You can record both stills and video to the same card slot (the default behavior) or designate a card slot to each media type. You can record stills and/or video simultaneously to both cards, for a real-time backup. You can also choose to specify one card slot for stills and the other for video. And when shooting in RAW+JPEG mode, you can also designate a specific card slot to record either file format.

SLT features

One of the biggest appeals of the fixed-mirror SLT design is that the camera doesn't need to wait for its mirror to get out of the way before it can make an exposure, so frames can be captured at a maximum rate governed by the speed of the shutter mechanism. Ultimately, it is easier and cheaper to build a shutter which opens and closes 10 or 12 times per second than it is to make a mirror which has to be raised and lowered at the same rate. Those cameras which can manage it, like the Canon EOS-1D X or the Nikon D4, are very costly. By default, the A99 enables electronic first curtain shutter mode. It's an idea we've seen on Sony's recent SLTs and NEXs (along with Canon DSLRs dating back to the EOS 40D) - rather than closing the shutter then opening it again to start the exposure, the camera keeps the shutter open and begins the exposure by starting to read the information off the sensor, one line at a time. The exposure is then ended when the physical shutter travels down across the sensor, blocking off the light. The result is a shortening of the time lag between pressing the shutter button and the exposure being made.

Continuous Shooting and Buffering

The Sony A99 has two continuous shooting methods - the full resolution Continuous drive mode available from most shooting modes and the faster, but more automated, 'Tele-zoom Continuous Priority AE' shooting mode, selected from the mode dial. The Continuous Hi drive mode provides 6 fps shooting and is available in any of the JPEG or Raw settings. It is only at the Continuous Lo setting of 3 fps, however, that live view is available while shooting. The 'Tele-zoom' crop modes allow up to 10 frames per second, depending on the how small a crop you specify. The options are a 10.3MP (1.5x crop) image at 8 fps or a 4.6MP (2.4x crop) image at 10 fps. You can shoot Raw images in the 8 fps mode, whereas the faster 10 fps mode is JPEG-only.

Continuous Advance Priority AE T10 (4.6MP 2.4x crop)

JPEG Large/XFine
JPEG Large/Fine
Frame rate 10.0 fps 10.0 fps
Number of frames 17 18
Buffer full rate 4.5 fps 7.0 fps
Write complete 4.5 sec 4.0 sec

As you can see, shooting at the JPEG 'extra fine' setting significantly slows down the shooting rate once the buffer is full, compared to the JPEG Fine option.

Continuous Advance Priority AE T8 (10.3MP 1.5x crop)

JPEG Large/XFine
Frame rate 8.0 fps 8.0 fps 8.0 fps
Number of frames 19 21 20
Buffer full rate 3.0 fps 2.8 fps 2.3 fps
Write complete 6.5 sec 6.5 sec 8.0 sec

Reducing the rate to 8 fps allows a slightly higher capacity before the buffer becomes full. The major benefit though, by far is the ability to shoot Raw files. This 1.5x crop mimics the field of view of an APS-C camera like the A77, albeit at a lower resolution.

Continuous Hi

JPEG Large/XFine
Frame rate 6.0 fps 6.0 fps 6.0 fps
Number of frames 20 17 13
Buffer full rate 2.5 fps 1.8 fps 1.5 fps
Write complete 5.0 sec 7.5 sec 8.5 sec

In full resolution mode, the maximum shooting speed is 6 fps for both JPEG and Raw files. This is on par with the performance of similarly priced DSLRs. The most impressive numbers here though are the very short write times for the A99. When compared against DSLRs of similar resolution like the 22MP Canon EOS 5D Mark III and 24MP Nikon D600, the A99 empties its buffer more than twice as fast for JPEG and Raw files.

All timings performed using a 16GB SanDisk Extreme Pro UHS-I SDHC card (45MB/s)

Frame 1 Frame 2 Frame 3 Frame 4 Frame 5 Frame 6

As you can see in the six-shot sequence above, a 6 fps shooting rate is useful for capturing fast action. As we'll discuss on the AF performance page of this review, however, that's only part of the equation for sports photography, with focus tracking being of even more importance.

SteadyShot image stabilization

Sony's in-camera image stabilization system, dubbed SteadyShot, is a incarnation of technology that dates back to the Konica Minolta days and is well-established throughout Sony's line of Alpha cameras. Sony typically claims between a two and four-stop benefit and in real-world use we've found this to be a reasonably accurate claim. The benefit of a sensor-based stabilization system, is of course, that it's available regardless of which lens you have mounted on the camera. This stands in comparison to Nikon and Canon, both of whom offer lens-based image stabilization.

50mm, 1/10 sec. @ f/5.6, ISO 800 100% crop

The image above was shot handheld at a 50mm focal length with SteadyShot enabled. As you can see, shooting at 2 1/3 stops EV below the traditional 1/focal length guideline still results in a critically sharp photo. This means that you can use a lower ISO sensitivity, reaping the benefits of lower noise, without sacrificing sharpness.

Battery life

The A99 uses the familiar 11.8Wh NP-FM500 battery, the same one we've seen in previous Alpha models, including the A900. With a CIPA standard capacity of 410 shots using the EVF, it provides less than half the shooting capacity of the A99's rivals; a direct consequence of having to support full-time live view.

In our daily use with the camera, we were able to go on a reasonably full day of predominantly still-image shooting and return with a battery that still held some charge. Of course on multi-day photo-specific journeys you'd be best served by carrying a spare, should you neglect to fully recharge a battery at the end of the day. But for many local shooting situations, we suspect many photographers will carry on just fine with a single fully charged battery.