Overall Performance

The A57 is a very responsive camera in terms of operational handling, displaying none of the sluggishness we occasionally experienced with its predecessor, the SLT-A55. Browsing through the multi-tabbed main menu interface is admittedly a bit tedious, but you can move very quickly through options using either the 4-way controller or front dial.

As you can see in the table that follows, write times are quite reasonable and even more importantly, you can navigate through the menu system, and continue shooting (at a reduced frame rate) while data is being off-loaded to the SD card.

Of course when you talk about the A57's performance, the spec that gets people's attention is its maximum frame rate. The SLT-series' unique fixed mirror design allows for an exceptional maximum full resolution frame rate of 10 fps. While this does come with some limitations (as you can read about in more detail below), it remains a benchmark of entry-level DSLR performance. And a generously sized buffer means that you can shoot maximum frame rate image bursts of at least 18 captures even in Raw+JPEG mode. Very impressive indeed.

Continuous Shooting and Buffering

The SLT-A57 has three full resolution continuous shooting modes, 'Lo','Hi' and 'Continuous Advance Priority AE'. In continuous 'Lo' mode the A57's nominal frame rate is 3fps, which increases to 8fps in 'Hi' and 10fps in 'Continuous Advance Priority AE' mode. In addition, there is a Tele-zoom continuous priority AE shooting mode which has a maximum of 12 fps, but this does involve a 1.4 crop of the imaging area, yielding an 8.4MP file versus normal 16MP output.
The A57's maximum framerate of 12fps can be achieved in a special mode found on its exposure mode dial. The 'T' designates 'tele zoom' which utilizes a smaller area of the sensor, giving an effective crop factor of 1.4X.
The 'AE' in Continuous Advance Priority AE mode stands for 'automatic exposure'. Unlike continuous Lo and Hi, Continuous Advance Priority AE can only be accessed via the exposure mode dial. As we saw in the A55, which offered a maximum frame rate of 10fps in the same mode, there are some downsides to this maximum capture rate. The A57 can still autofocus continuously, but in order to be able to do this, aperture is either fixed wide open, or limited to f/3.5 if the lens's maximum aperture allows. You can take full control over aperture in Continuous Advance Priority AE mode, but only if you select AF-A or manual focus. The reason for this limitation is the same reason why you cannot combine AF with manual aperture control in movie mode - at apertures smaller than f/5.6 the AF system receives essentially no light, so cannot function.

Another disadvantage of the SLT system when it comes to fast shooting is that it isn't possible for the A57 to maintain a live view feed in 8, 10 or 12fps capture modes. The viewfinder does not black out when shooting at these high frame rates, but shows a sequence of still frames you've just shot. What this means is that at any given moment, you don't see the current view through the camera's lens, but how it was a fraction of a second ago. This makes little or no difference if you're shooting slow-moving or static subjects, but it makes panning with fast-moving subjects very hard indeed, since you never know quite where they are - only where they were.

Continuous Advance Priority AE

JPEG Large/Fine
Frame rate 10.0 fps 10.0 fps 10.0 fps
Number of frames 22 20 18
Buffer full rate 2.5 fps 1 fps 0.7 fps
Write complete 8 sec 21 sec 23 sec

Continuous Hi

JPEG Large/Fine
Frame rate 8.0 fps 8.0 fps 8.0 fps
Number of frames 25 21 18
Buffer full rate 2.2 fps 0.9 fps 0.7 fps
Write complete 7 sec 20 sec 21 sec

Continuous Lo

JPEG Large/Fine
Frame rate 3.3 fps 3.3 fps 3.3 fps
Number of frames 72 26 22
Buffer full rate 2.5 fps 0.9 fps 0.7 fps
Write complete 7 sec 18 sec 21 sec

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

One of our biggest criticisms of the original SLT-A55 was its lengthy buffer times after shooting continuous bursts of images - up to around 50 seconds depending on the file type. As you can see, with our current UHS-I SDHC test memory card, the A57 performs much better, with a maximum write time of less than half that. And as we mentioned earlier, you can access the menu system and shoot at a reduced rate while data is written to the card. Make no mistake, though, if you're in the field trying to catch fleeting action or sports, waiting even 20 seconds to resume shooting at the top frame rate is a disadvantage. But for more casual photo opportunities, like kids' parties or group portraits, this level of performance certainly makes it easier to capture pleasing facial expressions.

Autofocus speed / accuracy

When photographing static and slow-moving subjects we found the AF system to work quickly and accurately. Out of focus examples were rare among our several hundred sample shots.

As you can see in the 100% crop on the right, subjects of moderate speed, moving along a consistent path can be rendered in good focus. In shooting scenes such as this one, we commonly came away with a hit rate of 5-6 out of 10 shots.

Fast-moving subjects, are much more of a challenge, however. While you can capture 10fps in the camera's continuous AE priority mode, you shouldn't expect a 100% hit rate. At anything more demanding than a leisurely cycling pace along a straight line, the A57 can struggle to accurately predict subject position at relatively close range.

We don't want to be too harsh though. As you can see in the sample above, for everyday use - and in comparison to its DSLR peers - the A57's AF is more than capable. We would simply caution that while it has a frame rate that nearly matches a pro DSLR like the Canon EOS-1D X, other factors like advanced predictive tracking, customizeable AF modes and not least, the ability to view the live scene (versus the image you've just captured) while shooting are just as important for those who photograph fact action for a living.

SteadyShot image stabilization

The A57 uses sensor-based image stabilization, dubbed 'SteadyShot'. The obvious benefit of an in-body IS mechanism is that you can take advantage of it with any lens attached, as opposed to the lens-based approach of both Canon and Nikon which require specific IS-enabled lenses.

ISO 800, 1/25 sec. f/5, 60mm (equiv.) In this 100% crop you can see that with SteadyShot enabled, you can get a usably sharp image at 1 1/3 stops EV below the 1/effective focal length guideline.

We've done extensive testing of Sony's SteadyShot capabilities and found that it offers at a 2-3 stop EV advantage across a range of shutter speeds. This means you can shoot at shutter speeds well under the 1/effective focal length rule and consistently come away with acceptably sharp images. You can read our detailed test results in our Sony SLT-A55 review.

Battery life

The A57 - using the same battery found on the A65 and A77 - has significantly improved battery life over its predecessor, the A55. Sony's lists CIPA measurements between 550-590 images depending on EVF or rear LCD usage. Although performance obviously varies with conditions, our real-life use of the camera was largely in line with these numbers. We were consistently able to make it through a full day of shooting both still images and short duration videos, with frequent image reviewing, with at least some power left in the battery. For multi-day shooting excursions, a second battery would of course be helpful, but taking a single battery and simply charging it overnight will be enough to guarantee enough juice for most shooting excursions.