Sony Alpha A99

Generally excellent performance, but sluggish power-off and mode switching.

Startup/Shutdown
Power on to first shot	~0.7 second	Time it takes to turn on and capture a shot.
Shutdown	~2.1 seconds	How long it takes camera to turn off before you can remove the memory card.
Buffer clearing time	8 seconds after 17 Large/XFine JPEGs*	Worst case buffer clearing time. -- This is the delay after a set of shots before you can remove the card.
	7 seconds after 18 RAW files*
	9 seconds after 13 RAW+ Large/Fine JPEG files*
*Note: Buffer clearing times measured with a SanDisk Extreme Pro 95MB/sec UHS-I SDHC card. Slower cards will produce correspondingly slower clearing times. Slow cards may also limit length of bursts in continuous mode. ISO sensitivity and noise reduction settings can also affect cycle times and burst mode performance.

Startup time is fair for its class, but shutdown time is a bit slow. Buffer clearing times are decent with a fast 95MB/s UHS-I compliant card, though buffers aren't very deep.

Mode Switching
Play to Record, first shot	~1.1 seconds	Time until first shot is captured.
Record to Play	~1.7 seconds	Time to display a Large/XFine JPEG file immediately after capture.
Display recorded image	~0.7 second	Time to display a Large/XFine JPEG file already on the memory card.

Mode switching performance is a bit sluggish for its class, though displaying a previously captured image is reasonably fast.

Shutter Response (Lag Time)
Full Autofocus Single Area (center) AF	0.127 second	Time from fully pressing shutter button to image capture. (All timing measurements made with a Sigma 70mm f/2.8 lens)
Full Autofocus Wide Area AF	0.125 second	Time from fully pressing shutter button to image capture.
Continuous AF	0.153 second	This mode usually shows no speed increase with our static subject; we have no way to measure performance with moving subjects.
Manual focus	0.081 second	For most cameras, shutter lag is less in manual focus than autofocus, but usually not as fast as when the camera is "pre-focused."
Pre-focused Electronic first curtain enabled	0.055 second	Time to capture, after half-pressing and holding shutter button. (Electronic first curtain shutter enabled by default.)
Pre-focused Electronic first curtain disabled	0.108 second	Time to capture, after half-pressing and holding shutter button. (Electronic first curtain shutter disabled.)

Looking at the Sony A99's ability to determine that it's in focus when shooting the same target multiple times, its autofocus speeds are very good. The SLT-A99 requires only 0.127 second to autofocus and capture an image using the center focus point. This decreases slightly to 0.125 second in wide-area AF mode. Continuous autofocus lag time is actually a bit slower at 0.153 second, but manual focus is faster at about 0.081 second.

When prefocused with electronic first curtain shutter enabled (default), shutter lag is 0.055 second which is very good for its class, though not quite as fast as the fastest professional DSLRs we've tested. With electronic first curtain shutter disabled, prefocused shutter lag increases to 0.108 second, which is slower than most DSLRs. The Sony A99 user manual recommends disabling it in the following scenarios: a) to avoid "ghosting of a blurred area" when you shoot at high shutter speeds with a large aperture lens, b) when using Minolta/Konica Minolta lenses, and c) to avoid uneven brightness across the image when shooting with high shutter speeds in certain situations.

Cycle Time (shot-to-shot)
Single Shot mode Large Extra Fine JPEG	0.50 second	Time per shot, averaged over 20 shots.
Single Shot mode RAW	0.56 second	Time per shot, averaged over 20 shots.
Single Shot mode RAW + L/F JPEG	0.58 second	Time per shot, averaged over 20 shots.
Early shutter penalty?	No	Some cameras refuse to snap another shot if you release and press the shutter too quickly in Single Shot mode, making "No" the preferred answer.
Continuous mode Large Extra Fine JPEG	0.17 second (5.90 frames per second); 17 frames total; 8 seconds to clear*	Time per shot, averaged over buffer depth of 17 shots, then slowed to an average of 0.55 second, or 1.81 fps.
Continuous mode RAW	0.17 second (5.88 frames per second); 18 frames total; 7 seconds to clear*	Time per shot, averaged over buffer depth of 18 shots, then slowed to an average of 0.52 second, or 1.92 fps.
Continuous mode RAW + L/F JPEG	0.17 second (5.88 frames per second); 13 frames total; 9 seconds to clear*	Time per shot, averaged over buffer depth of 13 shots, then slowed to an average of 0.73 second, or 1.36 fps.
T10 Tele-zoom Cont. Priority AE Small Extra Fine JPEG	0.10 second (9.95 frames per second); 23 frames total; 5 seconds to clear*	Time per shot, averaged over buffer depth of 23 shots, then slowed to an average of 0.24 second, or 4.22 fps with a lot (~39%) of variation.
T8 Tele-zoom Cont. Priority AE Medium Extra Fine JPEG	0.13 second (7.97 frames per second); 23 frames total; 6 seconds to clear*	Time per shot, averaged over buffer depth of 23 shots, then slowed to an average of 0.34 second, or 2.94 fps.
Flash Recycling	N/A	Flash at maximum output.
*Note: Buffer clearing times measured with a SanDisk Extreme Pro 95MB/sec UHS-I SDHC memory card. Slower cards will produce correspondingly slower clearing times. Slow cards may also limit length of bursts in continuous mode. ISO sensitivity and other settings such as DRO or NR can also affect cycle times and burst mode performance.

Shot-to-shot cycle times are fair, at 0.5 second for Large/XFine JPEGs increasing slightly to 0.56s for RAW and 0.58s for RAW+Large/Fine JPEGs.

Full-resolution continuous mode speeds are good for a high-resolution full-frame camera, at about 5.9 frames-per-second no matter the file type.

The Sony A99 also offers two cropped modes with faster burst rates. T10 Tele-zoom Continuous Priority AE mode managed about 10 fps, but images are cropped by a factor of 2.3x. T8 Tele-zoom mode managed -- you guessed it -- 8 fps, but images are cropped by 1.5x, similar to APS-C format. We tested these in AF-S autofocus mode, so focus was locked at the first frame. When AF-A, C or D modes are used, focus (and exposure) are adjusted during the burst, but aperture is fixed at f/3.5 or the maximum aperture of the lens, whichever is smaller. RAW files are supported in T8 mode, but not in T10.

Buffer depths are reasonable for the size of files, ranging from 13 to 18 full-resolution frames per burst before slowing down in our tests, though some (much) more expensive models have deeper buffers. You should be able to do better with typical subjects when shooting JPEGs, as our target for this test is designed to be difficult to compress. Also be aware that the A99's Extra Fine JPEGs are quite large, and buffer depths should improve when shooting Fine quality JPEGs. In Tele-zoom continuous modes, buffer depth increased to 23 frames.

Buffer clearing times are right in line with most pro SLRs, although very top-end competitors (some twice as expensive) clear buffers two to three times as deep in the same amount of time. With a very fast 95MB/s SanDisk Extreme Pro UHS-I compliant SDHC card, buffer clearing took 8 seconds after a maximum-length Large/XFine JPEG burst, 7 seconds after a RAW burst, and 9 seconds after RAW+L/F JPEG burst. Tele-zoom modes cleared faster, at 5 to 6 seconds after 23-frame bursts.

It goes without saying that faster cards usually improve buffer clearing times, but we found that the Sony A99's buffer depth was also significantly affected by card speed. Our pro reviewer was very frustrated when shooting with what we believe was a 30 MB/s SD card, experiencing buffer depths of just 13 shots and clearing times as long as 18-20 seconds when shooting in RAW mode, compared to the 18 shots and 7 seconds with the 95 MB/s card we used in the lab. Bottom line: Make sure you buy a couple of big SD cards rated 95 MB/s for use with your Sony A99, if you want to get the most from it.

Download Speed
Windows Computer, USB 2.0	14,158 KBytes/sec	Typical Values: Less than 600=USB 1.1; 600-769=USB 2.0 Low; Above 770=USB 2.0 High

Download speeds are very fast, quick enough that you won't feel the need for a separate card reader, even with large memory cards. (Note that this test was performed with a SanDisk Extreme Pro 95 MB/sec UHS-I SDHC card: Slower cards would likely show slower transfer times.)

Bottom line, the Sony Alpha SLT-A99's autofocus speed and shutter lag are excellent, cropped-mode burst speeds are very fast, and full-resolution burst performance is good for its class. Perhaps unsurprisingly, both burst speeds and buffer depths don't match up to those of professional models costing twice as much as the A99.

Battery Life
Well below average battery life compared to pro DSLRs using optical viewfinders, however Sony offers an optional battery grip which can triple battery life.

Operating Mode	Number of Shots
Electronic Viewfinder, (CIPA standard)	410
Live View LCD, (CIPA standard)	500

The Sony A99 uses a custom rechargeable NP-FM500H lithium-ion battery for power, and ships with a charger. Battery life is well below average compared to professional DSLRs using optical viewfinders, but reasonable for one equipped with an electronic viewfinder. Using the LCD monitor instead of the OLED EVF saves a bit of power, but we strongly recommend you pick up at least one spare battery for extended outings or shooting video.

Sony does however offer an optional VCG-C99AM vertical grip that can house up to two NP-FM500H battery packs in addition to a battery in the body, tripling battery life. With three batteries, the Sony A99's battery life is more in line with professional DSLRs, while offering greater flexibility in size and weight than larger pro bodies.

The table above shows the number of shots the camera is capable of (on either a fresh set of disposable batteries or a fully-charged rechargeable battery as appropriate), based on CIPA battery-life and/or manufacturer standard test conditions.

(Interested readers can find an English translation of the CIPA DC-002 standards document here. (180K PDF document))