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Performance

The Alpha 550 offers some of the fastest continuous shooting in its class, with high speed shooting possible at up to 7 frames per second (though at that rate you lose autofocus and metering is fixed at the first exposure). Even so, the standard 5 fps continuous burst mode is pretty impressive.

Putting aside the headline-grabbing continuous shooting for a moment the Alpha 550 sits in the middle ground when it comes to overall operational speed, with the performance issues mainly centered around the rather sluggish card read/write speeds (which are pitiful when using Memory Stick, merely pedestrian with a fast SD card.

Focus speed is pretty good (if not class-leading) and - thanks to Sony's two-sensor system - the A550 is (almost) as fast in live view as it is when using the viewfinder.

Timings & File Sizes

Timing Notes: All times calculated as an average of three operations. Unless otherwise stated all timings were made on a 4672 x 3104 JPEG Fine (approx. 6,300 KB per image).

The media used for these tests was a 4 GB Sandisk Extreme III (30mb/s edition) SD card

Action
Details
Time, secs
(8 GB Sandisk)
Power Off to On   0.5
Power Off to Shot   0.5
Shot to shot time (JPEG)   0.9
Shot to shot time (RAW)   0.9
Shot to shot time *1 Live View (Standard, secondary sensor LV) 1.0
Shot to shot time *1 Live View (MF Check Live View) 1.2
Power On to Off *2   1.2

*1 Timings for raw and JPEG files are the same
*2 This is the time from when the switch is set to off until activity light goes off

Continuous Drive mode

The Alpha 550 offers three continuous shooting modes: low speed (around 3.0 fps); high speed (around 5.0 fps) and a new 'Speed Priority' mode that can fire off up to 7 frames per second. The only drawback of this ultra-fast shooting mode is that focus and exposure are fixed with the first shot, limiting its usefulness for subjects moving towards or away from you.

To test continuous mode the camera had the following settings: Manual Focus, Manual Exposure (1/500 sec, F5.6), ISO 200. Measurements were taken from audio recordings of the tests. Media used were the same as above.

The tests carried out below measured the following results for JPEG and RAW:

  • Frame rate - Initial frame rate, this was always 5.0 fps (+/- 0.2 fps) at the higher continuous shooting setting and 7.1 or 7.2 fps when using the Speed Priority mode (which only focuses the first shot).
  • Number of frames - Number of frames in a burst (for JPEG there is no limit with a fast card)
  • Buffer full rate - Frame rate if shutter release held down after burst (buffer full)
  • Write complete - How long after the last shot before the card access lamp goes out

Burst of JPEG Large/Fine images Continuous High

Timing
4 GB Sandisk Extreme III
Frame rate 4.8 fps
Number of frames unlimited
Buffer full rate n/a
Write complete ~ 2.0 secs

Burst of Raw images Continuous High

Timing
4 GB Sandisk Extreme III
Frame rate 5.0 fps
Number of frames 14
Buffer full rate 1.2 fps
Write complete ~ 10.8 sec

Burst of RAW+JPEG images Continuous High

Timing
4 GB Sandisk Extreme III
Frame rate 5.0 fps
Number of frames 7
Buffer full rate 1.1 fps
Write complete ~ 7.5 sec

Burst of JPEG Large/Fine images Continuous 'Speed Priority'

Timing
4 GB 4 GB Sandisk Extreme III
Frame rate 7.2 fps
Number of frames 17
Buffer full rate 5.5 fps *1
Write complete ~ 3.0 sec

Burst of Raw images Continuous 'Speed Priority'

Timing
4 GB 4 GB Sandisk Extreme III
Frame rate 7.1 fps
Number of frames 13
Buffer full rate 1.3 fps
Write complete ~ 10.4 sec

Burst of RAW+ JPEG Large/Fine images Continuous 'Speed Priority'

Timing
4 GB 4 GB Sandisk Extreme III
Frame rate 7.1 fps
Number of frames 7
Buffer full rate 1.1 fps
Write complete ~ 7.1 sec

In our tests the Alpha 550 delivered pretty much exactly what Sony said it does, with the only slightly disappointing aspect being the time the camera takes to write the contents of the buffer to the SD card, which will only be a concern if you really like to take a lot of long bursts of raw images.

Continuous shooting in Live View modes

In the normal live view mode (the one using the secondary sensor, activated by the LV/OVF switch) the maximum frame rate drops to 4.0 fps (high speed mode) but otherwise everything is the same as above. You can use the Speed-Priority mode with Live View activated (and get the same 7fps performance as you would with the viewfinder), but it's kind of pointless as you lose live view whilst shooting. In the main sensor 'MF CHECK LV' mode the only difference is that the first frame takes a little longer than the following frames (at which point the camera isn't in LV mode any more).

Differences with Memory Stick

In our tests (using a 2.0 GB MS PRO DUO Mark 2) performance with Memory Stick was almost identical to SD until the buffer was full, at which point the MS card's slower write speeds had a serious impact. The main differences are:

  • Write complete times are considerably higher (JPEG: ~ 10 secs, Raw: ~ 30 secs)
  • Buffer full rate when shooting raw is slower (around 0.4 frames per second)

It's worth noting that the difference between SD and MS would almost certainly be reduced by use of one of the newest faster 'HG' flavor cards (though given the lower price and ubiquity of SD cards there's little reason to use Sony's proprietary format unless you're already heavily invested).

USB transfer speed

To test the Alpha 550's USB speed we transferred approximately 380 MB of images (mixed RAW and JPEG) from a Panasonic Pro High Speed 1GB SD card. With a transfer speed of around 12 MB/s the A550 is similar to most other cameras in its class, and though not as fast as a dedicated reader, is no slouch.

Method
Transfer rate
Sony Alpha 550 USB 2.0 - Mass Storage 12.2 MB/sec
SanDisk Extreme III in USB 2.0 reader 17.0 MB/sec

Autofocus speed / accuracy

Obviously focus speed is as much about the lens as it is about the camera, but our experience with the Alpha 550 was - as it has been with most Sony SLRs - generally very positive. We were mostly using it with Sony's premium 16-105mm DT lens, the new 30mm macro and the 50mm F1.4, and were impressed by the speed and accuracy of the focus system, though it is noticeably faster when using the newest SAM lenses (the 18-55 and 50mm F1.8 are both very speedy, the macro, inevitably, less so). There was occasional hunting in low light but overall the system compares very well with similarly positioned competitors in single-shot mode.

We weren't overly impressed with the continuous autofocus, which can't keep up with the 5fps motordrive (at the highest 7fps setting it doesn't even try). Few cameras in this class are that well suited to high speed continuous shooting with autofocus, but next to, say, a recent Nikon the A550's AF tracking feels sluggish.

The Alpha 550 sees the return of the eye sensor (which allows the camera to start focusing as soon as you raise the viewfinder to your eye), and with the fast AF the camera is often ready to shoot before you've even decided to press the shutter. But where the A550's AF is really a class on its own is in live view mode, where it is significantly faster than any of its competitors thanks to the secondary live view sensor system that allows the use of conventional phase-detect AF. It's also worth mentioning that the Alpha 550 is the only camera on the market that can do face detection using Phase Detect focus (in Quick AF Live View mode).

Battery life

The Alpha 550 is powered by the NP-FM500H high capacity cell (as used in the Alpha 700, 900 etc), not the weedy mini battery found in cameras like the A380. Battery life - even using Live View Mode - is excellent: if you rarely use flash or playback mode it's possible to get well over 1000 images in viewfinder mode from a single charge.

Live View Mode
~ 480 images
Viewfinder Mode
~ 950 images

* Sony figures, measurement method based on the CIPA standard.

Image Stabilizer

The DSLR-A550 features Sony's CCD-based "SteadyShot inside" optical image stabilization which is common across their entire range of digital cameras. The A550 also features a 'shake-indicator' in the viewfinder, which shows you when, from a camera-shake point of view, it is safe to press the shutter button. Performance is broadly in line with other Alpha models.

The stabilization test

At a range of shutter speeds a total of twenty hand-held shots were taken of a static scene, ten without stabilization, ten with the activated SteadyShot system. For these tests we used the Sony 18-55mm SAM kit lens at 55 mm to produce a 82.5 mm equiv. FOV. The test chart was approximately 5 m away from the camera. We're looking for how much improvement the system offers, not an absolute measurement of 'how low you can go' with the shutter speeds.

The resulting images were then inspected and given a blur score from zero to three where zero represented a very blurred image and three a sharp image with no noticeable blur (see crop examples below). Obviously the amount of blur which is acceptable will depend on your personal taste and the final image size (for instance a '2: Soft' will still look fine as a 4x6 print or in a web gallery). Example crops from these four blur scores can be seen below.

0: Very blurred 1: Blurred
2: Soft 3: Sharp

Hand-held, no stabilization (18-55 mm kit lens, 82.5 mm equiv. FOV)

With the kit lens at its longest focal length we were able to get 100% sharp shots at anything above 1/100th second (which you'd expect) but the percentage of usable shots fell quickly after 1/30th sec.

Hand-held, with SteadyShot on (18-55 mm kit lens, 82.5 mm equiv. FOV)

With the activated SteadyShot system we get a pretty significant improvement. At 1/8 sec we still get 100% usable shots (60% sharp) and even at a shutter speed as slow as 1/2 sec 50% of all images would still be good enough for at least smaller prints. The system gives you a 2-3 EV advantage across all shutter speeds and especially at slow shutter speeds your chances of getting a sharp shot increase dramatically.

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