Sony DSLR-A550 Performance

Very good speed overall for a consumer digital SLR.

Startup time is about average for an SLR, but shutdown is a little slow (probably due to sensor cleaning). Buffer clearing times are a bit slow, but not surprising considering the relatively deep buffers and large files.

Mode switching is pretty fast for a consumer SLR.

Looking at the Sony A550's ability to determine that it's properly focused when shooting the same target multiple times, its speed is faster than average for a consumer model. The A550 required about 0.184 second for full AF using the center focus point. This increased slightly to 0.194 second in wide-area AF mode. Enabling the flash raised the lag to 0.219 second, but that's still pretty fast. Continuous autofocus mode lag time was 0.199 second and manual focus was only slightly faster at about 0.178 second. When prefocused, shutter lag dropped to 0.074 second, which is quite fast.

The nice thing about Sony's "Quick AF" Live View implementation is that shutter lag in Live View mode is just as fast as when using the optical viewfinder (we measured 0.188 second for single-area full AF lag). This is because the second image sensor located in the A550's viewfinder housing alleviates the need for the additional mirror flips required by most other phase-detect Live View implementations. Other phase-detect systems need to drop the mirror, focus, and raise it again to before taking a shot in Live View mode, or employ a slower contrast-detect autofocus method using the main image sensor. Since the image sensor feeding the A550's live preview is located above the mirror, the mirror stays down until the final exposure, exactly as it does in optical viewfinder mode. As noted elsewhere, though, the downside of this type of Live View implementation is lower accuracy for the Quick AF Live View viewfinder display.

To minimize the effect of different lens' focusing speed, we test AF-active shutter lag with the lens already set to the correct focal distance. We also use the same Sigma 70mm f/2.8 macro with every camera (on all platforms except Four Thirds/Micro Four Thirds and Nikon consumer models lacking an in-body focus motor), to further reduce variation, and because our tests showed that focus-determination time with this lens was close to the fastest, across multiple camera bodies from different manufacturers. Being an older design with a non-ultrasonic motor, it wouldn't be the fastest at slewing from one focus setting to another, but that's exactly the reason we measure focus determination speed, which is primarily a function of the camera body, vs focus adjustment speed, which is primarily a function of the lens.

Shot-to-shot cycle times were good for an SLR, at 0.41 second per frame for large/fine JPEGs or RAW files, and 0.40 second for RAW + JPEG frames. Continuous mode speeds are also quite good for a consumer SLR (especially given the large files), at about 4.8 frames-per-second for any quality. Speed Priority mode is exceptionally fast for a consumer model, at 6.7 frames per second, though autofocus and exposure is locked at the first frame of a burst. A Continuous Low mode limits burst speed to about 3 frames per second.

Buffer depths are pretty good for a consumer model, with 22 frames for JPEG frames with a fast card, 14 RAW frames and 7 RAW + JPEG frames. Buffer depths are generally a bit lower in Speed Priority mode, at 15 large/fine JPEGs, 13 RAW and 7 RAW + JPEG frames. In Continuous Low mode, buffer depths increase to 36, 17 and 8 frames respectively. The flash takes 3.5 seconds to recharge after a full-power shot, which is good.

Connected to a computer or printer with USB 2.0, download speeds are very fast; definitely fast enough that you will likely not feel the need for a card reader.

Bottom line, the Sony Alpha 550 is faster than the average consumer SLR in most respects. Startup time is good, mode switching is good, autofocus is faster than average, cycle time is good, and burst mode is very good, especially in Speed Priority mode. Only shut-down and buffer clearing times are slower than average.

Battery
Excellent battery life for a lithium-ion powered SLR.

The Sony Alpha 550 uses a custom rechargeable lithium-ion battery for power, and ships with a charger. Battery life is a well above average when using the optical viewfinder, and quite good in Live View mode. Still, we recommend you pick up a spare battery and keep it freshly charged and on-hand for extended outings.

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))

Storage
The Sony Alpha A550 accepts SD/SDHC or Memory Stick Pro Duo memory cards, and no card is included with the camera.

We strongly recommend buying either a large capacity SDHC, or a large capacity Memory Stick Pro Duo card, at least a 2GB card, preferably a 4-8GB one, to give yourself extra space for extended outings. (Check the shopping link above, cards are really cheap these days, so no reason to skimp.)