Sony Alpha DSLR-A550 Performance, Timings, and Image Quality

PERFORMANCE
All of you who skipped directly here from the Help Guide section to find out the first feature to disable should be ashamed. But since you're here... during the shoot for the first impressions story on the A550, nothing much jumped out as being of concern. Once I started wandering about doing more extensive shooting for the main article the A550 started behaving oddly.

I had the camera set for continuous AF, which should take place as long as the shutter is held at half-push. The problem was I could feel and hear the A550 doing its AF thing as I walked along with my finger nowhere near the shutter button. Setting the camera to auto and single-shot AF didn't fix things, nor did trying every shooting mode available. The camera was doing AF all by itself, and I'm thinking maybe I've got a faulty camera. After spending about an hour going over the instruction manual (when all else fails, read the manual!) it turns out the A550 was operating perfectly.

"Eye start AF" is an A550 feature enabled by default that causes the subject located in the viewfinder AF area to come into focus automatically as you look into the viewfinder. I wasn't looking into the viewfinder all the times the camera did the AF routine, but I was walking along carrying the camera in my shooting hand and as my arm would swing as I walked, the camera interpreted the proximity to my leg as the camera being looked into and activated the AF.

It's actually a pretty neat feature, but depending on how you carry your camera it does have the potential to drain the battery sooner due to performing AF unnecessarily. Personally, it would be the first thing I'd disable.
While the A550 can carry both Memory Stick and SD memory media, the type it use is designated by flipping a switch in the memory card compartment. I'd liked to have seen Sony set up the camera to automatically move on to the other media when one got full, rather than require the user to go into the compartment and switch the camera over.

While I'm not a big fan of live view, the A550 has the best system I've come across so far. The quick auto focus live view mode makes use of a separate imager that dramatically cuts AF time - and in fact you can shoot at speeds approaching 4fps in this live view mode! The A550 makes it easy to transition to either quick AF or the manual focus mode live view, but one drawback with going to manual is you'll be trying to focus by working against the focus motor in the camera unless you take the time to switch both the lens and the camera from AF to MF. Without the switch, manual focus is stiff and imprecise at best.

Shooting Performance
As one would expect from a DSLR, the A550 starts promptly - sensor cleaning is performed on shutdown by default - and acquires focus and shoots on a par with other competitors in the class. We measured shutter lag at 0.01 seconds and press-to-capture with no pre-focus at 0.20 seconds.

Shutter Lag (press-to-capture, pre-focused)

AF Acquisition (press-to-capture, no pre-focus)

Continuous Shooting

Continuous shooting rates are up to 5 fps in high speed mode, and up to 7 fps in speed priority mode. Our studio tests actually got 7.6 fps in speed priority, much better than advertised. The A550 generates that high fps rate in speed priority by establishing exposure and focus for the first shot of any sequence and applying those values to all subsequent shots. The 5 fps rate is made with exposure and focus calculated for each shot.

AF with the A550 was generally quite accurate in good conditions with the spot AF mode set - the wider area AF modes would sometimes hunt a bit before settling down on the AF point, which wasn't necessarily the point intended. There is an AF assist lamp with a range at 200 ISO of up to about 14 feet - it doesn't operate when the camera is set to continuous AF or in Auto AF when the subject is moving.

The A550 flash is listed as having a guide number (GN) of 12 (meters) at 100 ISO, even though the nominal ISO sensitivity for the camera is 200. Flash range at f/5.6 is in the vicinity of about 9 feet, so if you plan to do a lot of shooting with flash at greater distances an external flash would be a good idea - the A550 is equipped with an accessory shoe that can accept a wireless flash. Flash recycle times are given as 4 seconds by Sony, but in practice our flash recycled a bit quicker than that in moderate lighting with a high battery level.

Sony's "SteadyShot" image stabilization system is on by default in the A550, and is of the sensor-shift type. The camera will display a "camera shake" warning on the OVF or monitor if it senses the shooting conditions are beyond the system's ability to stabilize the image. There is also a "camera shake status" indicator to display the relative degree of shake at any particular time - Sony recommends shooting when this indicator is low. Stabilization should be disabled if the camera is mounted on a tripod.

Sony rates the battery in the A550 for approximately 1000 images using the OVF and about half that in live view, according to a CIPA standard that has proven reliable in my experience. The camera displays both a battery "fuel gauge" icon and battery life remaining as a percentage in the upper right of the graphic display on the monitor.

Battery charging is a little convoluted with the A550 - a steady green light on the charger means charging is underway. When the light goes out the battery has a "normal" charge, but it takes another hour after the light goes out for the battery to be "fully" charged. My vote would be Sony have the charger display a flashing green for charging, steady green for the "normal" charge and lights out with the "full" charge.

Lens Performance
The Sony f3.5-5.6/18-55 SAM zoom lens is fairly typical for kit lenses offered on this class of camera. There was some barrel distortion present at the wide end of the zoom, but pincushion was largely absent at the telephoto end. A bit of softness and a tiny amount of vignetting in the corners at wide angle was again balanced by a fairly even performance across the frame at telephoto. Chromic aberration (purple fringing) was present in some high contrast boundary areas, but the defect was virtually impossible to detect at 100% enlargement on our sample shots.

Image Quality
When I first shot the A550 and examined the default results at 100% enlargement I had the feeling the images looked just a bit too soft for my taste. I still feel that way, but upon further consideration I can also see where a lot of folks would have no problem with the images as they come right out of the camera, particularly if they never get involved with large prints. At large magnifications I think the A550 needs additional sharpening above the default values to maximize the image quality, but at the smaller end of the spectrum it can be hard to tell a default shot from one sharpened to my liking. Here's a pelican image captured at default settings, and the same image post-processed with added sharpening. If you have a hard time telling the sharpened shot from the default at the small size you're not alone - I can't either.

Default

Sharp

At any rate, the A550 has contrast, saturation, and sharpening adjustments available in the creative style palette that should be more than adequate to produce results out of the camera to please just about anybody. Here's a shot of Bandit with both contrast and sharpness set to the maximum, which seems to be more than enough.

The downside to this is the settings are available in the manual and semi-automatic modes - folks shooting full auto or the scene modes will have to post process if images produced in these modes don't meet their expectations.

Aside from sharpness, default images out of the A550 were generally accurate with regard to color fidelity.
The A550 is equipped with a "smart teleconverter" offering 1.4 and 2X multiplication factors - the feature downsizes image resolution by making use of smaller portions of the sensor to obtain the magnification factor. Here are shots at 55mm, and with the 1.4 and 2X converters enabled.

55mm

1.4X Teleconverter

2.0 Teleconverter

File sizes are drastically reduced, but the extra magnification can extend the reach of that kit lens just a bit further.

The A550 offers multi-segment, center-weighted and spot metering exposure options, with multi-segment being the default. This method worked well in most situations, but could lose some highlights in high contrast conditions. The creative style color options give the user six color options: standard (the default), vivid, portrait, landscape, sunset and B/W. Here are examples of each.

Standard	Vivid
Portrait	Landscape
Sunset	Black and White

One of the major features of the A550 is the existence of two distinct methods for managing dynamic range in image captures. The first is the dynamic range optimizer (DRO), which has automatic and five user established levels of brightness correction available. Here are shots with the DRO off, in auto mode, and at level 3 and 5. In practice, reviewing histograms indicated that the auto mode produced a level of brightness that seemed to fall between levels 1 and 2 of the user established settings.

DRO Off	DRO Auto
DRO 3	DRO 5

The second method is auto high dynamic range, which captures two quick images emphasizing highlight detail on one and shadow detail on the other, then merging the two captures into a single image. The level of exposure can be calculated automatically or set by the user within a range of 1 to 3 EV in .5 EV increments. This method is recommended for still subjects only and requires shooting discipline to remain still while the camera takes two captures. Here are examples of HDR auto, and levels 1, 2 and 3.

HDR Auto	HDR +1
HDR +2	HDR +3

Auto white balance worked fairly well with a multitude of light sources, but shot warm under incandescent in the studio and a bit cool under some very dark cloudy conditions. Lighter cloudy days were OK. In addition to auto the camera offers daylight, shade, cloudy, incandescent, fluorescent, flash and temperature settings; all but the temperature option have varying degrees of adjustment possible, while temperature can be set from 2500 to 9900 degrees Kelvin (K) in 100 degree increments.

Auto White Balance, 3200k incandescent light

With some of Sony's newest technological hardware onboard I was hopeful the A550 might provide some outstanding noise performance. The A550 does a decent job and is competitive in the class, but to my eye it didn't beat the competition and might be a tiny bit behind at least two of the other brands in the class as ISOs push out to 800 and above.

ISO 200	ISO 200, 100% crop
ISO 400	ISO 400, 100% crop
ISO 800	ISO 800, 100% crop
ISO 1600	ISO 1600, 100% crop
ISO 3200	ISO 3200, 100% crop
ISO 6400	ISO 6400, 100% crop
ISO 12800	ISO 12800, 100% crop

ISO 200 and 400 are both quite clean and hard to tell apart, with some slight noise appearing at 800 and increasing a bit at 1600. Nonetheless, the A550 is pretty good through 1600 with things starting to degrade faster at 3200 and up. ISO 6400 and 12800 are there if you need them, but those levels are for cases where nothing else will work.

Additional Sample Images
With the exception of the hummingbird shot, all of the miscellaneous images were posted as they came out of the camera. The hummingbird, originally shot at default settings, was post processed for sharpness only.