Sony SLT-A55 Digital Camera Review$899.99
Lens & Sensor
The SLT-A55 uses an Exmor APS CMOS filter, which measures 0.925 by 0.614 inches (25.5 by 15.6mm) and has a resolution of 16.7 megapixels. Of these, about 16.2 megapixels are used, with the rest being used for image stabilization. This CMOS chip uses RGB sensors, with the color filters being mounted onto the chip surface.
This sensor sits behind a translucent mirror, which is in a fixed position. Conventional SLRs work by moving the mirror out of the way when taking a photo, but the mirror of the A55 is translucent, so it lets most of the light through, but reflects a small amount into the viewfinder housing, where it is used to meter the scene and to focus. This means that the camera can focus and shoot images at the same time; it does not have to focus with the mirror down and then move it out of the way to take the photo.
Some users of this camera have reported a problem with this, seeing a ghost image caused by internal reflections from this mirror. We did see this on a few images (particularly those where bright objects were shot against dark backgrounds), but this was not a significant problem: the ghost image was much darker than the actual one, and were not visible in most shooting situations.
On the back of the A55 is the electronic viewfinder, which has a resolution of 1,440k pixels. Because it is electronic, it shows the image being captured by the image sensor, rather than the image through the lens that normal SLR cameras capture. We found the viewfinder to be comfortable to use, although it is a little difficult to see the entire image when wearing glasses: the edges of the image are blocked by the edge of the viewfinder unless you press your eye close to the viewfinder, which leads to smudges on the glasses. The image does break up somewhat with fast moving objects, if you pan the camera quickly or if you are shooting in very low light.
Diopter adjustment is available from a small dial on the right side of the viewfinder housing, and we found the viewfinder to be comfortable to use with spectacles. Below the viewfinder is an eye sensor, which switches from the screen to the viewfinder when it detects an approaching eye. However, it is also triggered by hands or fingers, and this is a little annoying when you are reaching around the camera body to press one of the buttons: the sensor is often triggered by the hand. This can be disabled, though, and a button on the top of the camera body can be used to switch between the viewfinder and the screen.
The LCD screen of the A55 is a large, bright 3-inch LCD with a 921k pixel resolution. This is very sharp and clear, and is visible in all but direct sunlight, which is where you would use the viewfinder instead of the screen. The screen is also articulated, with a hinge and pivot allowing you to flip the screen out and rotate it around. This allows the screen to be rotated so that it can be used for shooting with the camera held above, below or behind you. It is possible to also use this to shoot self-portraits, but the screen is somewhat obscured by the camera. Some Canon models use a side hinge, which is better suited to this, as the screen is less obscured by the camera body when it is rotated around to the side.
This rotating hinge also allows you to turn the screen around so that it can be folded flat against the camera body, protecting it from scratches and bumps. We were not able to test this to destruction, but we did find that the LCD screen and hinge feels tough: it is unlikely to break off or be otherwise damaged by anything other than extreme force.
There are two flash options with this camera: a small built-in flash, or attaching an external flash to the hot shoe on the top of the camera body. The built-in flash is a pop-up model located in the front of the viewfinder housing. It pops up when the small flash button is pressed: it does not pop up automatically. We found it to be reasonably powerful, penetrating total darkness out to a distance of about 11-12 feet, and having a pretty even flash pattern, although there is some vignetting at the edges of the frame at the widest angle setting of the kit lens: the edges of images taken there are noticeably darker than the middle. The flash sync speed is a pretty speedy 1/160 of a second: useful for capturing fast moving objects.
The other option is to attach an external flash to the camera through the hot shoe. This is a proprietary design: it will not work with standard hot she flash guns. Sony is the only company to make compatible models, and their HAL-F42AM flash costs $299.99. They do also offer a microphone that can plug into this port.
The SLT-A55 offers a small number of ports, but the important ones are on offer, with a mini HDMI port, a multi-function USB and analog A/V output and a microphone input on the left rear side of the camera body. On the left front side is a single port for attaching an external GPS receiver. The camera does have an internal GPS receiver, but an external unit may have better sensitivity or be more accurate.
The power source of the A55 is a small 1080mAh battery that fits into a cavity in the camera grip. This battery (model NP-FW50) is recharged with the included charger: it cannot be recharged in the camera body. Sony quotes a battery life of 330 images with the viewfinder and 380 when using the screen, but this feels a little optimistic: we found that the battery did not typically last for more than a day of serious shooting. A spare battery would be a sound investment, and these cost about $60.
The SLT-A55 can handle the Pro Duo and Pro-HG Duo variations of MemoryStick flash memory cards that Sony offers, but it can also work with SD, SDHC and the newer SDXC memory cards. Both types of card fit into the same slot next to the battery, below a latched cover.