Sony A77 Optics

Sony A77 Optics

The Sony A77 features a bayonet lens mount, which accommodates a range of Sony and Konica Minolta lenses. The Sony A77 optionally comes bundled with a Sony DT 16-50mm F2.8 SSM standard zoom lens, which our sister site SLRGear.com felt to be a capable walk-around zoom. The lens features a built-in focus motor for fast, quiet autofocus, and is designed to be used with subframe Sony SLRs. For detailed test results, see our review of this lens on SLRgear.com.

A small button on the front of the camera releases the lens from its mount, so it can be turned and removed. The A77's CMOS image sensor is smaller than a frame of 35mm film, so the angle of view at any given focal length will not be the same as on a 35mm camera. To find the approximate 35mm equivalent focal length, multiply the focal length of the lens by 1.5. (Thus, a 16-50mm lens will provide about the same view as a 24-75mm lens on a 35mm camera.)

The Sony A77 provides both manual and automatic focus control modes, set by the Focus Mode dial on the left side of the camera's front panel, unless the lens itself has a Focus Mode switch. If there's a duplicate switch on the lens, then both must be set to allow autofocus; that is to say that if either control is set to manual focus, then the setting of the other control will be ignored. The dial on the body provides more control than that on the lens, however. Instead of simply enabling or disabling autofocus, it's also used to set the AF mode to either Single-shot AF, Automatic AF, or Continuous AF. Single-shot sets focus with each half-press of the Shutter button, while Continuous mode is constantly adjusting the focus, whether the Shutter button is pressed or not. The Automatic setting will lock focus on a still subject or continually adjust focus on a moving subject, for as long as the Shutter button is halfway pressed.

The Function button provides access to Autofocus Area options, of which there are four choices: Wide, Zone, Spot, and Local. The default option is a 19-point Wide Focus area, with AF point locations indicated by small squares visible through the electronic viewfinder or on the rear-panel LCD display. Note that of the 19 AF points, only eleven utilize a cross-type sensor sensitive to detail in both the horizontal and vertical axis, with the other eight line-type sensors being sensitive to detail in one direction only. Wide AF bases its focus on the most prominent subject detail in the portion of the image that falls within the AF brackets, and the A77 can indicate which individual AF points achieved a focus lock by highlighting those points in green on either the electronic viewfinder or LCD while the shutter button is half-pressed.

In Zone mode, the AF points are addressed in one of three groups: either a group of seven points in a column near the horizontal center of the frame, or one of two clusters of six points in the left or right of the frame. The camera will still automatically choose one or more points at which to achieve a focus lock, but it will restrict itself solely to point in your chosen group while doing so. In Spot mode, the A77 uses only the centermost AF point, and only this point is indicated by a square target box in the center of the viewfinder or live view display. Finally, Local mode is Sony's terminology for a manual AF area selection, also known as Flexible Spot in some earlier models. This lets you manually set the main AF point by using the Multi-controller to highlight one of the 19 available AF points. The active AF area is given a bolder line in the viewfinder and live view displays, and is again highlighted in green upon focus lock as a visual reminder of which point was manually selected.

A couple of the more unusual features of the Sony A77 are its Face Detection and Smile Shutter functions. Face Detection can detect up to eight faces simultaneously within the image frame, and adjusts focus, exposure, image processing, and flash output. Detected faces are indicated with gray frames, which turn white when they fall under an autofocus point. When focus lock is achieved, the camera indicates which faces it feels were correctly focused with a green frame. When no faces fell under a phase detection sensor, the A77 reverts back to showing the AF points that achieved a lock, instead. Optionally, you can program the camera to recognize the faces of up to eight specific individuals, who will then be prioritized over other faces whenever they're recognized in the image frame. Smile Shutter, meanwhile, can be used to trip the shutter automatically when a smile is detected. You can adjust the "sensitivity" of Smile Shutter to either "Slight", "Normal", or "Big" smile, and a gauge at the left of the screen shows the degree of smile that the A77 is currently detecting, along with a mark indicating the point at which the shutter would be triggered.

A depth-of-field preview button can be found adjacent to the grip, at the base of the lens mount. When held in, the A77 stops down its aperture to the selected value, allowing preview of the depth of field available in the scene. The function is rather more useful than in the typical SLR, however, in that while the view through the electronic viewfinder will dim while the aperture is stopped down beyond the camera's ability to correct for, the camera otherwise adjusts preview sensitivity to attempt to show the image with correct brightness. This makes it quite a bit easier to gauge depth of field with small apertures in good light (but perhaps makes the preview image grainier in low light conditions).

Sony A77 AF Assist

The Sony A77 has a dedicated AF assist lamp, based around a bright red LED that projects a vertical line pattern, providing some high-contrast edges for easier and more accurate focusing on nearby subjects in dim lighting. This has two advantages over the more common flash-based AF assist on cheaper SLRs: it functions regardless of whether your flash strobe is raised, and doesn't dazzle your subject quite as much, so it's less likely to cause a blink.

Sony A77 Anti-Shake

The Sony A77 also employs Sony's SteadyShot Inside anti-shake technology, which uses a highly sensitive accelerometer, and a moveable platter on which the CMOS sensor assembly is mounted. Together, these allow the A77 to counteract camera movement with movements of the image sensor, rather than the more common approach of moving an optical element inside the lens.

Depending upon shooting conditions and the lens type attached, Sony claims that the SteadyShot Inside anti-shake system in the A77 provides anywhere from a 2.5 to 4.5-stop reduction in the blurring produced by camera shake. Translating that into real-world shutter speeds, a two-stop improvement means that a shutter speed of 1/30 second would give you the same resistance to blur from camera shake that a speed of 1/120 would without anti-shake. A 4-stop improvement would mean you could shoot as slow as 1/6 second and get the same results (blur-wise) as when shooting at 1/120 second unaided. Even the lower end of the specified range of effectiveness means a pretty significant improvement in one's ability to hand-hold long exposures.

Sony A77 Anti-Dust Technology

To help combat dust particles on the CMOS sensor from changing lenses, Sony has included both an anti-static coating on the low-pass filter and uses the sensor shift mechanism to automatically shake dust free each time the camera is shut off. There is also a manual cleaning mode, where the camera triggers a longer burst of sensor shift shaking. We've generally found dust-removal systems based on cameras' anti-shake systems less effective than those that use an vibrate the sensor ultrasonically, but it bears noting that no dust removal system completely eliminates the need for occasional manual sensor cleaning.

Sony A77 Optical Test Results

Below are the results of our optical tests of the Alpha A77 with the Sony DT 16-50mm f/2.8 SSM kit lens. The test images shown on most other pages of this review were taken with very sharp references lenses, so we use this page to explore kit lens quality.

The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Sony Alpha SLT-A77 Photo Gallery .