Sony A77 Flash
The Sony A77 features a built-in, pop-up flash, which operates in either Auto, Fill-Flash, Slow-sync, Rear Sync, Wireless, and Flash-off modes. To release the flash from its compartment, press the button on the left side of the EVF housing. The release mechanism is electronic, so bumping the button when the camera is switched off won't cause the flash to pop open and get damaged in your camera bag. Close it again by pushing the flash head back down.
The main Flash modes are changed from the Function menu. In Auto flash mode (available only in the camera's Auto, Auto+, or some Scene Selection modes), the camera automatically determines when to fire the flash based on lighting conditions, and will pop-up the flash automatically. In Fill-Flash mode, the flash fires with every exposure, regardless of ambient lighting. The Rear Flash Sync mode fires the flash at the end of the shutter time, rather than the beginning. If you have moving objects in the scene with lights, such as a car, this will produce a sharp image of your subject, with a "motion trail" following behind it when shooting at slower shutter speeds. We'll come to Wireless mode in a minute. One mode isn't accessed from the Function menu, but rather, via a dedicated control: the AEL button doubles as a Slow-sync button, which sets the flash to fire for foreground fill exposure, while allowing the background to "burn in". (If the AEL button is configured to a different function, Slow-sync can be assigned to the ISO or AF/MF buttons.) The flash is off when Flash Off mode is selected, or when the flash is down in non Auto exposure mode.
A Flash control option in Record Menu 2 allows you to select between ADI flash, Pre-flash TTL, and Manual flash. The only difference between the first two is that ADI takes into account focus distance information from the lens, which can make for more accurate flash exposures -- especially with highly reflective subjects. A Red-Eye Reduction option is available through Custom Menu 1. When Red-Eye reduction is enabled, the camera will fire a few low-power flash pulses before it actually snaps the picture, to make the pupils of your subjects' eyes contract.
Flash exposure compensation can be set via the Function menu, within a range of +/- 3 stops, in 1/3-stop increments. This is in addition to standard exposure compensation.
The A77's built-in flash has a Guide Number (GN) of 12 meters or 39.4 feet at ISO 100, about typical for a consumer SLR. Maximum sync speed is a useful 1/250s. High Speed Sync (HSS) shooting with shutter speeds up to 1/4000s is available with Sony HVL-F58AM and HVL-F43AM external flash units.
The A77 also has a top-mounted hot shoe for attaching an external flash unit. The shoe design and contact arrangement are proprietary, set up for Sony's own dedicated flash units. Neatly hidden under a rubber flap on the left side of the body is a PC-sync terminal, for attaching to studio strobes.
The Wireless mode lets the Sony A77 work with compatible remote flash units with wireless capability, specifically the Sony HVL-F58AM and HVL-F43AM. Four separate control channels are available for wireless operation, to allow multiple photographers to work wirelessly in the same area without interfering with each other, and flashes can be addressed in three separate groups. Operating in Wireless mode with a compatible external flash unit, the Sony A77's flash exposure compensation adjustment can adjust the intensity of the external flash remotely, once the camera and flash unit have been initially synced to each other.
Flash Test Results
Coverage and Range
A powerful flash with somewhat narrow, uneven coverage at wide-angle.
Coverage. Flash coverage was quite uneven at wide-angle (16mm), leaving very dark corners in our flash coverage test image, though 16mm (24mm equivalent) is wider than most kits lenses. Some of the fall-off is also due to the lens itself, though the majority is from the flash. Illumination isn't terribly even vertically either, with some darker horizontal bands. Coverage was much more uniform at telephoto (50mm), though much of the image has a slightly reddish tent.
Exposure. Our Indoor Portrait test scene was bright with only +0.3 EV flash exposure compensation at ISO 100, which is less than the average compensation needed for this scene (+0.7 EV). The camera's Slow-Sync flash mode produced a very bright image at the default setting, though with a stronger orange cast from the room lighting from the longer exposure.
ISO 100 Range. With the 16-50mm kit lens at maximum aperture, flash exposures started out bright at 6 feet, peaked at 11 feet, and remained bright all the way to the limit of our test at 16 feet. Very good range, though the fast f/2.8 kit lens helped here.
Manufacturer Specified Flash Test. The Sony A77's built in flash is rated with a Guide Number of 12m at ISO 100, which works out to 14 feet at f/2.8. In the shot above, the A77 performs as Sony says it will, producing a bright exposure at the rated distance with its ISO set to 100. Our standard test method for flash range uses a fixed setting of ISO 100, to provide a fair basis of comparison between cameras. We've now also begun shooting two shots using the manufacturer-specified camera settings, at the range the company claims for the camera, to assess the validity of the