Sony Alpha 99 review
Image: With the Sony Alpha 99's fixed mirror there is little camera shake during capture, which benefits long exposures. This image is pin-sharp
The Alpha 99 uses a 24.3-million-pixel, Exmor CMOS sensor with a fixed translucent mirror, but it's a full-frame size, which means it has a large surface area to collect light and its photodiodes are physically large. This should result in a significantly better low-light performance than that of the Alpha 77, which has the same pixel count but uses a smaller APS-C-sized sensor.
Sony claims that the Alpha 99 has more than twice the saturation, one and a half times the sensitivity and a 50% reduction in noise in like-for-like images taken with the Alpha 900. Given that the full-frame Alpha 900 has a similar resolution but uses a more traditional DSLR mirror mechanism without 1/3EV light reduction on the sensor, we can see just how much more efficient Sony claims to have made its sensors. Factors include what the company claims is a thinner wiring layer between the on-chip lens and photodiode, allowing more light to reach each photodiode. Also, a newly developed ‘multi-segment' low-pass filter is claimed to let more light through than a conventional low-pass filter would, so we should expect sharp images, too.
A new Bionz engine produces 14-bit raw files. This processor uses the same adaptive noise reduction as Sony's Cyber-shot DSC-RX100, which works by analysing the picture detail, be it edge or texture, and then applying more noise reduction to parts of the frame where detail is not as important and less to where detail is crucial.
The Alpha 99 features sensor-shift SteadyShot for image stabilisation up to an effective 2.5-4.5EV. Having this feature in-camera means that Sony Alpha and Konica Minolta lenses do not need stabilisation built in. Also, in using a fixed mirror, the Alpha 99 is not affected by the shake caused by mirror-slap, which the Alpha 900 suffers from. There is therefore no need to include a mirror-lock drive mode.
Phase-detection AF with 102 focal points is built into the imaging sensor, working alongside the 19-point phase-detection AF sensor. Sony has introduced a new AF mode (AF-D) that uses both these systems together. I will go into more detail about this later.
There are a number of shooting modes, including an 8fps and 10fps tele-zoom high-speed burst (see High-speed Shooting). Bracketing is available for the Dynamic Range Optimizer (DRO) and white balance over three consecutive frames, while bracketing for exposure up to ±3EV is possible across up to five frames.
Image: An exposure at +3EV is around the limit for crisp detail in shadow areas
The HDR mode is available in JPEG only and records over three frames up to ±6EV, but the frames are recorded consecutively so a tripod is advised. Other modes include the sweep panorama, while the teleconverter enables a 1.4x or 2x focal-length magnification at a reduced file size. It would be nice to see multiple-exposure and time-lapse modes included, as many other high-end models feature these.