Sony Alpha a700 review
Firstly we need to talk about that sensor. The original IMXO21 code name has been changed to the more market-friendly 'Exmor', and the chip contains 13.05 million pixels, giving an effective count of 12.2MP. The APS-C-sized sensor offers a revolutionary on-chip A/D conversion system, which works to reduce noise in a different way from most sensors.
Usually the signal from the sensor moves down an electronic pipeline to the processor, which introduces noise as the signal leaks on the journey. The processor performs the Analogue/Digital conversion (A/D), including signal amplification to raise the ISO: if necessary – another noise introduction – and performs the appropriate image processing such as white balance, sharpness, colour, etc.
The Exmor’s built-in circuitry performs the analogue noise reduction before the A/D conversion, then performs digital noise reduction, and further noise reduction is performed inside the Bionz processor. The result is, according to Sony, better noise control even at high ISO:. On top of all that, more noise reduction is applied at sensitivities from ISO: 1600. Incidentally the camera’s top sensitivity is ISO: 3200 with a boost option up to ISO: 6400.
The initial announcement made claims that the sensor can record at 10.39fps, however the A700 manages only 5fps to the capacity of the card in normal JPEG mode. Still, it offers us a glimpse of the future, and not just from Sony, as it may well sell this chip to other manufacturers as it has in the past.
Konica Minolta’s pioneering of sensor-based image stabilisation is continued under the Sony umbrella using the Super SteadyShot feature, which the company claims is improved further on the A700. Sony now states the user can shoot at between 2.5 and four stops slower shutter speeds than on a non-IS camera, so at 200mm for example, instead of shooting at 1/250sec, you could hold the camera at 1/15sec to 1/45sec and still maintain sharpness.
Built into the image stabilisation is a dust-protection system, whereby the sensor vibrates at high speed to dislodge any dust. Unlike other systems, this system kicks in when the camera is turned off, so enabling a faster start-up time. An anti-dust coating on the low pass filter to reduce static (and so reduce the chances of dust clinging to the sensor in the first place) augments the sensor vibration.
Dynamic Range Tool
Another improved feature of the Alpha is the Dynamic Range tool which expands the capacity for recording extremes of highlight and shadow. The system offers a choice of three modes – standard, auto and selectable – with a choice of five levels of enhancement.
Exposure Metering and AF
Sony has also revamped the metering, with a 40-zone honeycomb metering, along with spot- and centreweighted metering. The auto focus system is revamped, with a new centre dual-cross 11-point AF. A new AF sensor promises greater focusing accuracy at wide apertures.
Usefully the camera features a PC socket for using studio or off-camera flash, while a built-in flash offers a GN of 12m @ ISO: 100 and a hotshoe allows the use of Sony-compatible flash units. Flash sync speed is set at 1/250, dropping to 1/200sec in SteadyShot mode.
Images are saved to Compact Flash, while a secondary slot accepts MS Duo cards, and the camera has a wide choice of recording formats, including 12-bit Raw and Raw+JPEG. Sony has introduced a new format into the mix in the form of cRaw, or Compressed Raw, which reduces the size of the image file by around 30%. The buffer can hold 25 cRaw files rather than 18 in full size Raw. Sony and Adobe are co-operating to allow the new file to be supported in the next update of Adobe Camera Raw software. For now, only the included Sony software can open the files.
The software includes a tethered shooting option, giving remote control of the camera via a PC or Mac, which is useful for some studio work or for controlling the camera in tricky locations. The camera also comes with a wireless remote control, allowing shutter operation when shooting.