The interchangeable mechanism itself works well. The lens-sensor unit is released with a large accessible switch on the side of the handgrip, and slides in and out sideways. The mounting rails are metal, and the unit slides into place with a satisfyingly solid click. Electrical connection to the camera body is via a wide multi-contact edge connector, and I can't help but feel that this is a potential weak spot of the design. Electrical contacts, and especially edge connectors, do wear over time, and are also vulnerable to dirt and dust. However I experienced no problems with this while I was testing the camera.
There are currently three GXR lens/sensor units available. The A12 50mm f/2.5 macro unit has a resolution of 12.3 megapixels on a CMOS APS-C sensor, and offers a maximum still image size of 4288 x 2848 pixels, and maximum video resolution of 1280 x 720 at 24fps. The S10 24-70mm f/2.5 – 4.4 standard zoom has a 10.0 megapixel 1/1.7-inch sensor, with a maximum still image size of 3648 x 2736 but only 640 x 480 video resolution at 30fps. The new P10 28-300mm f/3.5-5.6 unit seen here has a 10.0 megapixel sensor, but only of the tiny 1/2.3-inch size, with a maximum still image size of 3648 x 2736 pixels, and maximum video resolution of 1280 x 720 at 30fps.
The list prices of these units illustrate the main stumbling block of the GXR design. The P10 unit costs around £270, the S10 is £300, while the A12 with its big sensor is around £500, roughly the kit price of a Sony NEX-5 with an 18-55mm lens. Add to this the price of the body unit, currently listed at around £350 and you really have to wonder who is going to buy the GXR system when there are better specified compact system cameras available for much less.
Considering its very high asking price the GXR is lacking in several key areas. It has no mechanical image stabilisation in either the body or the current lens units, and the degree of photographic control is also more limited than I would have expected. Shooting modes include program auto, full manual and both shutter and aperture priority, as well as a limited range of scene modes. Shutter speeds from 30 seconds to 1/2000th of a second are available, but for the P10 lens unit at least only minimum or maximum aperture can be selected, hardly the sort of versatile control likely to lure users away from a digital SLR system.
The usual array of metering modes – multi-zone, centre-weighted and spot – are available, and it has a range of autofocus modes including multi-point, spot AF, multi-target AF, infinity, manual focus and a a snap-focus mode with a selection of pre-set distances. Colour and tone control at least do offer some versatility, with a range of pre-sets as well as two user-configurable settings that can be customised for saturation, sharpness and contrast as well as individual colour balance settings.