The new firmware upgrade, which Sony has released today, is aimed at refining "shooting responses and creative options for the A900 and A850 digital SLRs - the firm's two full-frame cameras.

The upgrade offers a more responsive and faster autofocus, "thanks to improved AF motor control and smarter distance detection of out-of-focus objects," claims Sony.

The firm has also extended creative options by broadening the range of exposure value (EV) compensation settings, which have been increased from ±3EV to ±5EV. "Selected compensation value is displayed in the navigation display on the main LCD screen of both cameras," says Sony. "This boosted EV compensation range gives extra headroom when composing extremely high- or low-key images."

The exposure bracketing range has also been increased from a maximum of 4.0EV  - three shots at -2EV, 0EV, +2EV - to a maximum of 6.0EV - -3EV, 0EV, +3EV. "This wider range gives added flexibility when capturing multiple frames at different exposure values; for example when acquiring images for the creation of powerful post-shooting HDR effects," claims Sony.

Finally, a new menu option now allows shutter release to be enabled even when the camera body doesn't detected an attached lens. This will allow photographers to use both cameras in astrophotography - when attached to a telescope.

The firmware is available to all registered A900 and A850 owners, and can be found on the Sony website.