This week Olympus issued a [URL="http://dpnow.com/5798.html"]firmware update[/URL] for one of its telephoto zoom lenses, the Zuiko Digital 70-300mm. Seems pretty routine, you might think.

But actually this particular firmware update was a bit out of the ordinary.

If you aren't a follower of Four Thirds, here's a brief explanation. Some of the more recent Olympus and Panasonic interchangeable lens camera models support a live view autofocus mode that uses the image sensor itself to determine focus, instead of the more conventional phase-detect AF sensors. Phase detect sensors require the reflex mirror (if present) to be dropped down, so interrupting live view, to find focus.

Most camera manufacturers who have adopted imager-based live view, also known as contrast-detect live view, have found that their existing lenses, optimised for phase detect AF, can only change the focus in the lens very slowly in imager AF mode for live view AF. Nikon even goes so far as to call this mode 'Tripod Mode' AF.

However, Panasonic and Olympus have equipped some of their latest lenses with AF motors that are geared specially to focus quickly in either imager AF or phase detect modes.

The Zuiko Digital 70-300 was released at the end of 2007 and nobody ever thought that this lens would work in imager AF mode. But this weeks firmware upgrade has endowed it with just this capability, much to the delight of many of its owners who have Panasonic and Olympus cameras that can exploit this mode.

So the question is - why did it take almost a year and a half for Olympus to implement this firmware modification? Secondly, are we now going to see a rash of firmware updates to add the same functionality to other older lenses in the Olympus range? And what about other manufacturers? Will Nikon and Canon be adding performance in live view AF to their lenses?

Olympus does have an incentive. This summer, the company has announced that it will be launching its first Micro Four Thirds cameras. These won't have phase detect AF at all, so imager AF is the only route to autofocus and if your older Four Thirds lens won't AF in this mode, its usefulness will be seriously compromised.