When you consider the incredible flexibility offered by digital capture (unencumbered by the physical need to put the film behind the lens and to advance it frame by frame) it's perhaps surprising that the digital interchangeable lens camera has remained so firmly rooted in a basic design that hasn't changed since the 1950's. The single lens reflex does its job very well, but building a camera around a mirror box seriously ties the designer's hands - not only in the physical size and shape of the body, but in the lenses too (the distance to the sensor means retrofocus designs are needed to overcome the distance from the sensor to the flange).

The reasons for this seemingly dogmatic attachment to the single lens reflex are fairly obvious; the main players in the market have a vested interest in maintaining compatibility with legacy lenses and offering as seamless a transition from film to digital as possible for their millions of existing users. Besides, it's a lot easier to design a body that works in the same way SLRs always did than to launch an entirely new lens system.

There have also been some technological barriers to deal with; the lack of digital displays good enough to produce an electronic viewfinder that can even get close to a good mirror and prism, and the fact that current phase-detect autofocus systems won't work without a mirror being the two most commonly cited.

It is perhaps unsurprising then, that the first company to challenge the SLR hegemony is Panasonic, a manufacturer with no legacy film SLR system to support and a share of the digital SLR market so small that it's relatively easy to simply drop it and move on. We strongly suspect that the L10 will be the end of Panasonic's brief foray into the standard Four Thirds System and that - for all the joint development statements - it was Panasonic, not Olympus that was the driving force behind the introduction of Micro Four Thirds.

And so we have a new system with a new lens mount and this, the G1; the world's first electronic viewfinder interchangeable lens camera. From the outside it looks for all the world like a conventional SLR (albeit a very small one) - we're told that the design (complete with faux prism 'hump') is deliberately conservative; Panasonic's research has shown that its target market (particularly in Japan) still prefers a camera that looks like a camera is supposed to, and wasn't going to risk falling at the first hurdle by producing something too radical.

On the inside of course it is indeed radically different to every SLR on the market; the mirror and pentaprism/pentamirror viewfinder is gone, replaced by a live view-only system using either the newly-developed high resolution electronic viewfinder or the large articulated rear screen (which, interestingly, has a 3:2 aspect ratio - not the 4:3 ratio of the sensor).

Panasonic's stated reasons for introducing Micro Four Thirds are simple; to produce smaller cameras that act more like compact DSCs whilst offering the quality and versatility of a DSLR - and in doing so to convert some of the millions of compact camera buyers who - according to research - are put off digital SLRs by the bulk, complexity and lack of user-friendliness. And our initial tests would suggest that they have solved at least one of the technological problems mentioned earlier (the contrast-detect autofocus is easily as fast as any other entry-level DSLR). The viewfinder is also very impressive and significantly better than any viewfinder we've seen on a digital stills camera before.

The Micro Four Thirds standard - and the Panasonic G1 - represents the first complete break with legacy SLR technology going back well over half a century, and as such represents an important moment in digital photography's short history. It would be fair to describe it as the first truly 'all digital' interchangeable lens camera, and I think it would also be fair to say it finally delivers on the promise made for the Four Thirds system when it was first introduced back in 2002 (to quote from the original press release 'The major benefit of Four Thirds System is that it will allow the design of dedicated, high-performance digital camera lens systems that are more compact than their 35 mm film SLR camera lens counterparts').

It's worth remembering that this 'mini SLR' thing has been tried before; in the mid to late 1990's Canon, Nikon and Minolta all launched compact SLR systems based around the new APS film format, and all failed to make any impact at all. Of course a lot of that was down to timing (digital was already starting to reshape the entire landscape of the photo industry), but crucially these systems also offered little beyond a size reduction (and a far more limited choice of films) to differentiate them from their 35mm counterparts.

Where the G1 - and Micro Four Thirds - has the edge is that there has never been a wider gap between the image quality offered by compact cameras and SLRs. By offering a camera that works and handles like a compact (Panasonic FZ users will feel right at home) but produces output a lot more like an SLR, Micro Four Thirds has carved out a potentially lucrative niche for itself in a market crying out for innovation. It may seem like a relatively low-key product to herald a minor revolution in the digital SLR market, but have no doubt, the G1 is one of the most interesting products we've had under this roof for quite some time. Let's see how it performs in our in-depth review.

Micro Four Thirds

Olympus and Panasonic announced the new, mirrorless format / lens mount based on (and compatible with) Four Thirds in August 2008. The Micro Four Thirds system uses the same sensor size (18 x 13.5 mm) but allows slimmer cameras by removing the mirror box and optical viewfinder. The new format has three key technical differences: (1) roughly half the flange back distance (distance from mount to the sensor), (2) a smaller diameter lens mount (6 mm smaller) and (3) two additional contact points for lens-to-body communication (now 11 points). Removing the mirror mechanism allows this shorter flange back distance, meaning lenses for the new mount can be considerably smaller than current Four Thirds designs. The format will require framing to be carried out using Live View on either the LCD monitor or an EVF. Existing Four Thirds lenses can be used on Micro Four Thirds cameras using an adapter.

Lens compatibility

Micro Four Thirds is an extension of the Four Thirds standard that Olympus, Leica and Panasonic have used for their recent DSLRs. An adaptor ring is available, allowing existing Four Thirds lenses to be mounted. Auto Focus only functions on lenses compatible with contrast-detect AF, which limits choice. Click here for an up-to-date list of compatible lenses on the Panasonic website.

The DMW-MA1APP adapter allows existing Four Thirds lenses to be used with the Micro Four Thirds mount. The adapter is not designed to work with other accessories, such as tele-converters and extension tubes.
Using the adaptor, the G1 can mount the full range of legacy Four Thirds lenses. However, its smaller size can result in combinations that are less well balanced than would be the case with Four Thirds DSLRs.

Lens Roadmap

Although details are still a little sketchy, Panasonic has released a lens roadmap for Micro Four Thirds (expect something similar from Olympus at some point soon):