The introduction of a mirror-less, almost silent and compact but high image quality, interchangeable lens system that is the Micro Four Thirds has inspired much of the photography world.

It not only has the above features, but its short lens mount to sensor distance means almost any lens ever made can be mounted on it (albeit with 2x crop factor and in manual focus), and the absence of the mirror means manual focus, image aspect ratio selection and very low light AF is now much easier and faster. Not only that but if you use Olympus MFT cameras, you automatically convert all these lenses into image stabilised ones – even tilt-shift or ultra wide angle!

But could a larger sensor system be built that could compete with it?

Now, imagine a 48 megapixel full frame sensor camera that could also do 12mp Micro Four Thirds or Four Thirds with 2x crop factor and use almost any lens ever made – sorry but this is extremely unlikely to ever happen in cross-system AF-capability, but I can dream can’t I?

Let’s have a look at a few issues manufacturers would face:

• edge-to-edge image quality
• the larger the sensor, the more aberrations in the periphery, this is even greater when using short lens mount to sensor distances as with the new Leica M9
• to solve this, the Leica M9 uses a very expensive Kodak sensor with offset microlenses to optimise the peripheral light rays hitting the sensor, at present, this would mean expensive camera, no live view and thus no AF, and the potential for aberration problems with other lens types
• the easiest alternative is to keep the usual 35mm dSLR lens mount to sensor distance, but then you would never be able to use Leica M or Canon FD lenses, nor MFT or Four Thirds lenses, and the camera would be MUCH thicker than a Micro Four Thirds camera
• fast contrast detect AF lenses
• MFT has shown that to achieve fast contrast detect AF, you need a great computer algorithm (such as Panasonic’s), live preview sensor with fast readout rates, extra lens mount communication pins for finer AF control (such as Micro Four Thirds), lens motors and algorithms optimised for contrast detect AF, relatively small lenses that the AF mechanism can rapidly adjust in this iterative manner
• the above pose many hurdles for larger sensor manufacturers, most they can jump if they wish to, but the lens size issue may be the main limiting factor in allowing fast AF
• in body sensor stabilisation
• the bigger the sensor, the bigger the mechanism needed to control sensor image stabilisation and thus potentially a bigger more expensive and noisy camera
• short lens mount to sensor lenses
• no manufacturer other than Leica, Panasonic or Olympus currently makes interchangeable lenses with short lens mount to sensor distances, thus Canon, Nikon, Sony or whoever else would have to embark on a new lens system in addition to their APS-C/DX lens system and the full frame lens system – not something they would look forward to doing, particularly in a global recession
• to not have a short lens mount to sensor distance defeats the prime advantage of a mirror-less system – smaller size cameras
• electronic viewfinder technology
• Panasonic appear to be the leader in EVF technology and the size of their company will tend to keep them as leaders
• video capability
• one of the main advantages of a mirror-less system optimised for contrast-detect AF is that AF-capable video potentially becomes functional
• as even HD video is only about 2mp, there is little more to be gained in jumping to a larger sensor than MFT for video apart from ability to use 35mm lenses at their native focal length, higher ISO capability and even shallower DOF

Thus, such a camera could technically be built, but at substantial cost, R&D, and in the end, it would be necessarily bigger, heavier and more expensive than Micro Four Thirds, and necessitate a new range of dedicated AF lenses which are likely to AF slower than MFT given the size of the glass in them.

It is unlikely a full frame camera would be much smaller than the Leica M9 – much bigger than MFT.

Whilst such a camera may offer greater image quality (although likely to be worse in the periphery), especially at high ISO, and allow legacy 35mm lenses to be used at their native focal length, the whole point of a mirror-less system would seem to be lost when compared to the compact size of MFT.

Given that neither Canon nor Nikon have created great pro quality lenses dedicated for their extremely popular cropped sensor dSLR cameras, it would seem that they would be unlikely to create a dedicated superb lens system as Panasonic and Olympus have done for their MFT (still evolving) and FT cameras.

I have dreamed of having a 48mp 35mm full frame sensor system with short lens mount to sensor distance that could be used with any lens system – even MFT via an AF-capable adapter giving a 12mp 2x crop, but then could be also be used in full frame with full frame lenses via appropriate AF-capable adapters.

My dream of having in effect a universal 35mm full frame digital back that could be used for most lenses ever made including Leica M, Canon FD, Four Thirds and MFT in a cost-effective and functional system is likely to stay that way in the next 5-10 years at least (and unfortunately, I can’t see AF-capable adapters ever eventuating) – a dream.

I can imagine Canon and Nikon producing fixed lens mirror-less cameras with APS-C or full frame sensors in the near future but not an interchangeable lens system, but Sony may be a different story – Sony with their company size (albeit half that of Panasonic as I understand it), and substantial expertise in video systems, may create a full frame version of the Panasonic GH-1 by 2011, but it is unlikely to have a short lens mount to sensor distance and will probably only take Sony/Minolta 35mm lenses and it will likely be as big as their full frame dSLRs.