What is Micro Four Thirds?

It is important to understand that Micro Four Thirds uses the exact same sensor as four thirds; there is no size reduction in the sensor. When compared to the Four Thirds System standard, the primary differences in the Micro Four Thirds System are:

  1. Approximately 50% shorter flange back distance (mount-to-sensor distance): With the optical SLR viewfinder replaced by an LCD or EVF (electronic view finder) - or both - the mount to sensor distance can be cut in half. This allows the lens to be designed without a back-focus requirement, which also greatly reduced the size.

  2. 6mm smaller lens mount outer diameter: Without the need for so much back-focus in lens designs for Micro Four Thirds, the diameter of the lens flange can be reduced, while still allowing designs for parallel light paths.

  3. Electrical contacts in mount increased from 9 to 11: With viewfinder optics replaced by electronics, more electronic interfaces to the lens are required.

When the standard was announced, Olympus and Panasonic emphasized the compatibility of Micro Four Thirds with the current Four Thirds system and lenses. Micro Four Thirds, like Four Thirds, is also an open system that can be licensed by any manufacturer who wishes to use it.

Four Thirds Compared

The Four Thirds standard is one of the smaller of the formats based on APS-C, but it is still about 75% of the area of the Canon XSi. However, compared to P&S sensors the Four Thirds sensor is huge.

DSLR Sensor Comparion
Camera Effective
Sensor Area and Dimensions % of Full-Frame Sensor Density
Olympus SP-579UZ 10.0 6.13x4.60
0.28 cm2
3.20% 36
Canon G9 12.1 7.60x5.70
0.43 cm2
5.10% 28
Panasonic G1 12.1 13.5x15
2.43 cm2
28.10% 4.98
Olympus E-520/E-3 10.0 13.5x18
2.43 cm2
28.10% 4
Canon XSi 12.2 14.8x22.2
3.28 cm2
38.00% 3.7
Sony A350 14.2 15.8x23.6
3.72 cm2
42.90% 3.8
Pentax K20D 14.6 15.6x23.4
3.65 cm2
42.20% 4
Canon 50D 15.1 14.9x22.3
3.32 cm2
38.40% 4.5
Sony A700, Nikon D300, Nikon D90 12.3 15x23.5
3.66 cm2
42.40% 3.3
Nikon D700/Nikon D3 12.1 24x36
8.64 cm2
100% 1.4
Canon 5D 12.7 24x36
8.64 cm2
100% 1.5
Canon 1Ds Mark III 21.1 24x36
8.64 cm2
100% 2.4
Sony A900 24.6 24x35.9
8.61 cm2
100% 2.9

If you have any doubt why the photo market has been moving to DSLR from P&S you have only to look at the last column detailing sensor density. At 12.1MP, the new Panasonic G1 will establish a new density high in the DSLR market at almost 5MP per cm2. However, the top-of-the-line Canon G9 P&S at 10MP has a tiny sensor by comparison and the density is 28 MP/cm2. The Olympus Super Zoom SP-570UZ is even worse at 36 MP/cm2.

The motivation for Micro Four Thirds should be crystal clear in this chart. Panasonic and Olympus are trying to extend their Four Thirds sensor technology to higher-end, higher-quality, but very small and pocketable interchangeable lens cameras. These new cameras will feature large hi-res LCD screens, full time Live View, and fast contrast-detect focusing. The top ones will also feature hi-res EVF, and video capabilities are mentioned in the Micro Four Thirds standard. It should be clear the idea is a new bridge technology that brings DSLR features, P&S features, and camcorder features together in a more compact and cheaper camera body.  In doing this they will create a new camera class, or chart directions for future interchangeable lens cameras, depending on market acceptance.

Index Panasonic G1 Press Release


View All Comments

  • computerfarmer - Thursday, November 27, 2008 - link

    There is a detailed review at the following site.

    It is compared with Nikon D90/D60, Olympus 520, Canon Rebel XSi(450).

    I would like to see this camera with the 2 lens kit.
  • steveyballme - Tuesday, September 16, 2008 - link

    The Iraqi scientists in tha basement almost have the ZuneCan ready. Don't be too hastey about getting one of these things!

  • aeternitas - Monday, September 15, 2008 - link

    http://www.dpreview.com/previews/panasonicG1">http://www.dpreview.com/previews/panasonicG1 Reply
  • whatthehey - Monday, September 15, 2008 - link

    It's amazing that no one else can manage to get pre-release digital cameras (particularly DSLR) other than dpreview. I mean, it's almost like they're owned by some company that has early access to hardware, and they use that to gain an advantage. Oh, wait....


    Now the only question is whether their integrity is compromised by the ownership. At the very least, they have an effective monopoly on digital camera previews, which is rather disconcerting. What I don't understand is why the camera companies don't want other sites to get in on the action. It's almost like they're stuck in a pre-digital world trying to figure out how to cope with the internet.

    Marketing: "Hey, we should send out a bunch of camera samples to web sites. They'll provide reviews, which are essentially free advertising! All it costs us is shipping plus the hardware, which is a damn sight cheaper than any other form of advertising (and more effective to boot)."

    Marketing VP: "HELLS NO! We can't let anyone have early access to our product! It will kill our profits! THINK OF THE CHILDREN!"
  • Wesley Fink - Monday, September 15, 2008 - link

    Thanks for your comment. You certainly understand our frustration in trying to get camera info and samples to review. Frankly we have asked every manufacturer repeatedly, but we have yet to review even ONE camera provided by a manufacturer. We have been buying the cameras wherever we can as fast aswe can and then reselling them after review.

    The manufacturers keep saying nice things over the last two years, but none of them has ever delivered anything for review. It is still pulling teeth just to get on and remain on, press release lists. This is certainly totally unlike our presence in the computer market and it can be quite frustrating.

    We do think our perspective on electronics is quite different from other imaging review sites and we hoped that some manufacturers would see that as a new opportunity for a fair and frank review. Perhaps over time that will eventually happen.
  • aeternitas - Monday, September 15, 2008 - link

    I think it would help manufacturers have a greater trust in the sites review abilities if there was some sort of standard you guys came up with when reviewing them. Resolution cards, constant scenes in consistent lighting that can be taken to show differences in different ISO settings to build a database against other cameras.

    It has not seemed yet like the reviews have any sort of constants to compare other reviewed cameras here against. Color, sharpness, noise true resolution ect ect. One can put the coolest name they want on their image processor but the outcome is what matters, and it’s too hard to compare totally different scenes with the help of impractical numbers.

    Controlled consistant scenes + onmouseover images for the review itself = your friend.
  • slashbinslashbash - Monday, September 15, 2008 - link

    The benefit of SLR's in the film world was obvious. The importance of the "Single Lens" in the "Single Lens Reflex" equation was obvious. What you see in the viewfinder = what will be imaged on the film. In the digital world, with live view screens showing the actual sensor image even more precisely than most optical DSLR viewfinders (only the most expensive have 100% viewfinders), there is no longer any need for the "reflex" part of the "SLR" construction. That whole flipping-mirror thing was just a workaround, a hack, a kludge. Panasonic is the first to realize this, and create a digital camera with interchangeable lenses that opens up the full range of possiblities for digital imaging. The mirror box meant that there would always be a gap of some 20mm (more or less) from the sensor to the back of the lens; thus making lenses with focal lengths of less than approx. 20mm extremely difficult to engineer. Now that the mirror box is gone, the lens can get much closer to the sensor, and hugely wide angles should be attainable, even on a relatively small sensor like the 4/3rds. Reply
  • strikeback03 - Tuesday, September 16, 2008 - link

    I don't like any previous EVF I have seen, but I'll reserve judgement on this until I have actually looked at one. The DPR preview said it got grainy when gained up a lot at night, have to see how bad that really is compared to an optical viewfinder. Same with the autofocus - they say it is fast, but I want to see how fast and accurate it is.

    SLRs typically have a registration distance of around 40mm, this halves that to 20mm. So anything wider than 20mm (which isn't wide on 4/3) will be retrofocal, and to beat the current widest rectilinear lens (Sigma 12-24 on film/FF digital) they will need a lens wider than 6mm.

    For whoever said they want a more rangefinder shape, I'm sure that could be done, but their product research probably said the more traditional shape would sell better. Sales of the Olympus E300/E330 were not helped by being a somewhat non-traditional layout.
  • Maxington - Tuesday, September 16, 2008 - link

    " In the digital world, with live view screens showing the actual sensor image even more precisely than most optical DSLR viewfinders"

    Except electronic viewfinders bring their own parcel of problems.

    I just wish they'd stop with the half-assed semi-DSLR body shape and size, and go straight for a very compact, rectangular rangefinder size mobody.

    I don't want a slightly smaller DSLR, or I would've bought the Olympus E420. I want a digital rangefinder that doesn't suck and cost the earth like the Leica M8 does.
  • AnnihilatorX - Tuesday, September 16, 2008 - link

    Read the review by dpreview.com

    I haven't see a single bad thing about live view so far.

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