Four Thirds' Redux: Correcting the misconception
By
Mike Tomkins
(Thursday, October 3, 2002 - 13:21 EDT)
When details of Olympus' plans for its new "four thirds" camera system began appearing in public a year and a half ago, it seems that something was lost in the translation.
In an interview with Olympus executives yesterday afternoon, we learned that the "Four Thirds System" does not refer to a 4/3-inch image sensor that has been presumed to be the base of the design. In fact, Olympus tells us, the cameras will use a sensor with a diagonal measurement of 22.5 millimeters, which by our math converts to roughly 0.89 inches, or in insane fraction-speke, almost exactly 225/254ths (rather more rationally, it is a tad over 7/8ths of an inch). ;)
We're not sure exactly how the confusion arose, but unfortunately Olympus' own recent press release perpetuated it by referring to a "4/3-Inch (Type) Image Sensor Size". As we understand it, this was meant to imply a 4:3 sensor with approximately a one-inch diagonal.
So, why did the 4/3 partners choose this particular imager size and aspect ratio? We were told that the reason was the closeness of 4:3 to the common 8" x 10" print size (a 4:3 imager of appropriate resolution would yield a print size of 8" x 10 2/3"), as well as the match with the 4:3 aspect ratio used on computer monitors. The engineers apparently determined a sensor diagonal of 22.5 millimeters as giving the optimal ratio of lens and body size to image performance.
Keeping the sensor size down allows the back focus distance (the distance between the back of the lens and the sensor's surface) to be closer, making it easier to design sharper lenses which can in turn allow smaller pixel sizes. According to Olympus, most current lenses for 35mm SLRs resolve down to about 10 microns, and top-end lenses to around 6 microns. Lenses for the Four Thirds format, we were told, should theoretically be able to resolve right down to 1 or 2 microns. A second advantage predicted is that the lenses can be much brighter than their 35mm-counterparts.
We asked Olympus about Kodak's involvement, and whether the company would simply be providing imagers or had plans to market cameras and/or lenses for the Four Thirds System as well. The response was interesting; whilst predictably we were referred to Kodak themselves for a definitive answer, we were also told that the agreement companies joining the Four Thirds Forum must sign requires them to "aggressively pursue" development of camera bodies and lenses. If accurate, this would likely see Kodak releasing their own Four Thirds System products, as well as likely being a source of suitable sensors.
So - when can we expect to see the first Four Thirds products? Sadly, we couldn't get a definitive answer on that point. A suggestion that perhaps midway through 2003 might be a reasonable timeframe to expect the first developments was immediately qualified as a "rough guess". As we understand it, the final details of the specification are still being hammered out, and with Olympus, Kodak and Fuji currently involved, further companies - both manufacturers of camera bodies and third-party lenses - are still being approached to ascertain interest in the concept.
Our friends at the Digital Eye website have posted a detailed interview with Olympus discussing the Four Thirds System as well. Watch this space for more on this developing story!
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