In response to a misconception voiced in another article, http://www.metricviews.org.uk/2007/08/28/photo-paper-sizes/#comment-4192 , it may surprise some readers to learn that the image sensors in Four Thirds digital cameras do not have a diagonal size of four thirds of an inch.
[Article by Martin Ward]
The naming of the Four Thirds camera system is a good example of a practice that is often used when a manufacturer wants to hide the true size of a product from the consumer. Namely, an obscure or deceptive imperial measuring convention is used instead of the original metric design size. The image sensors in Four Thirds cameras are actually 18 mm x 13.5 mm (22.5 mm diagonal), with an imaging area of 17.3 mm x 13.0 mm (21.6 mm diagonal) – quite a lot smaller than a diagonal size of four-thirds of an inch (33.9 mm), and significantly smaller than the 22.5 x 15.0 mm and 23.6 mm x 15.8 mm sensors used in the equivalent cameras of competitors Canon and Nikon.
The practice of describing image sensors in this deceptive manner continues from the days when all image sensors consisted of vacuum tubes and were described by the physical diameter of the glass tube, which was always larger than the “diameter” of the image sensor inside. Thus the imaging area of a Four Thirds camera sensor (17.3 mm x 13 mm) is the same as the imaging area of a hypothetical vacuum image-sensing tube of 4/3 inch diameter.
As with LCD and plasma TVs, technology has changed beyond the point where it makes any sense to continue using the old measuring conventions. It would be far more useful to modern consumers to describe the sizes of TV screens and camera image sensors in terms of width x height in standard metric units, than in terms of the diameters of hypothetical vacuum tubes, especially when these products now come in different aspect ratios. But, as is often the case, the needs of consumers do not always coincide with those of the marketing departments of manufacturers.
Further information on the Four Thirds system can be found at
I am in total agreement with the Author here that flat screen technology should herald a move toward an open and honest specification of screen size. There is no excuse what-so-ever for the continued and outdated parameter of screen diagonal, especially when quoted in inches.
It is difficult enough to decide what size TV to buy when all you hear or see is a single measurement that bears no comparison with tyical CRT TV, the like of which you intend to upgrade.
It’s time to move to a single system of measurements for all aspects of product description. Screen viewing rectangle and physical cabinet dimensions can be understood by all consumers. They have an inalienable right to make properly informed purchasing decisions based on easily understood and honest measurement data.
The metric system is now the only honest system around. All others are subject to obscure variations that are being maintained by a conspiracy among traders in the retail sector who care little for social and economic responsibility.
From the history of marketing it has been a common practice to make measurements as difficult to understand as possible. It is not in the interest of a company to make it easy for you to compare.
For this reason I can’t see the industry voluntarily going to adapt any means to make life simple by going to X-Y descriptive type of measurement or switching away from inches, unless it is made a law.
Some of us notice that the inches don’t match the real size, especially when the product is designed, engineered and manufactured to millimetre specifications.
In the past it was common for governments to step in and pass laws to make things easier for consumers. Those days seem to be slipping by as such laws interfere in a businesses right to market its products any way it seems fit. The right to allow confusion is not in the interest of the buyer, but the seller who uses the confusion to increase sales.
Here is another example of where imperial is being introduced into the German market and permitted despite the confusion it will bring to consumers. It is allowed because it would inhibit the free flow of goods.
http://www.earthtimes.org/articles/show/118646.html
Before globalization, German TVs were always described in centimetres, now with imports from Asia, the inch has been introduced. Germans don’t know inches and pints, so that makes it perfect for them to purchase something that turns out to be different then what they thought they were getting. Don’t be surprised if under the guise of the “free flow of goods”, that litre sized products are replaced in Europe by the 946 mL size.
The metric will stay, but the amount will be made to prevent a consumer from being able to spot a bargain in another brand.
I would never have thought in my dreams that I would have to see the day on which the EU turns against the system of units used by all except one EU member state. Ireland is largely metric. It is one thing to allow a derogation for the British Isles, but it is certainly another thing when the European Court forces metric EU member states to accept British units in disguise. I can only hope that Diageo will leave it that. Its large size of Baileys is in 750 mL bottles. Let’s hope that will not become 30 fl.oz with an oddball metric indication added in the near future.
This is simply a tactic for confusing clientel. Why would a company ever want standard sizes? That would make it too easy for price comparisions. The US has been doing it for years. It’s a shame to hear the EU is caving to the demands of a very small, yet very vocal minority. Metric makes us immune to market deceptions. The US still uses FFU for this very reason.
I hate to see the EU turn its back on Metric. Lets just hope that Metric doesn’t turn its back on them.
Where did any of you get the idea that the 4/3 system has anything to do with the sensor size being four one thirds of an inch in size? It doesn’t and the originator of the four thirds system, Olympus, never has or had any intention of pulling the wool over anyone’s eyes nor is it “simply a tactic for confusing clientel.�
The choice of four thirds by Olympus had nothing to do with imaging sensor size initially. Four thirds is an aspect ratio that they chose to use for a new camera sensor and mount system. 4/3 is simply an aspect ratio that can also be defined as 1:1.33. Whether it is in inches, meters, feet, etc. means nothing. With such an aspect ratio then if one axis (x) is 1 meter long then axis y will be 1.33 meters long, or it could be in inches, feet, etc. It is the same as with 16/9 for HD TV, it’s simply an aspect ratio. 16/9 HD TV’s come in many sizes, don’t they? Olympus chose the four thirds aspect ratio and then chose a size to make a four thirds sensor in. As far as I know it had nothing to do with old vacuum tube sizes, either. Again, 4/3rds isn’t a size, it is an aspect ratio.
Olympus is anything but deceptive. Their goal with four thirds was viewed as a systems goal, so four thirds (4/3) should actually be viewed in that respect. They designed not just a sensor size that they felt was an optimum size for a digital SLR camera, they designed a complete mounting system, electrical camera/lens interface system, camera lens mount to sensor surface dimension, etc. that they would offer as open source i.e., not proprietary. Anyone that wants to can have access to the design so that they can make their own camera and lenses that will be compatible with any other four thirds camera. Canon and Nikon can have access to the design if they wanted to build a four thirds system camera or lens. I think that is innovative thinking on behalf of Olympus.
So now we have DSLR cameras coming from not just Olympus but Panasonic and Leica too. And lenses from those three plus Sigma and others will be coming; I believe Samsung has something on the boards for four thirds too. Now I am no longer restricted to using only Olympus lenses of my Olympus DSLR if I want to retain the cameras full functionality, I can buy Leica lenses or Panasonic, or Sigma. That to me is a sweet deal because I happen to like Olympus cameras but prefer Leica glass.
In answer to Don B, The official Four Thirds web site explains the meaning of the 4/3.
http://www.four-thirds.org/en/contact/faq.html
“What is the Four Thirds System standard?
It is an open standard for the design of lenses for use in digital SLR cameras with 4/3-type image sensors …”
“What the 4/3 means ?
The Four Thirds System uses a 4/3-type image sensor … the 4/3-type image sensor is twice the size of the 2/3-type sensors used in most digital cameras …”
The name clearly comes from the four-thirds of an inch image sensor and not the four:three aspect ratio of the images that the cameras produce.
However, the main point of the article was that most people would expect a 4/3″ image sensor to be 4/3″ (33.9mm) in size. The fact that a 4/3″ image sensor is actually considerably smaller (17.3mm x 13mm) is, to say the least, not helpful to consumers looking to compare image sensor sizes with other products that advertise the true dimensions of their image sensors (in millimetres).
A table listing the array of confusing inch-based image sensor sizes used in digital cameras and their true dimensions can be found at the following link.
http://en.wikipedia.org/wiki/Image_sensor_format#Table_of_sensor_sizes