Fast lenses seem to be hard to make too (judging by how few are available), which is a shame.

I’ve got a load of fast c-mount lenses on the way to play with.

Not sure why 4/3 is called 4/3 but I doubt it’s because it’s 4/3

It’s four thirds of an inch, IIRC. I think that’s still an equivalence to something rather than an absolute measurement though.

It’s four thirds of an inch, IIRC.

yes, measured round the outside of the vacuum tube containing the original vidicon sensor 🙂

Ah, should’ve done this first.

http://en.wikipedia.org/wiki/Four_Thirds_system

The name of the system stems from the size of the image sensor used in the cameras, which is commonly referred to as a 4/3″ type or 4/3 type sensor. The common inch-based sizing system is derived from vacuum image-sensing video camera tubes, which are now obsolete. The imaging area of a Four Thirds sensor is equal to that of a video camera tube of 4/3″ diameter.
…
In an interview John Knaur, a Senior Product Manager at Olympus, stated that “The FourThirds refers to both the size of the imager and the aspect ratio of the sensor”.[7] He also pointed out the similarities between 4:3 and the standard printing size of 8×10 as well as medium format 6×4.5 and 6×7 cameras, thus explaining Olympus’ rationale on choosing 4:3 rather than 3:2.

They should have let the firmware team name it. It would have been called Panther.

Also relates to the aspect ratio of the sensor (or rather has conformed to it). The old 35mm film days the negative size was 36mm x 24mm hence being a ratio of 3×2 or 3/2. Hence this recognised standard being used across the variety of different full frame and smaller sensors (lost count of how many derivatives are floating about now). There is talk of the higher end Canons dropping this aspect and going to a square format to better utilise the light circle.

Hence 4/3 sensor size is 17.3×13 which is a 4×3 ratio or 4/3.

Used to be a popular format of old with 6 x 4.5 medium format cameras (still used in the majority of digital backs).

Never knew about the Video camera Tube background … interesting.

He also pointed out the similarities between 4:3 and the standard printing size of 8×10 as well as medium format 6×4.5 and 6×7

4/3 = 1.33
6/4.5 = 1.33
7/6 = 1.16
3/2 = 1.5
10/8 = 1.25

so geometrically, full frame is nearer to 4/3 than 6/7 is 🙂

4:3 is slight more square, no? Which means it’s using more of the round field of view of the lens I suppose. One of the big deals I think was that the sensor was smaller which means the camera is only using the middle of the field of view which is sharper, has less fall-off, less aberration and so on.

I think that’s why all the Oly 4/3 lenses are good.

I think that’s why all the Oly 4/3 lenses are good.

Are they? I understand the logic but I’m not sure it applies.

m4/3 lenses need software correction because optically they’re poor.

4:3 is slight more square, no?

which only matters if the subject matches the format – and how often is that the case ?

All the reviews I read of the Oly 4/3 lenses (not m43) go on about how good they are. Now I know that Oly have always had a reputation for good glass, but I understood that because it’s a system designed purely for digital that helped. I then guessed the above reasons 🙂

Some also has to do with the light path, smaller light circle means less oblique angles at both the element and sensor.

Larger elements are more expensive to manufacture, esp when u start adding flourite etc.

smaller light circle means less oblique angles at both the element and sensor.

only if the lens stays at the same distance – which it doesn’t

Larger elements are more expensive to manufacture, esp when u start adding flourite etc

and yet many 4/3rds lenses seem ridiculously expensive ?

Do they? They seem really cheap for the quality actually.