Sensor sizes

Started Jul 21, 2014 | Questions thread
boxerman Senior Member • Posts: 1,413
Re: Sensor sizes

This is where some of those incredibly boring historical accidents have become a permanent feature of "modern" specs. In this case, sensor sizes were modeled on (TV) tube technology, where the sensibly active area of the tube is about 2/3 of the outside diameter (OD) of the tube. (Using the edge of the tube I assume would introduce shape artifacts from rounding, or possibly pose manufacturing problems.) So, a 1" sensor means one inch, but that refers to the OD of the (nonexistent) tube that might contain an active area the same as that sensor.  SO...

jimbrobb wrote:

Looking at the new Panasonic fz1000 and the sensor is described as 1". Is that 1 inch?

Yup, but it's the OD of the non-existent tube. So, the ACTUAL sensor is about 2/3s of that, which is about 16mm. Close enough (to 15 mm you computed) for jazz.

Also, why is the four thirds cameras described as such.

Same deal. 4/3 of an inch. But, that refers to the nonexistent tube, so the sensor is actually about 2/3 of that, or about 22.5 mm.

You can read about it here:

Sensor Sizes

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The BoxerMan

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