V1/V2 vs OM-D E-M10 (take 2)

Started 5 months ago | Discussions thread
Eamon Hickey
Veteran MemberPosts: 3,161
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why they did it
In reply to MarsObserver, 5 months ago

MarsObserver wrote:

dmaclau wrote:

On another note, anyone know why they call the sensor 1"? It's not.

The term dates waaaaaay back to the time of television tubes.

Something about the actual, usable sensor size being 16mm per each 1" of a TV tube.

Yes, a vidicon tube with a 1" diameter (i.e. the diameter of the glass tube) had an actual imaging area (i.e. the photo-receptor inside the tube) of 13.2 x 8.8 mm (16mm diagonal), which is known as the 1" or 1"-type sensor size.

How that got adopted by cameras I'm not sure other than TV, video and stills are all intermingled (like the development / introduction of 35mm film.) Video is, after all, just 'moving pictures'

It happened because complete optical systems had been built in front of the vidicon tubes in all sorts of applications, many of them custom applications -- television, yes, but also surveillance (i.e. closed-circuit TV), machine vision and inspection, especially inspection on production lines, etc. When applications engineers began to replace the vidicon tubes with solid-state sensors (i.e. CCDs) they needed to know what CCD they could buy to put behind their already existing optical systems and get the same imaging performance (i.e. same field-of-view, same depth-of-field etc.) as they got from the old vidicon tube. So the CCD sizes were specified in terms of the size of the vidicon tube they could replace without changing your optical set up. i.e: "If you were using a 1" vidicon tube, replace it with this CCD, which we'll also call 1", or 1"-type, to make it simple."

Hope that makes sense. Obviously, there's no longer any need whatsoever to hold on to this old engineering convention, but such things die hard.

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