Why are CCDs and CMOS video image chips measured in thirds of inches, or even compound fractions like _

Question

1/2.9 (one two-point-ninth) or 1/2.7 (a two-point-seventh), instead of just some kind of simpler number like either the closest standard even fraction of an inch (like a set of 32nds or 64ths, such as 21/64), or simply .33 inches (for 1/3 inches) or .34" (for 1/2.9) or .37" (for 1/2.7 inches)? Or why don't they just use metric measurements for those chips, which, in mm or cm would probably sound less complicated than "one two-point-seventh of an inch"?

Or BETTER YET, if they already make a simple 1/2" chip, why don't they just also make the smaller versions (1/3, 1/2.9, 1/2.7, etc.) so that they measure to the more standard fractions of inches (even more standard than 32nds or 64ths, such as 16ths or 8ths), such as 3/8" (which is just 6/16 instead of the 5.33/16" that 1/3" is)?

Hey, will you come back and see my responses to your answers, please?

Thanks.

Answer 1

it is a carry over from the 1960s when the image pickup element was a round tube. the most common TV pickup tube was 2/3 inch class and consumer was 1/3 inch. A 2/3 inch vidicon could use the same lenses as 16 mm film cameras which were popular with TV stations in the days before they could shoot videotape in the field. i had a video camera with 2/3 inch newvicon and c-mount lenses once. The c-mount or cine, was a common way to interchange 16mm movie lenses. interchangeable lenses were very important in the days before the zoom was perfected.