Posted by Richard Crowley on 09/07/06 16:14

"Rick Merrill" <rick0.merrill@NOSPAM.gmail.com> wrote in message
news:rL-dnRtQBKQ53p3YnZ2dnUVZ_oKdnZ2d@comcast.com...
> Richard Crowley wrote:
>
>> Acurajustin1978 wrote ...
>>
>>>I know what a CCD is... but when I see the sizes listed it will say
>>>something like 1/6 or 1/7.5.
>>>What does this mean? One sixth of an inch?
>>>Obviously I'm guessing bigger is better.
>>
>>
>> It is the *diagonal* measurement of the imaging surface,
>> measured in inches (for better or for worse). It is measured
>> diagonally because lenses are round and that is the *diameter*
>> of the image that must be delivered by the lens.
>>
>> Bigger means more sensitive imaging devices (because
>> there are more photons hitting each "pixel" to turn into
>> an electrical signal). However, bigger also means larger
>> (and significantly more expensive) lenses to deliver an
>> appropriate image to the chip.
>
> Mmmm, I think you are on to something: the round lense image must
> fit INSIDE the square CCD; therefore it would make more sense for
> the CCD to be measured along it's edge: the diameter of the round image
> that would just fit.
>
> So I think CCD is measured square, not diagonal like the big screens.

I think you have it backwards. The diagonal of the chip
must fit inside the circle image produced by the lens.

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