Sensor size maths

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nospam - 27 Jun 2005 16:25 GMT

Hi,

I read some very informative information at

http://www.photozone.de/3Technology/digital_1.htm

But I don't understand the mats behind it.

I thought a 1/2.7" sensor meant that it was one sensor 2.7 inches in
diagonal.

But that is obviously nonsense. Maybe its a fraction of some sort or the
number of dia in the construction!!

The 1/1.8" sensor is bigger than the 1/2.7" sensor !

so how do I work out the size of a sensor from the figures given.
I know the sizes are given at the bottom of the web page, I just want to
understand the maths.

thanks

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David J Taylor - 27 Jun 2005 19:07 GMT

[]

> The 1/1.8" sensor is bigger than the 1/2.7" sensor !
>
> so how do I work out the size of a sensor from the figures given.
> I know the sizes are given at the bottom of the web page, I just want
> to understand the maths.

See:
http://www.dpreview.com/learn/?/Glossary/Camera_System/Sensor_Sizes_01.htm

David

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nospam - 27 Jun 2005 22:08 GMT

>See:
> http://www.dpreview.com/learn/?/Glossary/Camera_System/Sensor_Sizes_01.htm
>
>David

Thanks for that.

I can now put my calculator away.

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Darrell - 28 Jun 2005 00:44 GMT

> >See:
>>
[quoted text clipped - 5 lines]
>
> I can now put my calculator away.

It gets confusing when they start using decimal fractions 1/2.5" instead of
metric.

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nospam - 28 Jun 2005 02:08 GMT

Darrell <spam@this.eh> writes

>> >See:
>>>
[quoted text clipped - 8 lines]
>It gets confusing when they start using decimal fractions 1/2.5" instead of
>metric.

I'm not still not sure what a decimal fraction such as 1/1.8" is in
millimetres, not sure it really has a conversion value.

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DoN. Nichols - 28 Jun 2005 03:39 GMT

>Darrell <spam@this.eh> writes

[ ... ]

>>It gets confusing when they start using decimal fractions 1/2.5" instead of
>>metric.

>I'm not still not sure what a decimal fraction such as 1/1.8" is in
>millimetres, not sure it really has a conversion value.

    Sure it does:

    1/1.8" = 0.5556" (to four significant figures) -- simply divide
            as shown.
    0.5556" = 14.11mm (again to four significant figures)
            Multiply by 25.4 -- the number of mm in an
            inch to calculate mm.

    FWIW -- most micrometers read directly to 0.001" or to 0.02mm.
Verniers allow an extra order of magnitude, but for our purposes, there
is little need to really go even to the four significant figures which I
did use.

    Enjoy,
        DoN.

Signature

Email: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564
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nospam - 28 Jun 2005 15:15 GMT

>>Darrell <spam@this.eh> writes
>
[quoted text clipped - 21 lines]
> Enjoy,
> DoN.

It all makes sense now.

thanks

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Paul H. - 28 Jun 2005 04:57 GMT

> Darrell <spam@this.eh> writes
> >
> >> >See:

http://www.dpreview.com/learn/?/Glossary/Camera_System/Sensor_Sizes_01.htm

> >>>David
> >>
[quoted text clipped - 7 lines]
> I'm not still not sure what a decimal fraction such as 1/1.8" is in
> millimetres, not sure it really has a conversion value.

These odd-looking designations really have little to do with the sensor
size, at least directly. See

http://www.dpreview.com/learn/?/key=Sensor_Sizes

for details. It's actually one of those idiotic engineering designations
which has long since outlived its frigging utility, like measuring mass in
"slugs". I had to take several engineering courses as electives in college
and was always glad to get back to the physics department and the good old
MKS system because, for some odd reason, it always seemed somehow saner to
measure velocity in meters per second instead of furlongs per fortnight.

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Ken Tough - 28 Jun 2005 09:33 GMT

>These odd-looking designations really have little to do with the sensor
>size, at least directly. It's actually one of those idiotic engineering designations
>which has long since outlived its frigging utility, like measuring mass in
>"slugs".

I imagine the continued use in digital cameras has more than a little
to do with the marketing department. They probably don't want it to
be too easy for people to compare sensors in the p&s market, and I've
known a few people who assumed 1/2.7" was bigger/better than 1/1.8".

Signature

Ken Tough

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David J Taylor - 28 Jun 2005 07:53 GMT

>>> See:
>>>
[quoted text clipped - 8 lines]
> It gets confusing when they start using decimal fractions 1/2.5"
> instead of metric.

Indeed it does, and even more so when you realise that the size is
actaully the size of the surrounding (hypothetical) glass tube. I'm all
in favour of quoting real sizes (e.g. 8.8 x 6.6mm) and that's exactly what
I do now.

Cheers,
David

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