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Sensor size maths

Forum Digital Camera : Digital SLR - Sensor size maths

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Archived from groups: rec.photo.digital.slr-systems (More info?)

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

Add a reply

Archived from groups: rec.photo.digital.slr-systems (More info?)

nospam wrote:
[]
> 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/?/Gl [...] zes_01.htm

David

Reply to Anonymous

Archived from groups: rec.photo.digital.slr-systems (More info?)

>See:
> http://www.dpreview.com/learn/?/Gl [...] zes_01.htm
>
>David
>
>

Thanks for that.

I can now put my calculator away.

--

Reply to Anonymous

Archived from groups: rec.photo.digital.slr-systems (More info?)

"nospam" <nospam@nospam.demon.co.uk> wrote in message
news:x244vUOMrGwCFw2q@cobe.demon.co.uk...
> >See:
>>
>> http://www.dpreview.com/learn/?/Gl [...] zes_01.htm
>>
>>David
>>
>>
>
> Thanks for that.
>
> I can now put my calculator away.
>
It gets confusing when they start using decimal fractions 1/2.5" instead of
metric.

Reply to Darrell

Archived from groups: rec.photo.digital.slr-systems (More info?)

Darrell <spam@this.eh> writes
>
>"nospam" <nospam@nospam.demon.co.uk> wrote in message
>news:x244vUOMrGwCFw2q@cobe.demon.co.uk...
>> >See:
>>>
>>> http://www.dpreview.com/learn/?/Gl [...] zes_01.htm
>>>
>>>David
>>>
>>>
>>
>> Thanks for that.
>>
>> I can now put my calculator away.
>>
>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.

Reply to Anonymous

Archived from groups: rec.photo.digital.slr-systems (More info?)

In article <L7M70wAWMKwCFwQE@nospam.demon.co.uk>,
nospam <nospam@nospam.demon.co.uk> wrote:
>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.
--
Email: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Reply to Anonymous

Archived from groups: rec.photo.digital.slr-systems (More info?)

"nospam" <nospam@nospam.demon.co.uk> wrote in message
news:L7M70wAWMKwCFwQE@nospam.demon.co.uk...
> Darrell <spam@this.eh> writes
> >
> >"nospam" <nospam@nospam.demon.co.uk> wrote in message
> >news:x244vUOMrGwCFw2q@cobe.demon.co.uk...
> >> >See:
> >>>
> >>>
http://www.dpreview.com/learn/?/Gl [...] zes_01.htm
> >>>
> >>>David
> >>>
> >>>
> >>
> >> Thanks for that.
> >>
> >> I can now put my calculator away.
> >>
> >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.

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.

Reply to Anonymous

Archived from groups: rec.photo.digital.slr-systems (More info?)

Darrell wrote:
> "nospam" <nospam@nospam.demon.co.uk> wrote in message
> news:x244vUOMrGwCFw2q@cobe.demon.co.uk...
>>> See:
>>>
>>> http://www.dpreview.com/learn/?/Gl [...] zes_01.htm
>>>
>>> David
>>>
>>>
>>
>> Thanks for that.
>>
>> I can now put my calculator away.
>>
> 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

Reply to Anonymous

Archived from groups: rec.photo.digital.slr-systems (More info?)

Paul H. <xxpaulhtck@zzcomcast.yycom> wrote:

>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".

--
Ken Tough

Reply to Anonymous

Archived from groups: rec.photo.digital.slr-systems (More info?)

In message <d9qd86$77j$1@Fuego.d-and-d.com>, DoN. Nichols <dnichols@d-
and-d.com> writes
>In article <L7M70wAWMKwCFwQE@nospam.demon.co.uk>,
>nospam <nospam@nospam.demon.co.uk> wrote:
>>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.

It all makes sense now.

thanks

--

Reply to Anonymous

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