Making sense of the sensor size?

On Wed, 29 Aug 2007 10:28:15 -0500, RPS <rps RemoveThis @null.void> wrote:

>Could somebody please explain the jargon used to denote the sensor size?
>I mean numbers like 1/1.7. How does this translate to actual size
>(dimensions or area)?
>
>What is the typical size for DSLR?
>For ZLR?
>For good P&S?
>
>Thanks.


I'm not familiar with ZLR and P&S's, but for DSLRs, unless the
manufacturer says the sensor is "full frame", they're usually in the
range of the reciprocal of 1.5 to 1.7... meaning they are smaller
than the standard 35mm from film days. You'll also hear of "APS"
size sensors, a size of film also smaller than 35mm.

That should help you some...


Jim
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bugbear wrote:
> Gisle Hannemyr wrote:
>> This designation has clearly stuck
>> (although it should have been thrown out long ago).
>
> I suspect the manufacturers are happy for the
> size to be obscure, since people
> might find the actual sizes disconcerting.
>
> There's nothing to stop manufacturers
> putting sensor dimensions in
> "normal units" in their brochures, advert
> or manuals, and yet they don't.
>
> BugBear

I suspect your suspicions are accurate. Attempting juggle sensor size,
zoom range, noise and mp value is something they probably prefer to do
behind closed doors where they can better balance value vs hype.
Dave Cohen
 >> Stay informed about: Making sense of the sensor size? 

james.TakeThisOut@jamesphotography_nospam.ca wrote:
> On Wed, 29 Aug 2007 10:28:15 -0500, RPS <rps.TakeThisOut@null.void> wrote:
>
>
>>Could somebody please explain the jargon used to denote the sensor size?
>>I mean numbers like 1/1.7. How does this translate to actual size
>>(dimensions or area)?
>>
>>What is the typical size for DSLR?
>>For ZLR?
>>For good P&S?
>>
>>Thanks.
>
>
>
> I'm not familiar with ZLR and P&S's, but for DSLRs, unless the
> manufacturer says the sensor is "full frame", they're usually in the
> range of the reciprocal of 1.5 to 1.7... meaning they are smaller
> than the standard 35mm from film days. You'll also hear of "APS"
> size sensors, a size of film also smaller than 35mm.
>
> That should help you some...
>
>
> Jim
>
>


There are technical barriers for making full size (35MM double frame)
sensors and there was a good write up when Leica built a digital M
series camera and the compromises that had to be taken. Unfortunately,
I forgot where I read it...

JT
 >> Stay informed about: Making sense of the sensor size? 

james RemoveThis @jamesphotography_nospam.ca wrote:
> On Wed, 29 Aug 2007 10:28:15 -0500, RPS <rps RemoveThis @null.void> wrote:
>
>
>>Could somebody please explain the jargon used to denote the sensor size?
>>I mean numbers like 1/1.7. How does this translate to actual size
>>(dimensions or area)?
>>
>>What is the typical size for DSLR?
>>For ZLR?
>>For good P&S?
>>
>>Thanks.
>
>
>
> I'm not familiar with ZLR and P&S's,

I wouldn't worry too much about digital "ZLR" cameras, the only two ever
made were the Olympus E-10 and E-20.
They are both fixed zoom lens DSLR cameras with a 2/3" CCD sensor, with
a fixed in position image-splitter prism in place of a moving reflex
mirror that a normal DSLR has, so the viewfinder doesn't black out when
a picture is taken.
Any sort of digital camera which has no optical reflex finder (prism or
mirror) is either an EVF digicam or a P&S digicam, any other claim to
name is pure marketing hype.

> but for DSLRs, unless the
> manufacturer says the sensor is "full frame",

As in full-frame 135 (AKA 35mm film), or a digital sensor which has a
sensitive area that is 24x36mm

> they're usually in the range of the reciprocal of 1.5 to 1.7...
> meaning they are smaller than the standard 35mm from film days.

Which is where the term "crop factor"or "zoom factor" came from.
By using the same lens on the smaller than full frame sensor the camera
is cropping off the edges of the image and effectively zooming in by the
crop factor (eg: on a Pentax K10D, with a sensor crop factor of 1.5x a
50mm lens effectively acts like a 75mm lens, as far as angle of view is
concerned)

> You'll also hear of "APS" size sensors, a size of film also
> smaller than 35mm.

A good example is the sensor used in the Canon EOS 400D, it is decribed
as an APS-C and has a crop factor of 1.6x
Then again, the Nikon D40 also has an APS-C sensor, but has a crop
factor of 1.5x
There really is no fixed definition of what size an APS sensor actually
is, but it's usually in the zone between 2/3 to 3/4 (not related to
FourThirds, ratio is just co-incidental) that of a full 135 frame.
 >> Stay informed about: Making sense of the sensor size? 

dj_nme <dj_nme RemoveThis @hotmail.com> writes:
> james RemoveThis @jamesphotography_nospam.ca wrote:

>> You'll also hear of "APS" size sensors, a size of film also
>> smaller than 35mm.

> A good example is the sensor used in the Canon EOS 400D, it is
> decribed as an APS-C and has a crop factor of 1.6x

However, the old APS-C film format was 25.1 x 16.7 mm (crop factor
1.4x, while the sensor in Canon EOS 400D's sensor is 22.2 x 14.8 mm
(as you say: crop factor 1.6x), so, while Canon's marketing literature
use the term "APS-C" for sensors of this size, it is not really
accurate. See, for example:
http://www.usa.canon.com/consumer/controller?act=ModelTechSpecsSupport...&fcateg

> Then again, the Nikon D40 also has an APS-C sensor, but has a crop
> factor of 1.5x

AFAIK know, Nikon themselves has never described the D40 sensor as
"APS-C" (even if it closer to the true APS-C size than Canon's
sensor). Instead they Nikon prefer to use the term "DX" (which is
new term and not a holdover from the film era) for its 1.5x crop
sensors. The size of the D40 sensor, btw. is 23.6 x 15.8 mm.

> There really is no fixed definition of what size an APS sensor
> actually is,

Yes there is, at least if one believes that the term "APS-C" really
should refer to a sensor the same size as the APS-C film frame
(ie. the "classic" form factor frame of the old APS film format).
See: http://en.wikipedia.org/wiki/Advanced_Photo_System

It is just that Canon-droids has confused things by adopting the
film-era term "APS-C" for some arbitrary smaller digital sensor
format.
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://hannemyr.com/photo/ ]
------------------------------------------------------------------------
Sigma SD10, Kodak DCS 14n, Canon Powershot G5, Olympus 2020Z
------------------------------------------------------------------------
 >> Stay informed about: Making sense of the sensor size? 

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"RPS" <rps.RemoveThis@null.void> wrote in message
news:290820071028155958%rps@null.void...
> Could somebody please explain the jargon used to denote the sensor size?
> I mean numbers like 1/1.7. How does this translate to actual size
> (dimensions or area)?

It actually doesn't translate very well at all, and is a goofy system that
should have been abandoned long ago. The fraction refers to the old video
tube size in inches, which is the way such sensors are traditionally sized
but obviously has nothing to do with digital still cameras.

>
> What is the typical size for DSLR?

Those are not described in that way; only compact cameras use the fractional
inch method. Nikon and some other DSLRs mostly use a sensor of either 23.7 x
15.6 mm or 23.6 x 15.8 mm, in either case roughly the same as the full APS-C
format and often referred to by that term. Most Canon DSLRs s have a
slightly smaller sensor than that, some other makes are smaller still, and a
very few are larger.

> For ZLR?
> For good P&S?

Both of those types use sensors in the fractional inch sizes, though often
the "inch" is omitted and "type" is substituted. So for example one
manufacturer may call a particular sensor "2/3 inch" and another may call
the same sensor "2/3 type."

Whatever it's called, the 2/3 type is the largest sensor generally found in
any digicam. Its actual size is about 6 x 8 mm.

Other common sizes are 1/1.8 and 1/2.5 -- there are several other sizes as
well, but those appear to be the ones most often used today. I have read of
sensors as small as 1/3.2 but have never owned a digicam with that small a
sensor myself.

In high-end compact cameras of the type you call ZLRs, such as the Nikon
Coolpix 8800, the 2/3 type was common. Most of today's superzoom ZLRs use
much smaller sensors than that, however.

For a very good but more compact camera such as the Nikon P5000, the 1/1.8
type is used and is undoubtedly the best choice. Smaller sensors than that
are more likely to give problems with noise at the higher ISOs, all else
being equal. But where extreme compactness is important it's usual to see
sensors of 1/2.5 type or smaller. Also, many of the superzooms today use
1/2.5 type sensors. It is adequate for most ordinary use.

Camcorders of course have much smaller sensors than these.

Neil
 >> Stay informed about: Making sense of the sensor size? 

"Neil Harrington" <not.DeleteThis@home.today> wrote in message
news:pKydnXD2Utxn-kXbnZ2dnUVZ_oimnZ2d@comcast.com...

>
> Whatever it's called, the 2/3 type is the largest sensor generally found
> in any digicam. Its actual size is about 6 x 8 mm.

Correction, that should be about 6.6 x 8.8 mm.

>
> Neil
 >> Stay informed about: Making sense of the sensor size? 

Neil Harrington wrote:
>
> Those are not described in that way; only compact cameras use the fractional
> inch method. Nikon and some other DSLRs mostly use a sensor of either 23.7 x
> 15.6 mm or 23.6 x 15.8 mm, in either case roughly the same as the full APS-C
> format and often referred to by that term.
>
> ...
>
> Whatever it's called, the 2/3 type is the largest sensor generally found in
> any digicam. Its actual size is about [6.6] x [8.8] mm.
>
> Other common sizes are 1/1.8 and 1/2.5 -- there are several other sizes as
> well, but those appear to be the ones most often used today.

What are the actual physical dimensions of 1/1.8 and 1/2.5 sensors? Do
DSLR sensors really have more than six times the area of a 2/3 sensor? Wow.

Thanks for the informative article.

--
Dave Sill
 >> Stay informed about: Making sense of the sensor size? 

"Dave Sill" <dave DeleteThis @sill.org> wrote in message
news:13dgts6lobirrb7@corp.supernews.com...
> Neil Harrington wrote:
>>
>> Those are not described in that way; only compact cameras use the
>> fractional inch method. Nikon and some other DSLRs mostly use a sensor of
>> either 23.7 x 15.6 mm or 23.6 x 15.8 mm, in either case roughly the same
>> as the full APS-C format and often referred to by that term.
> >
> > ...
> >
>> Whatever it's called, the 2/3 type is the largest sensor generally found
>> in any digicam. Its actual size is about [6.6] x [8.8] mm.
>>
>> Other common sizes are 1/1.8 and 1/2.5 -- there are several other sizes
>> as well, but those appear to be the ones most often used today.
>
> What are the actual physical dimensions of 1/1.8 and 1/2.5 sensors? Do
> DSLR sensors really have more than six times the area of a 2/3 sensor?
> Wow.

Yep. Compact digicam sensors really are tiny compared to DSLR sensors.

The 1/1.8 type is about 5.32 x 7.18 mm, and the 1/2.5 type is 4.29 x 5.76
mm.

You can find the *approximate* size of any sensor if you know the actual
focal length of the camera's lens and its 35mm equivalence, both best taken
at the long end of the zoom for the sake of better accuracy. Dividing the
latter by the former will give you the digicam's lens factor. Dividing the
diagonal of a full 35mm frame (about 43.2 mm) by the lens factor should give
you the diagonal of the digicam's sensor. However, this is a rough method
(because the camera lens's stated focal length may not be precise) and may
not give you exactly the figures above.

More sensor sizes are given here:
http://www.dpreview.com/learn/?/Glossary/Camera_System/sensor_sizes_01.htm

>
> Thanks for the informative article.

You're very welcome.

Neil
 >> Stay informed about: Making sense of the sensor size? 

"Neil Harrington" <not RemoveThis @home.today> wrote in message
news:LMqdncyWda8cHEXbnZ2dnUVZ_t6onZ2d@comcast.com...
>

>
> The 1/1.8 type is about 5.32 x 7.18 mm, and the 1/2.5 type is 4.29 x
> 5.76 mm.
>
> You can find the *approximate* size of any sensor if you know the actual
> focal length of the camera's lens and its 35mm equivalence, both best
> taken at the long end of the zoom for the sake of better accuracy.
> Dividing the latter by the former will give you the digicam's lens factor.
> Dividing the diagonal of a full 35mm frame (about 43.2 mm) by the lens
> factor should give you the diagonal of the digicam's sensor. However, this
> is a rough method (because the camera lens's stated focal length may not
> be precise) and may not give you exactly the figures above.

Expanding on this a little:

Most (but not all) compact digicams have sensors in the 4 : 3 aspect ratio.
This should be convenient for finding the diagonal of the sensor, since it's
the 3-4-5 right triangle familiar if you remember your geometry, i.e. if one
side is 3 units and the adjacent side is 4, the hypotenuse must be 5.

So in the case of the 2/3 type sensor used in my Coolpix 8800 for example,
the 6.6 x 8.8 mm sensor has a diagonal of just 11 mm. A full 35mm frame (24
x 36 mm) has a diagonal of about 43.2 mm, so the lens factor is 43.2 / 11 =
3.927. . . , and multiplying this by the lens's marked focal length (at the
long end) of 89mm, the 35mm equivalence works out to about 349.5mm. This is
close enough to the stated f.l. of 350mm at the long end. This is really
just doing the same math suggested in my previous post, only backwards.

The aspect ratios are different of course, the full-frame 35 being 3 : 2
while the digicam's is 4 : 3. But this doesn't really matter; it's always
the format diagonal that's used in calculations of 35mm equivalence.

Neil
 >> Stay informed about: Making sense of the sensor size?