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Old September 1st 07, 11:05 AM posted to rec.photo.digital,rec.photo.digital.zlr
Bob Williams
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Posts: 451
Default Making sense of the sensor size?

Ron Hunter wrote:
Neil Harrington wrote:
"RPS" wrote in message
...
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


Wouldn't the whole thing make more sense if manufacturers would just
agree to always state the sensor size in sq. millimeters!!!?


Another useful addition would be to state the pixel pitch of the sensor.
This gives an indication of the ultimate light gathering ability of each
pixel on the sensor.
Small pixel pitch = low signal/noise ratio = high noise level in low
light conditions.
For instance, A 10 MP Canon G7, with a 1/1.8" sensor has a smaller pixel
pitch than, say a 5MP Panasonic FZ 20 with a 1/2.5" sensor.
The Canon Sensor itself is larger but its pixel pitch is smaller than
that of the Panasonic sensor.
Bob Williams