Quesion about Image Sensors

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Tom G - 29 Nov 2006 10:06 GMT

Here are the specs for three image sensors on three different cameras
that I'm looking at. I don't really know what the numbers or CCD
means. Can anyone explain? Which one is the best?

Thanks,

Tom

PowerShot A640
Image Sensor 1/1.8" CCD

PowerShot A710 IS
Image Sensor 1/2.5" CCD

Canon Coolpix P4
1/1.8-inch type CCD (8.31 million total pixels)

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Richard Polhill - 29 Nov 2006 12:00 GMT

> Here are the specs for three image sensors on three different cameras
> that I'm looking at. I don't really know what the numbers or CCD
> means. Can anyone explain? Which one is the best?

> Thanks,

> Tom

> PowerShot A640
> Image Sensor 1/1.8" CCD

> PowerShot A710 IS
> Image Sensor 1/2.5" CCD

> Canon Coolpix P4
> 1/1.8-inch type CCD (8.31 million total pixels)

Well the 1/x" is the size of the sensor expressed in reciprocals of an inch,
which seems, for some reason, to be the convention chosen for small sensors.

1/1.8" = 0.56"
1/2.5" = 0.4"

So you can see the 1/1.8" sensor is 40% bigger, which is usually better, all
else being equal.

Of course there are usually far more factors involved in which camera is
"best" than just the sensor size and pixel count.

CCD (Charge-Coupled Device) is the technology used to capture light in the
sensor. Have a look at http://en.wikipedia.org/wiki/Charge-coupled_device.

Rich

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Paul Furman - 29 Nov 2006 17:53 GMT

>> Here are the specs for three image sensors on three different cameras
>> that I'm looking at. I don't really know what the numbers or CCD
[quoted text clipped - 9 lines]
> 1/1.8" = 0.56"
> 1/2.5" = 0.4"

I believe the measurement also refers to some archaic reference from
video cameras and it's the outside of the image circle, not the width of
the actual sensor.

Here's a list of actual sensor dimensions:
http://www.clarkvision.com/imagedetail/does.pixel.size.matter/
Table 5
Sensor Size (mm)
Type Width Height
1/3.6" 4.00 3.00
1/3.2" 4.54 3.42
1/3" 4.80 3.60
1/2.7" 5.37 4.03
1/2.5" 5.76 4.29
1/2" 6.40 4.80
1/1.8" 7.18 5.32
1/1.7" 7.60 5.70
2/3" 8.80 6.60
1" 12.80 9.60
4/3" 18.00 13.50
APS C 23.70 15.70 (also called 1.8")
35 mm film 36.00 24.00

> So you can see the 1/1.8" sensor is 40% bigger, which is usually better,
> all else being equal.
[quoted text clipped - 5 lines]
> the sensor. Have a look at
> http://en.wikipedia.org/wiki/Charge-coupled_device.

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Hemingway - 29 Nov 2006 19:55 GMT

>>> Here are the specs for three image sensors on three different cameras
>>> that I'm looking at. I don't really know what the numbers or CCD
[quoted text clipped - 42 lines]
>> the sensor. Have a look at
>> http://en.wikipedia.org/wiki/Charge-coupled_device.

Why isn't it expressed in millmeters as e.g. for 24 x 36 mm negatives?

Michel

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Paul Furman - 29 Nov 2006 21:00 GMT

> Paul Furman a écrit
>>
[quoted text clipped - 22 lines]
>
> Why isn't it expressed in millmeters as e.g. for 24 x 36 mm negatives?

Like I said, it refers to some archaic reference from video cameras.
Presumably American TV cameras I'd guess. That's where sensors were
first widely used.

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