Making (some) sense out of sensor sizes
We regularly receive emails from readers confused as to the actual size of sensor used in digital cameras. Sensors (CCD / CMOS) are often refered to with an imperial fraction designation such as 1/1.8" or 2/3", this measurement actually originates back in the 1950's and the time of Vidicon tubes. Those who find the specification sheets for these sensors are then even more confused about the relationship between the fraction and the actual diagonal size of the sensor. Inside you'll find an explanation and a table of common sensor sizes. We'll be adding this information to our glossary for future reference.
It all started way back when...
The 'Type' designation given to toady's CCD sensors is that it harks back to a set of standard sizes given to TV camera tubes in the 50's. These sizes were typically 1/2", 2/3" etc. The size designation does not define the diagonal of the sensor area but rather the outer diameter of the long glass envelope of the tube. Engineers soon discovered that for various reasons the usable area of this imaging plane was approximately two thirds of the designated size. This designation has clearly stuck (although it should have been thrown out long ago). There appears to be no specific mathematical relationship between the diameter of the imaging circle and the sensor size, although it is always roughly two thirds.
(Diagram shown to scale but much larger than in real life)
Common Image Sensor Sizes
Table keywords: "Type" refers to the commonly used type designation for sensors, "Aspect Ratio" refers to the ratio of width to height, "Dia." refers to the diameter of the tube size (this is simply the type covertered to millimeters), "Diagonal / Width / Height" are the dimensions of the sensors image producing area.
|Type||Aspect Ratio||Dia. (mm)||Diagonal||Width||Height|
Below is a list of a few digital cameras (as examples) and their sensor size.
|Camera||Sensor Type||Pixel count||Sensor size|
|Canon PowerShot A100||1/3.2" CCD||1.3 million||4.5 x 3.4 mm|
|Canon PowerShot A200||1/3.2" CCD||2.1 million||4.5 x 3.4 mm|
|Casio QV-8000SX||1/3" CCD||1.3 million||4.8 x 3.6 mm|
|Minolta DiMAGE X||1/2.7" CCD||2.1 million||5.3 x 4.0 mm|
|Minolta DiMAGE Xi||1/2.7" CCD||3.3 million||5.3 x 4.0 mm|
|Nikon Coolpix 950||1/2" CCD||2.1 million||6.4 x 4.8 mm|
|Nikon Coolpix 995||1/1.8" CCD||3.3 million||7.2 x 5.3 mm|
|Nikon Coolpix 4500||1/1.8" CCD||4.1 million||7.2 x 5.3 mm|
|Olympus C-5050 Zoom||1/1.8" CCD||5.2 million||7.2 x 5.3 mm|
|Sony DSC-F717||2/3" CCD||5.2 million||8.8 x 6.6 mm|
|Minolta DiMAGE 7Hi||2/3" CCD||5.2 million||8.8 x 6.6 mm|
|Canon EOS-D30||CMOS||3.2 million||22.7 x 15.1 mm|
|Nikon D1||CCD||2.7 million||23.7 x 15.6 mm|
|Nikon D100||CCD||6.3 million||23.7 x 15.6 mm|
|Canon EOS-1Ds||CMOS||11.4 million||36 x 24 mm|
|Kodak DSC-14n||CMOS||13.8 million||36 x 24 mm|