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Sensor Sizes

By Vincent Bockaert


Typical sensor size of 3, 4, and 5 megapixel digital compact cameras	Typical sensor size of 6 megapixel digital SLRs

This diagram shows the typical sensor sizes compared to 35mm film. The sensor sizes of digital SLRs are typically 40% to 100% of the surface of 35mm film. Digital compact cameras have substantially smaller sensors offering a similar number of pixels. As a consequence, the pixels are much smaller, which is a key reason for the image quality difference, especially in terms of noise and dynamic range.

Sensor Type Designation

Sensors are often referred to with a "type" designation using imperial fractions such as 1/1.8" or 2/3" which are larger than the actual sensor diameters. The type designation 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.

Common Image Sensor Sizes

In the table below "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 converted to millimeters), "Diagonal / Width / Height" are the dimensions of the sensors image producing area.

			Sensor (mm)
Type	Aspect Ratio	Dia. (mm)	Diagonal	Width	Height
1/3.6"	4:3	7.056	5.000	4.000	3.000
1/3.2"	4:3	7.938	5.680	4.536	3.416
1/3"	4:3	8.467	6.000	4.800	3.600
1/2.7"	4:3	9.407	6.721	5.371	4.035
1/2.5"	4:3	10.160	7.182	5.760	4.290
1/2.3"	4:3	11.044	7.70	6.16	4.62
1/2"	4:3	12.700	8.000	6.400	4.800
1/1.8"	4:3	14.111	8.933	7.176	5.319
1/1.7"	4:3	14.941	9.500	7.600	5.700
2/3"	4:3	16.933	11.000	8.800	6.600
1"	4:3	25.400	16.000	12.800	9.600
4/3"	4:3	33.867	22.500	18.000	13.500
1.8" (*)	3:2	45.720	28.400	23.700	15.700
35 mm film	3:2	n/a	43.300	36.000	24.000

(*) Also called "APS-C". Many variants exist. APS-C film measures 25.1 x 16.7 mm, Sony's APS-C measures 21.5 x 14.4 mm, Nikon "DX" sensors measure 23.7 x 15.7 mm, while Canon has several (smaller and larger) variants, e.g. 22.2 x 14.8 mm and 28.7 x 19.1 mm.

Implementation Examples

Below is a list of a few digital cameras (as examples) and their sensor size.

Camera	Sensor Type	Pixel count	Sensor size
Konika Minolta DiMAGE Xg	1/2.7" CCD	3.3 million	5.3 x 4.0 mm
PowerShot S500	1/1.8" CCD	5.0 million	7.2 x 5.3 mm
Nikon Coolpix 8800	2/3" CCD	8.0 million	8.8 x 6.6 mm
Olympus C-8080 Wide Zoom	2/3" CCD	8.0 million	8.8 x 6.6 mm
Sony DSC-828	2/3" CCD	8.0 million	8.8 x 6.6 mm
Konica Minolta Dimage A2	2/3" CCD	8.0 million	8.8 x 6.6 mm

Nikon D70s	CCD	6.1 million	23.7 x 15.7 mm
Nikon D2X	CMOS	12.2 million	23.7 x 15.7 mm
Kodak DSC-14n	CMOS	13.8 million	36 x 24 mm
Canon EOS-1Ds Mark II	CMOS	16.6 million	36 x 24 mm

See also Sensors, Effective Pixels, Pixels, and Pixel Quality.

This article is written by Vincent Bockaert,
author of The 123 of digital imaging Interactive Learning Suite
Click here to visit 123di.com