Sensor Sizes

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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