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"Crop Factor" Confusion

Whether you’ve bought, or are thinking of buying a digital SLR camera, you’ve probably heard of people talking about crop factors, focal length multipliers of 35mm equivalents.


This brief tutorial is designed to explain what they are, why they are important, why they aren’t important and what they actually mean to you.


First of all, we need to know a tiny bit about film...  Traditional film, properly known as 135 film, was called 35mm because it’s 35mm tall from sprocket to sprocket.  Each actual frame of film is 36mm wide and 24mm tall.


Then, in the middle of the 1990s, camera makers started producing the first consumer digital cameras.  Examples like the Olympus D-200L had 0.2 megapixels.  Nikon, Epson, Canon, Casio, Agfa, Kodak, HP, Canon, Toshiba, Ricoh, Mavica, Minolta, Fujifilm and Sanyo soon all followed suit and produced cameras from 1996 - 1999 with less than 2 million pixels.


The main reason for what seems now to be such low resolution was quality control during the manufacturing process.  The obvious answer was to make sensors smaller, as smaller sensors would be less likely to contain flaws.  And so, we end up with cameras with sensors smaller than a frame of 135 film.

film35mm D5000_Sensor_Unit