Are focal lengths equivalent on film and digital cameras?
Take a look at the lens on your digital camera. You will probably see the focal length measurement (in millimeters) there, defining whether the lens is wide angle, telephoto, or normal. For instance, you might have a Casio QV-3000EX digital camera with a 7-to-21-mm zoom lens. But take a look at Casio’s documentation and you’ll see that the lens focal length is also listed as 33 mm to 100 mm. The latter figures refer to the equivalent wide-angle-to-telephoto coverage of a lens on a 35 mm film camera. Same thing, right? Wrong. Digital camera lenses have significantly shorter focal lengths because the CCD (or charge-coupled device, the light-sensitive semiconductor chip that captures the image) is physically smaller than a frame of 35 mm film and, therefore, doesn’t need all that extra glass. While the amount of coverage (how much of a scene is captured) may be the same, the laws of optics say that the shorter focal length lens will always have greater depth of field (the area in which th
