Magnification Factor for 35mm Lenses

If you are migrating from film and want to use your old lenses on a new digital body, you should be aware that film lenses mounted on most digital camera bodies will magnify images by a factor of 1.5. A 200mm lens on a digital body will to have the reach of a 300mm lens on a film body. Even as you shop for new lenses, you will need to keep this in mind. The reason for this is the size of the sensor that records the image: the digital film, as it were. On most digital SLRs, the sensor is about 2/3 the size of a piece of 35mm film, and the same size as a piece of APS film. The exceptions to this are the most expensive digital bodies, which have 24mm x 36mm sensors. All digital bodies currently selling for less than $1,000 use APS-sized sensors.

The magnification factor is a great boon, of course, if you do a lot of telephoto shooting but if you shoot interiors, or in cities, it is a disaster. Your old 24-70mm zoom, which might have served you well for most purposes, now covers the range of a 35-105mm in film terms. To get any kind of wide-angle coverage, you need to go down at least to 17mm or, better still, 12mm. These very wide lenses have two problems: they are quite expensive, as much as $1,000 for Nikon’s 12-24mm zoom, and they are specially designed for the APS-size, or DX camera bodies. They are not recommended for cameras with film-sized sensors, or for film cameras, and in some cases, won’t work at all on these bodies. However, Nikon’s newest wide angle lens, its 14-24mm f/2.8, is designed for full-frame sensors like the one on its D3 camera, and well suited, for example, to interior photography. It is a professional lens and quite expensive, currently about $1,600.

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