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Article 2 of 4 in the Film Vs. Digital Series 

Focal length is measured in millimeters (mm), and is standard across all lenses, digital and film. However, because of the smaller sensor on digital cameras, all lenses have a different “magnification factor” on these cameras when compared with film cameras.

To give an example, using the film SLR as a reference, a 50mm lens on a film camera acts like a 75mm lens when mounted to a Nikon digital SLR (1.5x magnification factor). To further complicate this business, because different digital manufacturers have different size digital sensors, these magnification factors change amongst camera brands. The same 50mm lens would act like an 80mm on a Canon Digital Rebel  (1.6x magnification factor).

Here’s a general reference list for lenses on most digital bodies
(approximately 1.5-1.6x magnification factor):

10mm – Super Wide Angle
14-24mm – Wide Angle
35mm – Normal Angle
50mm-70mm – Moderate Telephoto
80-200mm – Telephoto
200mm and up - Super Telephoto

The best advice here is to check with your camera manufacturer before making a focal length decision and know that it is going to be expensive to achieve a very wide angle on most digital SLR cameras. Some D-SLR cameras, known as “full-frame” do not have any type of crop factor, because the sensor is roughly the same size as one frame of 35mm film.

The Good – A 200mm lens becomes a 320mm lens. Chalk one up for digital!

The Bad – An expensive 24mm wide-angle is now a 38mm normal-angle lens. Scratch that chalk mark.

Read the next article in this series: Apertures and ISO Overview

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