Click Thumbnails to Enlarge
Lens focal length explained
Techniques
24 October 2007 09:36
Choice of lens dictates how much of a scene you’re able to include in an exposure. This useful information is described in terms of the lens focal length, which tells you its all-important field-of-view.
Understanding how focal length affects your pictures is very useful. The easiest way of thinking about it is to remember that on standard 35mm-film SLRs, the 50mm focal length equates to the stereoscopic view from our eyes (which is why images look so ‘natural’). In DSLR photography, the most natural field-of-view focal length is around 30mm (on a DSLR with an APS-C sized sensor).
Shorter focal lengths (wide-angle lenses) give a wider-angle of view; longer focal lengths (telephoto lenses) give a narrower view. You’ve probably already come across these numbers on the lens that came with your DSLR, which is likely to have a focal length of around 18-55mm. This means you have the option of shooting the image from a wider to a narrower view than your eyes.
In digital photography, telephoto lenses typically have a focal length of 50mm and longer, giving a much narrower field-of-view than those with shorter focal lengths. The higher the focal length the greater magnification the lens will give, allowing you to pick out distant parts of a scene and still fill the frame.
Wide-angle lenses, typically have a focal length of 10mm to 24mm, allowing you to include a broad view. This means you can include more of the width of a scene than with longer focal length lenses, but objects will appear smaller and seem further away.
The standard 30mm focal length gives a similar magnification to our eyes, so can give the most ‘natural’ looking images.