A Beginner’s Guide To Focal Lengths And How They Affect Photographs
In the good old days there wasn’t much to know about lens focal lengths. A 100mm lens was a 100mm lens; the only thing you needed to know was whether that lens was a telephoto (as it would be on a 35mm film camera), a normal lens (like on a medium-format camera) or a wide angle (as it would be on a 4×5 view camera). Most people quickly learned what the focal lengths represented for their particular camera format. But these days, with so many digital camera sensor sizes and other lens peculiarities, the millimeter measurement of a lens’ focal length tells only part of the story. Many other factors go into determining the effects a particular lens will produce—from magnification factor to zoom range and much more.
The distance from the center of a lens to the image in focus is considered to be the focal length of a lens. The length of the lens will increase with the distance. A longer is lens is considered as a telephoto lens. The shorter that distance, the wider the angle of view. The most common measurement of lens focal lengths is in millimeters, although some old-school photographers still refer to large format lenses in inches.
A full-frame digital sensor is equivalent in size to a 35mm film frame; making this the standard focal length baseline that today’s lenses are measured against. A 10mm wide angle is considered to be short focal length and a 17mm lens can be taken instead of a 28mm or 35mm lens.
Lenses are classified based on the field of view and the focal length. A wide-angle lens provides a much greater field of view, and is generally considered to be any lens 40mm or shorter (again, in full frame equivalent terms). A normal lens—on a full frame DSLR—is the distinction given to any lens that ranges roughly from 40mm to 65mm or so. These lenses are “normal” because they provide an angle of view that approximates that of the human eye. Lenses with focal length 70mm to 1000mm are considered as telephoto lenses and generally used in full frame cameras. The longer the telephoto, the narrower the angle of view and the greater the magnifying power it provides. That’s why wildlife and sports photographers so often use 600mm and longer telephotos. Most amateur users, though, tend to top out around 300mm lenses for most uses.
A smaller sensor will have an effect over a lens of given focal length called the crop factor or magnification factor. A small sensor has the capability of producing a magnification of the images. This type of effect on the lens using sensors is not preferred by some photographers because they like to stick on to a certain focal length lenses. Other photographers actually prefer a crop factor because it has the effect of making a long telephoto lens behave like an even longer telephoto lens. A 400mm lens will have the effect of a 600mm lens when combined with a sensor of 1.5 magnification.
Thus, if you want to become a photographer, it is essential for you to learn all these tips and especially the focal length concept to give a sharp edge to your photography business be it wedding photography tricks or a simple amateur photography done for self satisfactions and delitment
July 8, 2011
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Posted by Jam Man
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