In the good old days there wasn’t much to know about lens focal lengths. Lenses were classified into telephoto, normal and wide angle depending on the cameras in which they were used. 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 longer the distance, the longer the lens. The longer the lens, the more telephoto it’s considered. The angle of view will be wider for a lens with shorter distance. In the older days the focal length was measured in inches but now it is measured in millimeters.
The standard focal length of a full frame digital sensor is 35mm. 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 have various classifications based on focal length and the field of view they provide. The view provided by a wide angle lens is very high and lenses having focal length lesser that 40mm falls in this category. Lenses having focal length in between 40 to 65mm is considered to a normal lens. The view provided by normal lens is similar to that of a human eye. Telephoto lenses on full-frame cameras usually are lenses longer than 70mm, and they range upwards of 300, 600 and even 1000mm. The longer the telephoto, the narrower the angle of view and the greater the magnifying power it provides. Wild life and sports photographers prefer to use this type of lenses. 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. Some photographers object to this narrowing of the angle of view because they’re used to a lens of a certain focal length producing a certain corresponding angle of view. The sensor has the ability to increase the focal length of a telephoto lens and hence is preferred by several professional photographers. 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 digital wedding photography or a simple amateur photography done for self satisfactions and delitment
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