Digital SLR cameras feature interchangeable lenses that offer different shooting characteristics.
The Nikon D40 is a digital SLR camera used by professional and amateur photographers alike for more high-quality photography compared to a standard point-and-shoot digital camera. Like other SLR cameras, the D40 can be equipped with different lenses that provide different shooting abilities. Lenses feature different focal lengths, shutter speeds and aperture sizes, all of which affect the outcome of your shot. A prepared photographer has a stable of lenses that allow him to shoot in any given situation.
Standard Lens
Standard is a term that is used to refer to lenses that have a focal distance of around 50 mm. These are typically the lenses that are packaged with SLR cameras when you purchase them, such as the Nikkor 18-to-55-mm lens packaged with the D40. These lenses closely replicate the range of the human eye and are often cheap and versatile lenses. If you do not have one of these lenses, it is a good place to start for a well-rounded lens that allows you to shoot in most basic situations.
Fixed Focal Length Lens
Also known as prime lenses, these are lens that have a fixed focal length; i.e., not zoom lenses. These lenses are often of high quality because they are specially designed for one specific focal length rather than a range of focal lengths. They also have the advantage of having a larger aperture diameter, allowing them to capture more light. Having a prime lens on hand allows you to shoot in low-light conditions. Prime lenses can be found with wide-angle focal lengths, telephoto focal lengths and everything in between to cover all shooting situations.
Wide-Angle Lens
Wide-angle lens have a very short focal distance -- under 50 mm -- and allow you to take close-up images of a subject while fitting more of it into the frame. These lenses are useful for landscape shots and other outdoor scenes. They have a deep depth of field, meaning more of the picture is in focus, so you can vary your distance from the subject without worrying about constantly changing the focus. The wider the lens goes, however, the greater the potential for image distortion, such as a fish-eye effect.
Telephoto Lens
The opposite of wide-angle, telephoto lenses have a longer focal length to capture subjects from afar. Medium telephoto lens can have a focal distance between 85 and 135 mm while longer telephoto lenses can go up to 300 mm. These types of lenses are useful for portraits, as they separate the subject from the background. Unlike wide-angle lenses, they have a shallow depth of field, so getting the focus right is very important. Also, the longer the focal length, the greater the impact of camera shake. Using a tripod is important for these lenses.
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