With the right lens, perfect photos are at your fingertips. A lens filters and focuses light so that it hits the sensor or film strip correctly. There are a variety of factors that go into determining how exactly the photo will turn out with that specific lens. Things such as focal length, lens aperture, and depth of field all play a part in the specific lens you are using and how the photos will come out. Focal Length is the measurement of distance, in millimeters, between the point of convergence of your lens and the sensor recording the image. The focal length of a lens is expressed by a number, and that number tells you how much your camera will be able to capture. Smaller numbers have a wider angle of view and show more of what you are trying to capture; larger numbers have a smaller angle of view and show less. Aperture is how big the opening is that lets light in, expressed in f-stops. The best way to understand f-stop is the larger the number, the smaller the opening. Lenses will list a maximum aperture on the lens itself, which is the widest a lens aperture can be open. The depth of field helps in controlling the amount of the photo that is in focus. This helps to draw the viewers eye to a certain place. The depth of field varies with the type of lens, due to maximum aperture.
When looking at lenses there are many varying types of them. From prime lenses to telephoto, to standard and everything in between there are many ways to choose the best one for your situation. The two main categories that the other lenses fall under are the Prime lenses and Zoom lenses. Prime lenses have a fixed focal length, making them faster and sharper. Whereas zoom lenses use a series of lenses to allow different focal lengths from a single lens, making them more flexible but not as fast. Under the two of those, you will have macro, telephoto, wide angle, standard, specialty, fisheye, tilt-shift, and infrared lenses.
Most standard DSLR cameras come with a standard lens and a good second lens to have with it is a telephoto lens. A standard lens focal lengths are usually between 35mm and 85mm. They can be used for a variety of different types of photography which is why they are so versatile. While a telephoto lens is a type of zoom lens with multiple focal points. These are great for isolating certain things a good distance away.
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