When you first start looking at DSLRs, you’ll see many confusing terms about lenses. Terms like focal length and angle of view, zoom and telephoto lens just to name a few. You’ll see numbers like 18-55mm and wonder what they mean as well? If you don’t understand these photography terms, you won’t understand lens basics. We’re going to try to explain some of this terminology in non-technical terms to help you understand DSLR lenses.
There are two types of lenses, prime lenses and zoom lenses. Zoom lenses allow you to either rotate a lens, pull a lens forward and back, or press a button to zoom in on an object. When the object you’re looking at gets larger, that's called zooming in. When it gets smaller, that's called zooming out. A lens with 2 numbers, like an 18-55mm lens, is a zoom lens. The smaller number is the wide end of the zoom range, and the larger number is the telephoto end. A 20mm, 60mm, and 100mm lens are all examples of prime lenses from Beachcamera.com. A prime lens can't zoom in or out. It always has the same view when you look through the lens.
Lenses that allow you to take a photo of a wide area, such an entire room of people, or a mountain range, are called wide-angle lenses. Lenses that let you take photos of subjects far away, like small birds, are called telephoto lenses. These lenses can be prime lenses or zoom lenses.
There are two types of wide-angle lenses. Regular lenses, known as rectilinear wide-angle lenses, and fisheye lenses. Photos taken with fisheye lenses from Beachcamera.com look curved at the edges. Fisheye lenses are wider than regular wide-angle lenses.
Macro lenses allow you to take a photo of a subject very close up. Calling a lens a macro lens doesn't have anything to do with whether it is wide-angle or telephoto. It just means you can get very close to small objects and photograph them. Common macro lenses are the Nikon 60mm, Canon 60mm, and Canon 100mm.
Ok, now we come to a very important part of lens basics - focal length. A focal length is a property of a lens, expressed in millimeters. Wide-angle lenses have small focal lengths, such as 10mm or 20mm. The smaller the number, the wider the lens. Telephoto lenses have large focal lengths such as 200mm or 300mm. If you want to take a photo of a bird really far away, and you had a choice between a 200mm lens and a 300mm lens, you would want the 300mm lens.
Field of view, also known as angle of view, shows how wide a lens is, and is expressed in degrees. A 10mm fisheye lens will have a very wide field of view of 180 degrees. Where a long telephoto lens will have a very narrow field of view of 10 degrees. There are many possible lens choices and all will give you a different and distinct image. Once you understand what each is used for, you’ll be able to select the right lens to capture the vision of the world the way you want to present it.