Everything You Wanted to Know about Lenses

First of all there is no such thing as a perfect lens. If it were, it would have been too heavy to carry around and too expensive. So you must understand what your needs are and choose your lenses accordingly.

The main characteristic of any lens is its focal length, which ranges from really wide angle to telephoto. Also lenses can be zoom or prime ones. A zoom allows to change the focal length from wide to narrow angle. Prime lenses are usually less expensive and have a fixed focal length which means that if you want your subject be bigger in the frame you have to physically move closer to the subject.

Another point for consideration is image stabilization feature. If you do not plan carrying a tripod, a lens with built-in image stabilization (IS) can serve you a good job by reducing micro shaking of your hands. However please note that this technology fights with your own movements. If you are shooting a fast moving object, it will not help to get a sharp image.



For fast moving objects you need a faster shutter speed to freeze your subject. For this and for low light situations you need to use a lens that opens wide and allows more light to hit your camera sensor. It is called aperture and it can be 2.8 or even less. If you compare Canon 70-200 f4 to 70-200 f2.8 you will see that the latter is significantly bigger, heavier and more expensive. Prime lenses' aperture can be as low as 1.4 or 1.2.

Another important point is to pay attention to the material the lens is made of. Some cheap lenses have the plastic mount ring that is attached to the camera and it will not last long if you keep changing lenses. More expensive lenses feel much more solid and partly are made of metal.

Speaking of quality, some lenses come as weather sealed which will enable you to use it under rain for example.

Check the speed of lens focusing as some lenses may focus faster than the others. Every maker has an ultra sound range of lenses which means their motor rotates much faster and thus faster focusing.

For portrait photography bokeh is important. Bokeh is the shape of the blured light in out-of-focus areas of an image. It is affected by the number of lens' aperture blades and their shape.

Lens Focal Length*	Terminology	Typical Photography
Less than 21 mm	Extreme Wide Angle	Architecture
21-35 mm	Wide Angle	Landscape
35-70 mm	Normal	Street & Documentary
70-135 mm	Medium Telephoto	Portraiture
135-300+ mm	Telephoto	Sports, Bird & Wildlife

*Note: Lens focal lengths are for 35 mm equivalent cameras.