The focal length is the distance between the lens and a sensor, usually stated in millimeters (for example, 50mm). Some lenses have a fixed focal length - those are called Prime lenses. Zoom lenses have a range (for example, 24mm - 70mm) which allows you to change the focal length by zooming in or out.
We call lenses with shorter focal length wide, and lenses with a longer focal length long (or telephoto). Lenses with middle focal length are called normal.
Below are three lenses - wide, normal and long. Click on each one to see how differently they will capture the same scene.
Normal lenses (usually around 50mm for most cameras) have an angle of view and perspective most similar to the human eye. But let's discuss how wide and long lenses affect the image in more detail in the next two sections.Next: Wide Lens go back