If you’re the owner of a new digital SLR or mirrorless camera with changeable lenses, you can better tailor your photography to your subject by changing lens. Though there’s no photographic rulebook when it comes to focal length and aperture, there are a few best practices to remember.
In the image below, you can see four lenses with different focal lengths (if they look a bit strange, it’s probably because their lens hoods are flipped backwards for storage).
Although it’s not an exact calculation, the equivalent focal length to what the human eye can perceive is about 50mm on a full-frame camera and 27mm on a Nikon APS-C or equivalent sensor. This means that what you can see through a lens at this focal length is approximately what you’d see if you were looking at the scene with a naked eye.
It’s important to remember that the size of the sensor of your camera can make a big difference in actual focal length. Some lenses include “adjusted” focal lengths, but if they don’t, you can use this handy lens multiplication factor calculator from Digified.net.
Wide Angle Lens
A wide-angle lens is basically a “far zoomed out” lens; it can capture more of the scene than the human eye can focus on. A typical wide-angle lens has a focal length of 24-35mm. Ultra-wide-angle lenses, which capture even more of a scene, have very short focal lengths of 24mm or less.