Understanding Focal Length

55 mm 

ISO - 800

f/ 5.6

shutter speed - 1/20

 35 mm

ISO - 800

f/ 4.5

shutter speed - 1/30

24 mm

ISO - 800

f/4.0

shutter speed - 1/50

18 mm

ISO - 800

f/ 3.5

shutter speed - 1/60

Focal Lengths are represented in millimeters and is the calculation of a distance from where light covers the image in your frame. It tells us all about the view of the angle, along with how much will be captured. The longer the focal length, the narrower the view and higher magnification. Then the shorter the focal length, the wider the view and lower magnification. There is a zoom lens and a prime lens and the difference is very simple. 

Zoom lenses are able to change and is versatility. Now prime lenses are where the focal length is stationary. Many photographers use prime lenses because it has better quality, but you have to shoot at the same length every time. You can get a prime lens with different f/stops though. They also tend to have larger apertures. Prime lenses are great for portraits, since they give off a softer, blurred background. 

The lens is the key factor in photography and different lenses are better for different scenario. A macro lens is best for nature, while a super telephoto lens is good for wildlife and sports. A telephoto lens is also good for wildlife, but is good for portraits too. Then a standard lens is best for low lights and a shallow depth of field. The last is wide-angle lenses, which are made for interiors and landscapes.