If you're looking into getting your first interchangeable lens camera and are trying to understand why you need different lenses, the images in this article will help you visualize the effective Field of View on most a good range of lenses. I will focusing on only the type of lens and field of view, not the aperture and depth of field factors as that is another article, another science really.
Comparing Different Lens Field of Views Represented by Vertical Angular Spread
Focal length is measured in millimeters (mm) and is written on the barrel of every lens. The measurement in a typical case describes the distance between the front lens element and the camera's sensor. The smaller the mm number, the wider field of view the camera will display.
This camera has smaller sensor than the one the lenses were designed for, known as a full frame sensor. The Sony A6000's sensor is APS-C sized, giving and effective field of view 1.5x that of the reading on the lens. Less than 1/6th of the top 300 interchangeable lens cameras on the market today have Full Frame Sensors, while over half have sensors equivalent to the one is used in this article. To fully understand what field of view a particular lens will look on your camera, research you cameras sensor size, and what size sensor the lens was made for to find the appropriate conversion.
Comparing Different Lens Field of Views Represented by Red Bounding Box
Original Images at each of the Focal Lengths
Prime vs Zooms
Prime lenses are lenses that only have one focal length that will not change. Zoom lenses have a range of focal lengths whereas you starting from the widest angle, you can zoom in to the tightest angle and anywhere in between.
Lenses Used for this Visualization:
Canon FD 28mm f/2.8
Canon FD 50mm f/1.8
Canon FD 135mm f/2.8
Cannon FD 200mm f/2.8 S.S.C
Quantaray 500mm f/8 Reflex Lens
Other digital photography gear used in making this article include the Canon EOS M, Sony A6000, MeFoto Globetrotter Travel Tripod, and Manfrotto MKC3 Tripod. This article was also made possible by Coffee and Gloves, enabling me to conduct this visualization on a beautiful but frigid 25º Manhattan Morning.