ABSTRACT
Every lens has a maximum aperture, which is the largest possible opening for the lens. It’s often f/2.8, f/3.5, or f/4. The maximum aperture is listed on the lens among the string of letters and numbers that make up the name of the lens. The 12-24 mm lens is listed as “AFS DX Zoom Nikkor 12-24 mm f/4G IF-ED.” Near the end of that lengthy name you see f/4, telling you the maximum aperture is f/4. Some zoom lenses will have a hyphenated aperture such as f/3.5-5.6. This is called a variable aperture. It means that at the wide end of the zoom range the maximum aperture will be f/3.5, but when you zoom to the longest focal length the max aperture will be f/5.6. Nikon’s 18-135 mm lens has a variable aperture of f/3.5-5.6. At 18 mm the maximum aperture is f/3.5, but when you zoom to 135 mm it becomes f/5.6. In between 18 and 135 mm the aperture gradually shifts from f/3.5 to f/5.6. You don’t need to use a lens any differently because it’s a variable aperture lens. Lenses that are variable aperture are smaller and lighter weight than a comparable lens with a fixed maximum aperture.
