Camera lenses are available in many sizes.
Explaining camera lenses is fairly simple once you understand a few basic concepts. Most lenses have features that are written as numbers and letters that describe the lens's ability to focus as a zoom, close-up or regular lens. Some numbers indicate features such as fixed or removable lenses and SLR, or single lens reflex, lenses. Each manufacturer is different but most camera lens sizes are described in a similar fashion.
Instructions
1. Consider the focal length in relation to the size of a lens. The focal length determines the lens's angle of view and how much the subject being photographed is magnified. The smaller number means more of the subject can fit in the frame. Lenses sized 21 mm to 35 mm are considered wide angle and are good for landscape photos. Average lenses have a focal length of 35 mm to 70 mm. Between 70 mm and 135 mm is considered a moderate telephoto lens, good for portraits. Sport and wildlife lenses require a true telephoto which range from 135 mm to over 300 mm. Lenses with two numbers, for example an 18-55 mm lens, describes the widest and narrowest angle of view of the lens.
2. Note that additional focus features that are part of the lens size. For example, David Johnson of "PC World" demonstrated how one or two letters can make a big difference in size and cost of lens features. An 70 AF and an 70 AF-S lens were compared. Both are auto-focus, but the AF-S uses a built in motor inside the lens that auto-focuses, which makes the lens about four times more expensive. The AF-S also had the letters VR, which stands for "vibration reduction" and helps stabilize the lens, reducing blur in the photos.
3. Describe the diaphragm for f/stops of lenses. The diaphragm controls the amount of light that is allowed through through the lens. The size of the diaphragm is called the aperture, which is described in fractions, called f/stops, which are adjusted to control the size of opening. The bigger the aperture, the more light is available, and the less light you need to take a good photo. This is important for taking pictures from a distance or for indoor shots.
The higher the f/stop number, the wider the lens opening. The lower the f/stop number, the smaller the diaphragm. Most lenses are expressed as maximum aperture size or the widest the lens will open; for example, you might describe a lens with a maximum aperture of f/3.5 which would be faster than a lens with a maximum aperture of f/5.6.
4. Explain how lower f/stops affect depth of field, which is the range of distance that a subject or photo appears acceptably sharp. F/stops ranging from f/1.4 to f/3.5 give a shallow depth of field because they allow more light to enter the lens and higher f/stops allow less light but give a greater depth of field.
Tags: depth field, focal length, maximum aperture, angle view, aperture which, describe lens