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What Is a Camera Lens?
A lens is the tool used to bring light to a fixed focal point. For a camera, the lens sends the light to the film strip or to the digital sensor. Camera lenses are made up of a series of glass plates that are spherical convex (thick, bulging outwards) or concave (carved inward).
What Factors Determine How a Camera Takes a Photo?
At its core, a lens filters and focuses light so that it hits the sensor or film strip correctly. However, a variety of other factors determine exactly how the final photo turns out.
- Focal length is the measurement of distance (in millimeters) between the point of convergence of your lens and the sensor recording the image. The focal length of a lens is expressed by a number, and that number tells you how much of the scene your camera will be able to capture. Smaller numbers have a wider angle of view and show more of the scene; larger numbers have a narrower angle of view and show less.
- Aperture is how big the opening is that lets light in, expressed in f-stops. F-stops are counterintuitive, because the larger the number, the smaller the opening. For example, f/2.8 allows twice as much light into the camera as f4, and 16 times as much light as f11. Aperture affects the depth of field: larger openings create a shallower depth of field, while smaller openings make more of the image in focus.
- Maximum Aperture. Lenses will list a maximum aperture on the lens itself, which is the widest a lens aperture can be open. Typically lenses with a wider maximum aperture cost a bit more. A lens with a wide maximum aperture is great for low light situations, so if you are considering night photography, it might be worth the investment.
- Depth of Field. Controlling the amount of the photo that is in focus is one of the photographer’s best tools to help draw the viewer’s eye where you want it. For example, landscapes are typically shot so that everything is in focus, so photographers will shoot at small apertures (e.g. f11 or f16). The depth of field varies with the type of lens, due to maximum aperture.
Six Types of Basic Camera Lenses
There are two basic categories of lenses:
- Prime lenses. Primes have a fixed focal length, making them faster and sharper. Prime lenses are less flexible due to the fixed focal length. Their advantage lays in their speed and weight—you can travel easily with them.
- Zoom lenses. Zooms use a series of lenses to allow different focal lengths from a single lens, making them more flexible but not as fast. They have more glass inside of them, which aides in their flexibility, but they also tend to be heavier and bigger than prime lenses.
Within both prime and zoom types of lenses, there are a variety of lenses all with different focal lengths.
- Macro lenses are used to create close-up, macro photographs. They have a unique construction that allows them to produce sharp images at extremely close range. These lenses are great for nature photography; macro lenses allow you to capture an enormous amount of detail in one image.
- Telephoto lenses are a type of zoom lens with multiple focal points. These types of lenses are great for isolating a subject that is far away, however such great magnification comes at a price for a narrower field of view. In the same way that you would use a telescope to look at stars and planets, a telephoto lens is used for focusing in on distant objects. Many sports photographers use telephoto lenses to provide a sense of intimacy with the subjects on the field (the players) while they (the photographer) are standing on the sidelines or in the bleachers. There are a large variety of different types of telephoto lenses and some can be quite large, heavy, and expensive so take some time in choosing the right telephoto lens.
- Wide angle lenses are great for capturing a lot of the scene into your frame. This is especially useful for landscape photography or street photography. With wide angle lenses, almost everything is in focus unless your subject is very close to the lens.
- Standard lens focal lengths fall somewhere in the middle, usually between 35mm and 85mm. They can be used for a variety of different types of photography. A zoom lens within this range will have a small enough focal length at the bottom end to take a wider angle, full frame photo, and a large enough focal length at the top end to zoom in on subjects.
- Specialty lenses. There are a few other kinds of specialty lenses to consider if you want a unique look to your photographs.
- Fish eye lens. A fish eye lens is an ultra-wide-angle lens that can take in a full 180 degree radius around it. It is named “fish eye” because of the distortion of the image’s field of view that makes even a room in a house look like a bubble.
- Tilt shift lens. A tilt shift lens distorts perspective, making things look smaller than they really are—almost as if they are toys.
- Infrared lens. These lenses play with light rather than perspective, filtering out all light waves except infrared for a unique visual effect.
Different Lens Sizes and Specs
- Angle of view: Very wide
- Description: Very wide view of the world. Great for landscape photography.
- Depth of field: Everything is in focus. Impossible to have a shallow depth of field.
- Distortion of space: Makes things seem farther away than they actually are. Exaggerates the size of anything very close to the camera.
- Angle of view: Wide
- Description: Roughly what a cell phone would capture. Great for street photography.
- Depth of field: Pretty much everything is in focus unless your subject is very close to the camera.
- Distortion of space: Less spatial distortion than a very wide lens, but it still makes things seem farther away than they actually are.
- Angle of view: Normal
- Description: Roughly the way the human eye sees the world. Good for just about any type of photography.
- Depth of field: Easy to have a shallow or deep depth of field, depending on aperture.
- Distortion of space: Very little or none.
- Angle of view: Medium telephoto
- Description: Great for isolating a subject from the background. Good for portrait photography.
- Depth of field: Easy to get a shallow depth of field.
- Distortion of space: Makes things seem closer than they actually are.
- Angle of view: Telephoto
- Description: Ideal for picking out a distant subject, the way a telescope does. Good for compressing your subject and the background.
- Depth of field: Quite often has a shallow depth of field unless everything you’re shooting is quite far away.
- Distortion of space: Makes things seem significantly closer than they actually are.
What to Consider When Investing in a Camera Lens
There are a few important factors to take into personal consideration when investing in a new camera lens.
- Cost. Lenses can get very expensive very quickly, so if cost is an issue for you then consider a middle length zoom lens, for example a 24-70mm (f/2.8) lens. This is a workhorse lens that is great in a variety of situations, from portraits to landscapes.
- Size and weight. Another major thing to consider when buying a lens is the size and how much it weighs. A large telephoto lens can weigh around 10 pounds. Take into account what the purpose of your camera and lens is; if it’s simply to take vacation photos, opt for a smaller, more compact one. But if you’re a, say, travel or wildlife photographer, then a telephoto is important for capturing those rare shots from afar.
- Compatibility. One more thing to think about is whether the lens is compatible with your digital camera. Some lenses don’t work with all cameras, for example a Nikon lens will not work well with a Canon or Sony camera, unless you have an adapter (and even then, not all features work). The lens manufacturer will list what camera bodies the lense is compatible with, so be sure to check.