How do Camera Lenses Work?

How do Camera Lenses Work?


Understanding how your camera lens works will go a long way to you being able to take the quality images that you want to take. It will help you decide which lens you should use in different shooting environments leading to a more satisfying result overall for you when taking your photographs.

How are Camera Lenses Measured?

Camera lenses are measured by their focal length which is generally expressed in millimeters. A high number of millimeters will equate to a larger zoom capability and a lower number will mean you can use your camera for wider shots.

How do zoom Lenses Work?

There are two types of zoom, optical and digital, and both of these zooms work in completely different ways. Although both of these zooms are a way to magnify your images and get closer to your subject, they both offer differing results and ultimately the optical zoom will always give you a better image in the end. So how do they work?

Optical Zoom
Basically, the optical zoom on a digital camera is determined by the focal length of the lens, in other words, the length the light has to travel in order for it to get onto the sensor. Zoom lenses contain a number of moveable glass elements. The manner in which you adjust these elements will determine the zoom capacity of your lens.

As this will change the focal length and reduce the field of view, which in effect magnifies the image you are looking to photograph. The determining factor here is that the number of pixels captured remains the same when it is magnified and the only thing that changes between a normal non-zoomed shot and a zoomed shot is the manner in which the light rays are projected onto the sensors to for the image.

Digital Zoom
Unlike optical zoom, digital zoom will scale up the number of pixels in the image after you have taken the shot. In effect, the camera is cropping and resizing your image for you instead of you doing it in post. Because you are increasing pixels and filling in the blanks, you tend to get an image of far less quality than you would using optical zoom.

A lot of the effects that you get using digital zoom you can get on your computer in a post, however those that are not computer savvy or do not own a computer will enjoy the option of digital zoom. Also, some of the smaller compact cameras only offer digital zoom and not optical zoom.

Types of Camera Lenses and Their Uses

There are a number of different lenses and picking the right one to achieve a quality image is important. In order to decide which one is right for you, you need to take into consideration the environment you are going to be shooting in, lighting conditions and the distance you will be shooting at are some of the consideration and no one lens will be perfect for every shooting situation.

Standard lenses
These are the most common type of lens, and if you ask a professional one of the most used lenses as they produce quality images time after time. They will offer you a mid-range focal length.

Macro lenses
These are lenses that are specifically designed to be used when doing close up shooting. Their shape and construction are different from your standard lenses and are designed to offer both sharpness and contrast. Great for taking detailed photographs such as cataloging, shots of insects or plants and any other small objects.

Telephoto lens
These have a long focal length and will give you great magnification. They will allow you to shoot from a far distance or moderate distance but not close up as they do not offer lower focal lengths. They are perfect to use at sporting events and for shooting wildlife.

Wide angled lenses
These types of lenses offer a shorter focal length. They allow you to get an angle of view that is not available on your standard lens. These are great lenses for taking landscape shots as you can include a wider scene into your shot composition. Very wide-angled lenses are called fisheye lenses and can give you up to a 180-degree view.

Speciality lenses
These are not common lenses and are only used for specific types of photographs. You get tilt-shift lenses and perspective control lenses, and then you get those lenses that are meant to be able to offer creative effects when using them.

Kit lenses
These are the standard lenses that are included when you purchase your DSLR camera. They are known as starter lenses and are great for you to learn how to use your camera and lens.

Telephoto lens vs zoom lens
The basic difference between these two type so lenses are their focal length. A zoom lens has a variable focal length where a telephoto lens has a long focal length. A zoom lens can offer you a wide field of images from telephoto range to wide angled shots. So in other words, it can offer both a low focal length and a high focal length. A telephoto lens, on the other hand, is designed only to work in the telephoto range and will not offer you a lower focal length.

Zoom lens
In order to use these types of lenses you will adjust the barrel of your lens to give you either a narrow or wide field, so in other words, you can make your subject look both larger and smaller depending on how you want to shoot it. It is a variable lens that offers you a wide range of options. Zoom lenses can be used for all types of photography and are a lot more versatile than your telephoto lens.

Telephoto lens
These are lenses that are designed to offer you long-range shots. They are not variable and are specific to their task. Usually, your telephoto lens will not offer you anything less than 70mm but can go up a lot higher. Zooming into subjects that are far away is easy using this type of lens and these types of lenses are great for sports photography and wildlife photography where you are not able to get close to your subject to get the perfect shot.


Understanding what each kind of lens offers you will go a long way to you being able to take the perfect shot in varying shooting conditions. Most professional photographers will have more than one type of lens available to them when on a shoot.

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