Camera Lens

The lens is arguably the most important part of your camera. For a beginning photographer, deciding which camera lens to use can be confusing. There is no single lens that works perfectly for every situation. Choosing the right lens for the task often becomes a trade-off between cost, size, weight and image quality.  Knowing how lenses work and what each kind of lens does enables you to be able to choose the one that works best for your situation.  Understanding your camera’s lens will make you a better photographer and give you more creative control over your images.

Terms You Should Know

Before we dive into how your lens works there’s a few terms you should become familiar with.

Aberration – Image blurring, color distortion, or reduced contrast caused when singular points on the image don’t translate to single points on the image after passing through the lens.

Chromatic Aberration
Chromatic Aberration

Aperture – Iris like portion of the lens that determines how much light it lets through. When you look at the front end of your lens barrel, you’ll see a ratio number (1:2.8, 1:2.8-4, 1:3.5-5.6, etc.), which is the maximum aperture of the lens.

Crop factor A difference between your camera’s sensor size and a traditional 35mm film frame, also known as focal length magnification. A smaller sensor size of a camera fills a smaller part of the lens and produces a cropped version of the full image. This results in the lens appearing to have a longer focal length than it really has.

Distortion – when a lens produces curved lines where straight lines should be.  The two most common types of lens distortion are barrel distortion and pincushion distortion.

Lens Distortion
Lens Distortion

Focal length – The distance between your camera’s sensor, and the point of convergence in the lens. Focal length is measured in millimeters and determines the type of lens and what it’s used for. The focal length of a lens is usually displayed on the lens barrel, along with the size of the adapter ring.

Focal point – The point in space where parallel light rays meet after passing through the lens or bouncing off the mirror.

Image stabilization (IS) – Feature that reduces blurring cause by shaking of the camera. IS comes in either Optical image stabilization or digital image stabilization meaning camera software assist in reducing camera shake.

Lens fits/ mounts – These come in bayonet, screw-thread, and friction-lock varieties, and they attach the lens to the camera body and join any electrical connections.

Lens Ratio – Ratio of 1 stop to the maximum aperture setting of the lens.

Lens speed refers to the maximum aperture diameter, or minimum f-number, of a lens.

Zoom – Magnification of an image.  There are two types of zoom. Optical zoom which means the magnification occurs by moving parts within the lens, and digital zoom meaning software processes inside the camera magnify the image.

How lenses work

Camera lenses are made of several pieces of curved glass, or lens elements. These elements refract light and direct it to an image plane on the camera’s digital sensor (or film). The amount of distance the crisscrossing light needs to come together properly on the image plane depends on how the glass in the lens is shaped.

Shapes Camera Lens Elements
Different Shapes of Lens Elements

Today’s lenses are measured in millimeters (mm). A lens mm rating refers to the amount of distance between the lens and the focal point and is known as the FOCAL LENGTH.

Lens Focal Length
Focal Length

Focal length determines the lens type and what your image will look like. A very short focal length will allow a photographer to capture a wider field of view. Long focal lengths will cut the area you’re imaging down to a much smaller window.

The complexity of a lens such as the number of elements, their shape, and degree of curvature depends on several factors. The angle of view, maximum aperture, and intended price point are some of the features that determine the composition of a lens. The goal of a lens manufacturer is to maximize image quality and minimize aberrations, while still using the least number of complex elements.

Composition of a Camera Lens
Composition of a Lens

Different Types of Camera Lenses

Prime Lens – A lens with a fixed focal length and no zoom capabilities. Best for portraits, weddings, and street/documentary photography.

Zoom Lens – A lens with the ability to zoom or vary it’s focal length. Zoom lenses works well for portraits, weddings, and wildlife photography.

Wide Angle Lens – A lens with focal lengths between 17mm and 40mm. Gives you a broad view of the scene before you. Good for interiors, landscapes, architecture, forest photography.

Standard Lens – Lens with a focal length of about 40mm to 60mm. This lens is the closest to what the human eye sees. Works best for portraits, weddings, street/documentary photography.

Telephoto Lens – Lens with a focal length of 70mm and longer. Works best for when you can’t get close to your subject and has the least amount of distortion. This lens is also great for portrait photography, sports, wildlife, and astronomy

Macro Lens – Gives you extreme close-up images and ultra detailed photography (jewelry, nature.)

Fisheye Lens – An ultra wide-angle lens – any lens with a focal length less than 15mm. Give you a 180 degree field of vision. Images look distorted like a fish bowl. Works best for panoramic shots, cityscapes, landscapes, real estate, and abstract photography.

Fisheye Camera Lens View
Fisheye Camera Lens View

Lens Mounts

Understanding lens mounts can be one of the most confusing aspects of learning your way around a camera lens.  Basically speaking, a lens mount is a mechanical and electrical interface between your camera and your lens. Mounting systems provide a secure connection between the lens and the camera as well as allow for electrical communication for proper focusing and exposure controls. Lens mounts are often unique to each camera system which makes lenses and cameras from different manufacturers incompatible with each other. Most lens mounting systems use one of the following 3 connection types.

bayonet style -The lens is attached to the camera body by turning the lens in in the right direction with the camera body, then giving a small twist of 45-90° to lock the lens in place.

bayonet lens mount
Bayonet Style Lens Mount

Thread mounts, or screw mounts – The lens is threaded on to the camera body.

Camera Lens Screw Mount
Lens Screw Mount

Breech-lock mounts – Like bayonet mounts but use a self-contained rotating ring on the lens itself to tighten the lens onto the camera body with friction.

breech lock mount
Breech Lock Mount

There are many differences between mounting systems. Size is the main difference but number of tabs in a specific bayonet can vary from one manufacturer to another as well.  Other variations include differences in the direction the lens is rotated to connect with the camera, the connection of electronic contacts, and a specific flange focal distance (FFD). Flange focal distance is the length from the mounting flange (the edge of the lens mount on the camera body) to the image sensor. This distance varies from manufacturer to manufacturer and is one of the main reasons lenses can’t be interchanged between manufacturers.

Camera lenses and lens mounts may seem complicated at first but experimenting with different lenses will help choosing the proper one become second nature.  Once you’re familiar with what your lens can do you’ll have more creative control of your images.  The result will be higher quality, clearer images, and freedom as a photographer to capture your images the way you want to.


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