The beautiful construct of optical wonderment that is your camera lens, is something that many of us sometimes take for granted. We wipe our precious glass with our shirts or hurriedly toss them into our camera bags as we contort ourselves during on the go lens changes. Indeed, our lenses are the very gateway into the soul of our photography. But how much do we really know about our lenses?
It’s true, some of you know quite a bit about lenses, bravo to you! But there are still others who are just starting out who need a little help to decipher all the terms and confusions that come along when wading through the murky world of camera lenses.
This article will give you a helping hand by offering some general information to aid you in making sense of some things you might encounter involving camera lenses. If you are a complete beginner struggling to make sense of all those numbers on the front of your lens this will be somewhat of a “Lenses 101” lesson and great starting point. If you’re a seasoned shooter, then maybe the information here will be a nifty little refresher course. Either way, you’ve came to the right place!
Basic Lens Anatomy
Lenses occupy a space of wonderful duality. They are simple constructions with an a array of glass pieces, arranged in a specific order, to allow light to pass from one end to the other and ultimately into your camera. At the same time, camera lenses are EXTREMELY complicated pieces of optical engineering that would be considered conduits of magical endows (remember the trouble Galileo got into?). Still, all camera lenses share some basic components. Here are some the major parts you need to understand
Lens Barrel
The the actual tube shaped housing which holds all the guts of the lens is called the lens barrel or lens body. It can be manufactured from a wide variety of materials ranging from plastic to metals. Generally the construction of the lens barrel determines the sturdiness of the lens and its resistance to the elements
Lens Elements
Housed within the barrel are the lens elements. These are the optical framework of the lens which focus and direct light entering the front of the lens into the camera. They are virtually always made from glass of varying quality. The configuration of the elements determine the focal range of the lens, and thus, the image producing capabilities of the lens itself.
Bayonet
The end of the lens which attaches to the camera body is called the bayonet (or mount). The lens bayonet is made to fit specific types and brands of cameras. Think of the bayonet as the key, and the camera as a lock.
Zoom Ring
A zoom ring is what you turn to either zoom in or out with your lens. It is part of the lens barrel itself and varies in appearance. The zoom ring is present on zoom lenses only.
Focus Ring
Virtually all camera lenses (those on interchangeable lens cameras like DSLRs and mirrorless cameras) have a ring can can be used to manually adjust the focus of the lens. Focus rings are present on autofocus and fully manual focus lenses alike. Unlike the zoom ring, the focus ring only affects the focusing distance of the image and not the focal length. The focus ring is usually located to the immediate front or rear of the zoom ring on lens barrel.
Aperture Ring
Found on many older fully manual lenses, the aperture ring controls the size of the opening within the lens depending on the “f-stop” you select. The aperture ring is commonly located on the lens barrel close to the bayonet.
Aperture Blades
Aperture blades are located inside the lens and control the size of the opening (aperture) through which light enters the camera. The aperture blades are controlled either electronically by selections made on the camera or manually by the photographer using the aperture ring on the lens barrel.
Other Terms You May Encounter
Focal Length
This is a term which can honestly be as complicated or as simple as you choose to make it. Physically, the focal length is the distance between your camera’s image receptor (digital sensor or film) and the point where the light entering the lens converges making the image appear in focus (usually in the centre of the lens barrel). This distance is usually measured in millimetres such as 50mm, 200mm, etc.
As the focal length increases so does the zoom of the lens. This is why wide angle lenses are referred to as short focal lengths, and telephoto lenses are referred to as “long focal lengths”.
Lens Speed
The term speed is encountered with a few aspects of photography. As it relates to lenses, speed refers to the maximum size of the aperture possible with a particular lens. This translates into how well the lens performs in low light situations. A lens with a maximum aperture of f/2.8 is considered “faster” than a lens with a maximum aperture of f/4 and so on. Because f/2.8 is a larger opening than f/4, that consequently allows you to shoot with a faster shutter speed – this is how that term is derived.
Lens Distortion
Lens distortion is just that, distortion of the photo due to the nature of the lens elements. Generally, the shorter the focal length of a lens the more distortion is encountered. Images seem to bulge and the perceived size of objects within the lens are skewed.
Chromatic Aberration
This a term you will encounter when reading many lens reviews. Chromatic aberration is an optical phenomena where multi-color fringes appear on the edges of objects within a scene (usually on the edge of the frame). Usually aberration occurs when objects are highly contrasted within a photo. It is caused by the lens not accurately focusing all three colors (red, green and blue) at the same point, and is most often experienced with kit lenses or those less expensive.
Coma
This is another optical manifestation inherent in many lenses due to the shape and minute misalignment of the lens elements themselves. Coma is the distortion of fine points of light within an image making them appear to be elongated. If you plan on shooting a lot of night skies and stars, the amount of coma produced by a lens should be at a minimum.
Bokeh
Derived from the Japanese word “boke” which means blur or haze, bokeh describes the amount and characteristics of background blur produced by a camera lens. Bokeh is often very important to portrait photographers when shooting at very wide apertures.
Two Main Types of Camera Lenses
Prime Lenses
Lenses which do not zoom in and out and use only a fixed focal length are said to be “prime”. Prime lenses generally have fewer lens elements and are therefore usually smaller than zooms. At times, avoided due to their fixed focal range, prime lenses are finding use with even hobbyist photographers (never left really) due to their arguably superior performance in terms of sharpness and speed in relation to cost.
Zoom Lenses
Lenses which are capable of operating at more than one focal length are referred to as zoom lenses. This is facilitated by moving the lens elements closer or further apart inside the lens barrel by means of the zoom ring. The added flexibility of variable focal length, however, often means that zoom lenses are larger and heavier than prime lenses.
Making Sense of the Numbers
F-Stops
There is so much misunderstanding and confusion when it comes to f-stops because it’s a tedious and somewhat complicated concept. At its simplest, the term f-stop is merely a ratio between the size of the opening in a lens and the focal length.
For our purpose, f-stops are related to the lens speed. On most lenses, the aperture range of the lens is stated in f-stops such as f/3.5-5.6 or f/2.8. The thing to remember is that f-stops work counter to common logic meaning that the lower the f-number the LARGER the maximum opening size of the lens.
Filter Sizes
Filters are common photography gear and most lens have threads on the front of the barrel to accept different types of filters. However, lenses have varying diameters and therefore each requires a specific size filter. The filter size of a lens is measured in millimetres and will generally be printed on the front of most lenses designated with a “Ø” followed by the size (you can also find inside the back of your lens cap). The filter size also is helpful when locating replacement lens caps.
In the end
As with all things, knowledge is power. The more you know, the more likely you are to make better decisions that will in turn produce better outcomes for your photography. Understanding the basics of camera lenses and their common terminology will go a long way to help you be the best photo maker you can be.
If you have any other questions about lenses, please ask in the comments section below.
