Pick up a lens and you’ll most likely see numbers and letters on the side or front of an optic. Sit and chat with a photographer and they may even use terms and words that seem a little unfamiliar and technical.
But don’t worry, this guide will arm you with all the information you’ll need to understand more about your lenses, how they work and all the technical terms that come with using optics.
Aberration:
Aberration can be the distortion or colour fringing visible within an image and is caused by the limitations of a lens’s design. Typically, more expensive lenses will demonstrate less aberration and elements of these problems can be reduced using image-editing software.
Aperture: Aperture is the space created by lens blades that controls how much light is allowed through an optic. By regulating the amount of light, the photographer can control both the amount of exposure in a scene, but also how much of the scene is in sharp focus. A large aperture (such as f/2. 8) will create a shallow depth of field, while a small aperture (such as f/22) will create a large zone of focus so more of the scene is sharp.
APS-C: Some lenses, such as Canon’s EF-S mount and Nikon’s DX-mount lenses are designed for use with cameras that feature an APS-C sensor. If you’re picking a lens for your camera, make sure it has the right mount or you may have problems such as vignetting or the lens not working properly.
Autofocus: Often referred to as AF, this is the system the camera uses to communicate with the lens and then achieve a focus point so you can capture a sharp image.
Autofocus helps you capture a sharp image at the touch of a shutter button.
Bokeh: Pronounced ‘boh-kay’, this is the name given to the blur created in the areas of the frame that are out of focus. The name comes from the Japanese word boke, which translates to English as blur or haze. Bokeh is more prevalent and obvious when a large aperture (such as f/1. 8) is used and the quality of bokeh will vary depending on the lens you are using and how rounded the aperture blades are.
Coating: More expensive lenses have coatings on the glass to keep out UV light, which can give images a hazy appearance and to reduce the risk of flare while minimising reflections.
Collar: A lens collar enables the optic to be attached directly to a support, such as a tripod or monopod. This is most useful for larger, heavier telephoto zoom and prime lenses when using them to capture wildlife or sports over extended periods of time.
A tripod collar, paired with a monopod, helps lighten the load.
Effective focal length: If your camera isn’t full-frame, it will have a crop factor. Most APS-C cameras have a 1. 5x crop factor (1. 6x for Canon APS-C cameras), while Micro Four-Thirds cameras have a 2x crop factor. The effective focal length of a lens is its regular focal length multiplied by the camera’s crop factor. For example, a 50mm lens on a Nikon APS-C camera has an effective focal length of 75mm.
Micro Four-Third cameras have a 2x crop factor, doubling the focal length of lenses.
Elements: These are the separate parts of glass that are positioned together in ‘groups’ throughout the barrel of a lens. It’s common for a lens to be described as having X amount of Elements in X amount of groups. Lenses with vast focal ranges (70-200mm or 200-500mm for example) tend to have more elements and groups in the lens’ design. Prime lenses can be simpler and have fewer elements, though it’s not always the case.
F-Number: The f-number is a ratio that indicates the aperture settings used with a lens. At one of the scale, an f-number of f/1. 8 will create a shallow depth of field, while at the other end of the scale, an f-number of f/22 will create a large zone of focus.
Fisheye lens: A fisheye lens is an optic with an ultra wide-angle view, typically between 8-12mm. Fisheye lenses get their name from the convex distortion the optic gives to the frame and can be used to capture some creative angles of scenes. There are corrected and uncorrected fisheye optics, with the corrected lens glass trying to keep lines straight.
Fisheye lenses can stretch perspectives for extreme angles.
Filter thread:
The filter thread size is the measurement of the lens’ diameter and common sizes include 46 mm, 49 mm, 52 mm, 55 mm, 58 mm, 62 mm, 67 mm, 72 mm, 77 mm, 82 mm and 86 mm. Your lens has a filter thread so that you can screw in a circular filter, such as a UV or polariser, or even a filter holder that will then take a square-shaped filter.
Check your filter thread size before buying a UV or circular polariser filter.
Focus distance window: The focus distance window is a small scale built into the lens which can be used to judge the distance where the zone of sharp focus will start. This feature can be useful when shooting landscape imagery and will help you keep foreground interest in sharp detail.
Focus ring: An adjustment ring typically found near the front of the lens which allows the photographer to adjust the focus while the lens is set to manual.
Hood: Some lenses come with a lens hood included in the box, others have lens hoods built in. If not, you can usually buy one that will fit your lens on the internet. The job of the lens hood is to shield the front of the lens from the rays of directional light to help reduce the risk of lens flare, which can cause halos and a specular effect on your image.
Image Stabilisation:
Image stabilisation (or optical stabilisation as it’s often called) is a technology that moves the optics during an exposure to compensate for any unintentional movement the photographer makes. This action ‘stabilises’ the lens and reduces the risk of blurred images, particularly during a longer exposure. Image stabilisation is known as IS (Canon), VR (Nikon) and OIS, OSS and VC for other brands.
Kit lens:
These are the optics that are often bundled with entry-level cameras and typically have a focal range of around 18-55mm, making them a versatile optic that can cater for landscapes and portraits. Kit lenses usually have a variable aperture of around f/3. 5-5. 6, which means you can’t get the incredibly shallow depths of field that can be created from a fast lens with a large maximum aperture of f/2. 8 or faster.
Lens types:
L-Glass is the name given to Canon’s range of professional ‘Luxury’ lenses, which can be identified by a red ring around the lens. Sony’s pro line is called G Master and Nikon’s G lenses are pretty hot stuff too.
L-Glass optics feature a red ring around the lens.
Macro: A macro lens is a specialist optic that can be used to capture close-up imager of subjects. This is possible and macro lenses typically have a 1:1 magnification that gives life-size images of subjects. Macro lenses are prime lenses with fast maximum apertures, such as f/2. 8. With long focal lengths, typically 100mm (although you can get 60mm macro optics), macro lenses allow photographers to get close-up shots without spooking their subjects.
Manual Focus:
Photographers can select Manual Focus to bypass the autofocus system. Focus can then be achieved by looking through the viewfinder (or at the LCD during Live View) and turning the lens’ focus ring until the subject become sharp. Some lenses are Manual Focus only meaning they don’t have autofocus.
Prime lens: A prime lens differs from a zoom lens as it has a fixed focal length. Typical focal lengths for prime lenses include 24mm, 35mm, 50mm, 85mm and 105mm. Prime lenses typically have fast maximum apertures, usually f/2. 8, f/1. 8, f/1. 4 or even f/1. 2 for more expensive prime lenses. This enables the photographer to create shallow depths of field and achieve fast shutter speeds in low light.
Prime lenses offer fixed focal lengths and fast apertures.
Push-Pull: A push-pull is a design of zoom lens, which is pretty rare these days. Instead of twisting the zoom ring to adjust the focal length, with a push-pull lens, you literally push and pull to extend the lens barrel and change your focal length.
Teleconverter:
A teleconverter is an accessory that sits between your camera and lens. By moving the lens further away from the camera, this increases the magnification of your lens. Teleconverters typically come in 1. 4x and 2x magnifications but beware, when you add this extra glass, your maximum aperture will be reduced.
Telephoto:
A telephoto lens is a prime or zoom optic with a focal length of 80mm or upwards. The term telezoom is commonly used to talk about telephoto lenses with variable focal lengths like 70-200mm or 70-300mm. Zooms and primes can extend to 800mm and beyond. These lenses magnify the subject, making them suitable for wildlife and sports photography, where it can be difficult to get physically close to your subjects.
USB port:
Some lenses include a USB in their design. This is present so photographers can connect the lens to the computer to either calibrate the optic or update its firmware. Alternatively, some lenses have special docks for the same job.
Vignetting:
A term to describe the darkening of the edges of the frame, which is caused by the lens’s inability to distribute light evenly across the entirety of the glass.
Wide-angle:
A wide-angle lens is an optic with a focal length of anything below 35mm. Many wide-angle lenses these days have a focal length of below 18mm and are referred to as ‘ultra-wide angle’. These lenses give a very wide angle of view and can stretch the perspective of foreground close to the lens, so they’re suitable for photographing subjects such as landscapes or cramped interiors.
Zoom ring:
An adjustment ring, typically found near the front of the lens, which allows the photographer to adjust the focal length of the lens.
. digitalrev.com2018-1-5 03:00
