A-mount (Sony)The lens mount used by Sony's Alpha SLT cameras. Because these cameras have a mirror in the body, even though it's a non-moving one, the rear of the lens is further from the sensor, so Alpha mount lenses are physically different to Sony's E-mount lens range. You can use Alpha lenses on an E-mount camera with a lens adaptor, but not the other way round.
AA batteriesAA batteries are used rarely in digital cameras (except in some cheap point and shoot models) but used extensively in external flashguns and battery grips. Alkaline AAs will do in an emergency, but rechargeable NiMH batteries are more cost effective and last longer between charges.
AberrationsThese are optical flaws produced by camera lenses and which are largely unavoidable except in the most expensive or the simplest lens designs. They include distortion, chromatic aberration (colour fringing), vignetting (corner shading) and edge softness.
Accessory shoeThis is the technically more accurate name for a camera's 'hotshoe'. These days, they're used for more than just attaching a flashgun, and may be used for external microphones, video lights or electronic viewfinders.
ACROS (Fujifilm)Black and white film simulation mode added to newer Fujifilm cameras. It's designed to give richer, more intense tonal rendition than the regular monochrome film simulation.
Action camsA small, simple and largely automated video camera (you can also shoot stills) designed to attach to a helmet, handlebars, surfboard or any other kind of object and provide dramatic first-person video of adventure sports and other activities. Almost all use fixed focal length super-wideangle lenses and shoot full HD video – some can shoot 4K.
Active D-LightingAn exposure mode on some Nikon digital cameras which balances up the exposure in high-contrast scenes. The camera reduces the exposure to make sure it captures bright highlight detail and then processes the image to brighten up dark shadows. It can be applied in different strength settings.
Adobe RGBThis is a professional colour space offered by more advanced cameras and it captures a slightly wider range of colours than the usual sRGB colour space used by most consumer devices. It can be useful if pictures are destined for commercial print production, but it does introduce complications with colour profiles and monitor calibration.
AE-L/AF-L buttonThis stands for AE (auto-exposure) and AF (autofocus) lock. Often it’s useful to fix the exposure settings and focus point ahead of taking a picture and on most cameras you can do this by half-pressing the shutter button, holding it in position, then reframing the picture. By default, the AE-L/AF-L button does the same, locking both the exposure and the focus, but you can also configure this button to lock either the exposure or the focus, not both, so it's more versatile than simply half-pressing the shutter button.
AF (autofocus) pointsAn area on the screen where the camera can check for sharp focus. Typically, the more focus points the better because this gives you more choice about where to focus and usually indicates a faster and more sophisticated focus system.
AF AssistIn dim lighting the camera’s autofocus system may struggle to lock on to your subject, but on some cameras a lamp on the front of the camera will light up in low light and shines a bright, tightly focused beam of light at your subject to help the autofocus system lock on. Not all cameras have or need this kind of focus assistance.
AF coverageDigital cameras use an array of AF points (focus points) to cover different areas of the frame, but they don't necessarily cover all of it. The AF coverage is the percentage of the frame width and height that contains focus points. Wider coverage is a selling point.
AF fine tuneMost cameras use the main sensor for focusing, but digital SLRs have a different system. They use a separate phase detection autofocus sensor which must be precisely aligned with the main sensor for the focus to be accurate. Sometimes this and different lens designs can lead to small misalignments and slight focus errors, so more advanced DSLRs have an autofocus fine tune feature to correct any discrepancies.
Alkaline batteriesAlkaline batteries are the most common form of disposable batteries. They last longer than older zinc oxide batteries but are still not ideal for many photo products as they have limited capacity.
Alpha (Sony)‘Alpha’ is generic name still used by Sony for all its interchangeable lenses, but it also refers to the older Alpha range of SLT cameras. This can be confusing. Sony has made cameras in two types – SLT (single lens translucent) and mirrorless models. Both are Alphas, but the Alpha A9 (mirrorless) and Alpha A99 II (SLT) are entirely different cameras with different lens mounts and lens ranges. Sony’s SLTs use Alpha A-mount lenses, while the mirrorless models use E-mount lenses.
Aluminium (tripods)Cheaper tripods use aluminium legs which keeps costs down but does add to the weight. This isn't usually a problem if you're travelling short distances or working from the back of your car, but if you're taking a travel tripod on a vacation or hiking any great distance, a more expensive carbon fibre tripod will give a better balance between rigidity and weight.
AnalogA term now used to design old-fashioned chemical processes to capture images rather than digital – so you can get ‘analog’ cameras, ‘analog’ films and ‘analog’ image effects which replicate the look of these old processes.
Angle of viewThis is quoted in degrees, and indicates how much of a scene a lens takes in. Wideangle lenses have a wide angle of view, telephoto lenses have a narrow angle of view. Angle of view is directly related to a lens's focal length, though the different 'crop factors' of smaller sensors means that the relationship between angle of view and focal length is different on different-size sensors.
Anti aliasing filterAnother name for the ‘low pass’ filter fitted in front of most camera sensors. It’s designed to prevent digital artefacts such as moiré patterns and colour fringing caused by interaction between fine linear or rectangular patterns in real-world subjects and the camera’s rectangular grid of photosites.
Aperture (lens)This is the adjustable hole in the lens diaphragm that controls how much light passes through the lens and is used to adjust the exposure. Aperture setting values are the same across all cameras and lenses, and here's a part of the series: f/2.8, f/4, f/5.6, f/8, f/11 – though the theoretical aperture range is much wider than any single lens can manage. The maximum aperture – how wide the lens opening can go – is a big selling point because wider apertures let more light through. The lens aperture also has an effect of depth of field, or the near-to-far sharpness in the picture, and the number of aperture blades is a selling point because it affects the way the lens’s ‘bokeh’.
Aperture bladesThe adjustable hole in the lens diaphragm is created by a set of overlapping metal leaves, or ‘blades’. The greater the number of blades, the rounder the hole created and the better the lens’s ‘bokeh’ in out of focus areas. Aperture blades are often curved, too, to enhance that circular shape.
Aperture priority (A) modeThis is an exposure mode on more advanced cameras where you choose the lens aperture yourself and the camera then sets a shutter speed that gives you the correct exposure. This gives you creative control over depth of field, for example, without losing the convenience of automatic exposure.
Apochromatic (APO) lensAn apochromatic (APO) lens is designed to offer improved correction of chromatic aberration and spherical aberration using specialised materials and combinations of lens elements. It’s a selling point for lenses, though only indicates the lens design used and isn’t really a guarantee of good performance on its own.
APS-C sensorThis is the most common sensor size in cameras designed for enthusiasts and experts and it's found in consumer DSLRs, mirrorless compact system cameras and some high-end compacts. APS-C sensors are around half the size of a full-frame sensor or the 35mm negative, and measure approximately 24 x 16mm. They have a crop factor of 1.5x, which means that you have to multiply the lens's focal length by 1.5x to get its effective focal length in 35mm/full frame camera terms.
Arca SwissMany tripod heads come with quick release camera plates, and while some are specific to that tripod maker and tripod, which can be annoying, Arca Swiss plates use a standard design that means they should be interchangeable across tripod brands. It's a good selling point in a tripod head.