Confused by crop factor or mystified by megapixels? Our photographic A-Z has everything you need to know
Welcome to our photographic jargon-buster! Even the most seasoned of photographers can admit that, sometimes, all the technical terms gets a little confusing. That's why we've put together this guide – to give you clear, no-nonsense explanation for the technical terms you're likely to encounter as a photographer.
There's a lot to remember when it comes to digital cameras, and while you don't need to know the ins and outs of exactly how a sensor works, it's useful to have a grounding in the difference between sensor sizes, to take one example. While you can just stick a digital camera on Auto, point it and hope for the best, taking time to understand the fundamental concepts of photography will make it so much easier to capture fantastic images.
We've ordered this guide alphabetically, and cross-referenced terms in places where we feel it's helpful, so you can easily jump up and down the page by clicking on the relevant term.
1/2.3-inch type sensor
This is the smallest type of imaging sensor found in consumer cameras, and is often seen in smartphones and action cameras. There are some slight size variations in this category, with 1/1.7-inch and 1/2.5-inch sensors, among others, but 1/2.3-inch types are the most common. See also: Sensor
1-inch type sensor
A step-up from the types of sensors used in smartphones, 1-inch type sensors are generally used in small-to-medium compact cameras. They offer an advantage in image quality compared to a smartphone without increasing the size or cost of the camera by too severe a degree. For this reason, 1-inch type sensors are particularly popular in travel-oriented compact cameras. See also: Sensor.
The opening of a lens that permits light to reach the sensor, controlled by an adjustable diaphragm. The size of the lens aperture can be varied to control exposure, and is one of the three components of the exposure triangle. Varying aperture is also the key way to control depth of field in an image. See also: F-stop.
Aperture priority mode (A/Av)
A shooting mode in which the user controls the aperture setting, and the camera automates everything else. Useful for adjusting depth of field.
Offering a sensor of significant size without the cost and bulk of full-frame, APS-C cameras are comfortably mid-priced and very popular for this reason. Most camera manufacturers have an APS-C offering, and many beginner cameras have APS-C sensors. See also: Sensor.
Aspect ratio is the relationship between the width and height of an image or video. It's written in number format, like this: 3:2, 1:1, 16:9, with the first number designating width and the second number designating height. So if we knew an image had an aspect ratio of 3:2 and its width was 3,000 pixels, we could infer that its height was 2000 pixels. An aspect ratio of 1:1 means a perfectly square image.
One of the most common aspect ratios you'll encounter in video is 16:9, as this is the aspect ratios for most TV screens and TV broadcast content. Two common aspect ratios in the world of cinema are 1.85:1 and 2.39:1. These are wider than 16:9, which is why you get black bars at the top and bottom of the screen when you watch movies on TV.
Autofocus is the camera's ability to automatically ensure that the subject of a photograph is rendered sharply. Autofocus has evolved considerably since its introduction in the 1970s, and modern cameras feature highly sophisticated autofocus systems that are capable of incredible precision.
Autofocus systems incorporate several focus points in order to be able to focus on subjects in any part of the frame; it's not uncommon for sophisticated cameras to have several hundred focus points.
A shooting mode in which the camera takes over settings control completely, and all functions except the shutter button are automated.
The name for aesthetically pleasing out-of-focus areas in an image with shallow depth of field. Technically, the term refers to the character and shape of the points of light that appear in these areas – ideally, for smooth bokeh, you want them to be nice and round. However, these days the term is used pretty generally to refer to the out-of-focus area as a whole, and it's only real pedants that will correct you on it. See also: Depth of field.
A bridge camera is a specific type of fixed-lens compact camera. Designed to "bridge" the gap between types, bridge cameras have DSLR-style build and handling, but with the affordability and convenience of a compact. Many bridge cameras have superzoom lenses with incredible levels of reach, the trade-off being that they often use significantly smaller sensors than DSLRs. See also: Compact camera.
The number of images a camera can capture in an unbroken sequence before it needs to stop in order to prevent overheating or missed frames. Professional sports cameras will tend to have large shot buffers, and a camera's shot buffer will often differ depending on what file format the user is shooting in (RAW, JPEG or RAW + JPEG).
A shutter speed setting that leaves the shutter open indefinitely, either by holding down the shutter button or by having the user press it once to open and once to close. As most cameras offer maximum shutter speed settings of about 30 seconds, bulb mode allows users who want longer exposures to exceed this limit.
A camera's ability to shoot continuous, consecutive frames without stopping. A camera's burst capability is expressed in frames per second (fps). More advanced cameras will generally be able to shoot more frames per second than beginner models.
A camera with a fixed lens that cannot be changed. Compact cameras come in lots of different configurations and form factors; the term "compact" has nothing to do with size. See our guide to the best compact cameras for more.
Crop factor refers to the different field of view provded by different sensor sizes. If you mount a 50mm lens on a camera with a full-frame sensor, you'll get a different image than you would if you mounted the same lens on an APS-C camera. The image from the APS-C would look more zoomed in, showing a smaller portion of the whole scene. This difference is called the crop factor.
Full-frame sensors record the full area of the image circle projected by the lens; hence the name "full" frame. Crop factors of other sensors are therefore determined by how much of an image they capture compared to full frame. You can use the crop factor of a sensor to calculate how a sensor's size will affect the lens you're using.
- As full frame is the standard by which other sensors are measured, the crop factor of full frame is 1x – i.e. there isn't one. So, a 50mm lens mounted to a full-frame sensor will behave like a 50mm lens.
- An APS-C sensor records a smaller portion of the image circle than full-frame, and it has a crop factor of 1.5x. So, if we mount the same 50mm lens to an APS-C camera, we multiply it by the crop factor of 1.5x, and this tells us that the lens will behave like a 75mm lens.
- A Micro Four Thirds camera with a Four Thirds sensor has a crop factor of 2x. So, this means that same 50mm lens will behave like a 100mm lens. This is a good example of how crop factor is not necessarily a negative; 50mm standard lenses tend to be much more affordable than 100mm telephotos, and this means that MFT users can effectively get a 100mm lens that's smaller and cheaper than you'd expect.
Depth of field
Depth of field refers to the distance between the furthest two points in an image that are both sharp. When an image has a shallow depth of field, you'll see a sharp main subject and a blurred, defocused background. With a large depth of field, much more of the image will be in focus.
Shallow depth of field tends to be commonly used in portraiture and macro, while larger depth of field tends to be used in landscape photography.
Depth of field is generally controlled by varying the aperture of the lens – a larger aperture means a shallower depth of field. However, it can also be controlled by moving closer to a subject for a shorter distance between camera and subject, or by using a camera with a larger sensor.
The diaphragm of a lens is the component that opens and closes. It consists of overlapping metal blades that can open and close to create an opening of different sizes, thereby controlling the aperture or f-number of the lens. See also: Aperture.
Another name for continuous still-image capture. See also: Burst Mode.
DSLR (Digital single-lens reflex camera)
A DSLR is a specific type of interchangeable-lens camera, a successor to the film SLRs of the 20th Century. The acronym stands for "digital single-lens reflex camera", so let's look at what that means.
"Digital" refers to the fact that the camera uses a sensor rather than film.
"Single-lens" is a term from the film era and refers to the fact that the same lens serves both the sensor and the viewfinder (this was in contrast to rangefinder cameras, which have two lenses).
"Reflex" refers to the internal mirror mechanism, which bounces light onto the sensor and into an optical viewfinder. Mirrorless cameras don't have this mechanism, hence the name.
DSLRs tend to be larger than other types of camera, but they're also often ruggedly built and can handle tough shooting conditions. Many photographers prefer a DSLR for its robust handling and the immediacy of its optical viewfinder, and they're still some of the best cameras you can buy today. Our guide to the best DSLRs goes into more detail.
Dynamic range refers to the difference between the darkest and lightest tones in an image. Camera sensors will have a maximum dynamic range they can capture, and if an image exceeds it, then you will start to lose details in either the brightest areas (the highlights) or the darkest areas (the shadows).
Electronic viewfinder (EVF)
An electronic viewfinder is a type of viewfinder found commonly in mirrorless cameras, compacts and bridge cameras. Essentially, it's a tiny screen built inside an eyepiece, designed to replicate the experience of having a real, true-to-life optical viewfinder, bwithout the need for a bulky mirror mechanism.
EVFs have the advantage of showing a more accurate representation of what your final image is going to look like than an optical viewfinder does, because they are literally taking their data from the image sensor. This means you'll be able to see the effect of your settings adjustments in real time.
However, some photographers are less keen on EVFs, as they need to be high-resolution and have a high refresh rate in order to be useful. See also: Optical viewfinder.
Equivalent focal length
When you see lenses referred to as having a "35mm equivalent" or "full-frame equivalent" focal length, this is referring to how the lens behaves with the camera's sensor size.
An APS-C sensor captures a smaller portion of the image circle than full-frame, so images taken using APS-C are effectively zoomed in by 1.5x. This means that if a 24mm lens is mounted to a camera with an APS-C sensor, it will behave like a 36mm lens; its equivalent focal length is 36mm. See also: Crop factor.
Exposure in digital photography is governed by three things: shutter speed (how long the camera shutter is permitted to remain open), aperture (how wide the lens diaphragm is permitted to open) and ISO (the camera's sensitivity to light).
These three factors form the Exposure Triangle, which is one of the first things you'll learn on a photography course. Nailing a correctly exposed image involves balancing these three things, the idea being that if you increase one (e.g. slow down the shutter speed to increase light) in a correctly exposed scene, to maintain that correct exposure, you must compensate by decreasing another (e.g. narrowing the aperture to reduce light).
Used when a camera is in an automatic or semi-automatic exposure mode, exposure compensation allows the user to step in manually and increase or decrease the exposure. This can be for stylistic or artistic purposes, or because the camera is getting the exposure wrong (i.e. if an unusual amount of white in a scene is causing the camera to think conditions are brighter than they actually are).
Exposure value (EV)
Exposure value, or EV, is quite a complex concept, but not one you need to worry about too much. It's essentially a means of combining shutter speed and aperture to express exposure as a single value, and was used in the days of film photography when being able to mentally calculate a correct exposure was essential. The fact that modern digital photographers have metering systems and can vary ISO levels has rendered the EV equation somewhat redundant.
In practical use, you'll see EV expressed as a number from around -6 to +17, with -6 representing an extremely dark scene and +17 being a very bright one. You might see a camera advertised by its ability to autofocus in conditions as dark as -4EV. Also, you might see it used in the context of exposure compensation – if someone tells you to add +1 EV of exposure compensation when shooting a scene, they just mean to overexpose by a stop. See also: Stops.
The measurement for how wide open a lens aperture is. F-numbers can be expressed in any number of ways; you might see them written as f/2.8, f2.8, F2.8 or anything similar. It all means the same thing.
The smaller the F-number, the larger the aperture. So, an F-number setting of f/1.4 is very large, and an aperture setting of f/22 is very narrow.
The technical reason they are written this way is because they are effectively fractions of the lens's focal length. If you're using a 100mm lens, and have the aperture set to f/2, the diameter of the aperture blades when viewed through the front will appear to be 50mm, a.k.a. 1/2 of the total focal length. You don't need to worry about this stuff too much – again, just remember that a low F-number means a large aperture.
An lens with an extremely wide field of view, producing strong visual distortion and a deliberately exaggerated visual effect. Fisheye lenses can capture a field of view as wide as 180 degrees.
Another term for a compact camera.
Represented in millimetres (mm), focal length is a way of expressing the angle of view and the magnification that a lens will capture. A short focal length provides a wide angle of view with very little magnification; a long focal length provides a narrow angle of view and significant magnification.
The technical definition of focal length is that it's the distance between the optical centre of the lens and the camera sensor.
Four Thirds is the sensor size of the Micro Four Thirds system; it's larger than 1-inch type and smaller than APS-C, designed to provide a balance between image quality and camera portability. See also: Micro Four Thirds; Sensor.
Frames per second (FPS)
This is the number of images a camera can continuously capture. See also: Burst mode.
The standard sensor size for professional photographers, full-frame sensors are so named because they are the equivalent size of a frame of 35mm film – this is why the sensor size is also referred to as 35mm.
Cameras with full-frame sensors tend to be larger and bulkier than cameras with smaller imaging sensors, however the image quality they produce is a clear cut above. With greater dynamic range and detail, full-frame sensors have endured as the professional standard for years. See also: Sensor
A histogram is a graph showing the distribution of light and dark tones in an image. The X-axis measures brightness, running from 0% brightness (pitch black) to 100% brightness (pure light). The higher the peak at each point, the more pixels of that brightness there are in an image.
Most digital cameras are capable of displaying a histogram for an image, and some can even overlay it before the shot is taken. This can be a useful way to be sure that you are not losing detail in the highlights or shadows of an image.
Image stabilisation (IS)
A catch-all term for technology designed to reduce camera-shake to allow for the capturing of sharp images in low-light conditions. You might see image stabilisation referred to as Optical Image Stabilisation (OIS), Vibration Reduction (VR), SteadyShot, Shake Reduction (SR) or any number of other names. Fundamentally, it all means the same thing.
Image stabilisation can be in-camera or lens-based, and in many cases, the two types can work in tandem to increase the stabilisation effect. Essentially it works by physically shifting either a lens element or the camera sensor to compensate for movement – if the camera moves one direction, the system moves its element in the opposite. There are also digital modes of image stabilisation, though these will incur a crop on the image.
As it sounds, this simply refers to a camera that can swap lenses. DSLRs and mirrorless cameras are interchangeable-lens cameras, and which lenses can be used on them will depend on their lens mount.
ISO is a setting that controls your camera's sensitivity to light. The acronym refers to the International Standards Organization, and is a descendent of ASA from the film era, which used to be a standard measurement for film sensitivity.
Cameras will have a base ISO setting, often ISO 100, but sometimes lower. This is the lowest ISO setting that the particular camera can use. You'll then have a number of settings options like ISO 200, 400, 800, all the way up to the maximum ISO setting the camera can use, also known as the ISO ceiling.
Every time the ISO value doubles, it adds a stop of exposure, which is why the numbers climb so high: an ISO increase from 12,800 to 25,600 may sound like a lot, but it's actually only adding a single stop of exposure; the equivalent of changing aperture from f/5.6 to f/4.
The higher the ISO setting, the more sensitive the camera will be to light. So why not just use the highest ISO setting all the time? Because lower ISO settings will produce a higher-quality image with less grain and less image noise. Ideally, you want to use the lowest ISO setting possible in any given shooting situation – though you'll always be balancing it with aperture and shutter speed, an arrangement often referred to as the exposure triangle. See also: Exposure; Noise.
JPEG is one of the most common image file formats. The acronym is short for "Joint Photographic Experts Group", and the file format is hugely popular online as JPEGs retain a decent amount of image quality in a file that is compressed enough to be a reasonable size. You can store a lot of JPEGs on a memory card or hard drive before you fill it up.
Digital cameras tend to shoot in JPEG format by default, and in some cheaper cameras, it will be the only option. More sophisticated cameras will have the options to shoot in RAW; see also: RAW format.
Kelvin is the unit of measurement used to determine the white balance of an image. See also: White balance.
This is the screen that is embedded in the back of the vast majority of digital cameras. Short for "Liquid Crystal Display", an LCD screen allows the user to compose images, view previously shot images in playback, and adjust camera settings.
LCD screens have different resolutions, the value of which is generally expressed in "dots". The more dots a screen has, the sharper and clearer it is. For a while, the standard size of an LCD screen was 3 inches, but more sophisticated cameras have introduced larger screens of 3.5 inches or even more.
LCD screens may be fixed in place, or they may be tilting or even fully articulated, allowing the user to shoot with all sorts of unconventional angles. Some camera LCD screens are also touch-sensitive, which can add useful functionality like allowing the user to select focus points via the screen.
The lens mount of an interchangeable-lens camera is the port by which a lens is secured in place. Different cameras can accept different lenses as the mounts are physically different shapes – if a camera is described as "Canon EF" mount, this means it will only take Canon EF lenses, which are also referred to as "Canon EF fit".
It is possible to mix and match some cameras and lenses of different mounts, through the use of mount adapters. However, be aware that this process often comes with drawbacks, such as not being able to use autofocus or image stabilisation, as the camera and lens aren't able to interface with each other to such a sophisticated degree.
Live View is a shooting mode that allows the user to compose via the LCD screen. The screen relays exactly what the sensor is seeing, and can also display readouts of exposure information or a histogram to make it easier to select the correct settings.
Macro is a catch-all term for close-up photography of small subjects. The term "macro lens" technically only applies to lenses that can reproduce a subject on a sensor at life size or greater; this is also referred to as a 1:1 reproduction ratio, and is how you get frame-filling images of minuscule subjects.
These days, however, the term is used more loosely, which is why lenses that do have this 1:1 or greater reproduction ratio are sometimes referred to as "true" macro lenses.
When a photographer controls the focus of a lens by hand in order to render the subject sharply, usually via a manual focus ring on the lens body. Manual focusing can be useful in situations that autofocus systems find challenging, such as low contrast or backlighting. Also, some photographers just prefer it.
Manual mode (M)
Manual mode is a camera setting where the user is fully in control of both aperture and shutter speed, and nothing is automated (ISO control is generally dealt with separately, so a camera in M mode may still be on auto ISO selection if the user has not specified otherwise).
A larger sensor format than even full-frame, based around the size of 120 film. Medium format cameras tend to be slow, bulky and expensive, however the detail they are able to capture is simply unrivalled. See also: Sensor.
Megapixels are the main unit of measurement for camera sensor resolution. A single megapixel is equivalent to one million pixels. See also: Pixel.
Image metadata is textual information embedded in an image file. Digital cameras will imprint certain amounts of metadata in images that can then be read in programs like Photoshop; this can include the make and model of camera, the exposure settings, focal length of the lens, precise date/time the shot was taken, and much more.
Metering is the process of determining the brightness of a scene, and accordingly, what exposure values to use. In the days of film photography this would generally be accomplished via a handheld device called a light meter; modern digital cameras have their own metering systems that power their auto and semi-auto exposure modes.
Metering modes include:
- Matrix/evaluative metering: This is the default metering mode on most cameras, and it analyses the brightness/darkness levels of the entire frame to determine the correct exposure.
- Centre-weighted metering: This metering mode takes its reading from a smaller area in the centre of the image. Useful if you're shooting a portrait and want to ensure the subject's face is correctly exposed.
- Spot metering: Spot metering takes its reading solely from the image's focus point. This can be useful for subejcts that only occupy a small area of the frame.
The system was introduced by Olympus and Panasonic and designed to be completely interchangeable, meaning that Olympus lenses could be used on Panasonic Lumix cameras, and vice versa. Micro Four Thirds is a system with its own lens mount, also known as MFT. See also: Four Thirds.
Mirrorless cameras (also known as compact system cameras) are a type of interchangeable-lens camera. Originally designed as an alternative to bigger and bulkier DSLRs, mirrorless cameras have since come to dominate the world of professional photography, and mirrorless is currently where all the most exciting technological advancements are happening.
Mirrorless cameras are so-named quite simply because they don't have a mirror. DSLRs (and film SLRs before them) use an internal reflex mirror mechanism to bounce light onto the sensor and through an optical viewfinder. Mirrorless cameras don't have this, which allows the bodies to be smaller and lighter. The image from the sensor is passed directly to the LCD screen, or an electronic viewfinder.
The lack of the internal mechanism also makes the cameras more stable, enabling more effective stabilisation systems. They're quieter and faster, with fewer moving parts. You can find out much more in our comprehensive guide to the best mirrorless cameras you can buy.
In photography, noise refers to unwanted image grain that makes an image muddy and lessens sharpness. While there will unavoidbly be small amounts of noise in every photo you take, photographing using higher ISO settings will incur more noise. If a camera is described as having "good high-ISO performance", this means that it can capture images at these settings with relatively little noise.
Optical Image Stabilisation (OIS)
A distinct type of image stabilisation, so-called because it works optically by physically moving elements, rather than digitally. See also: Image stabilisation.
Optical viewfinders allow the user to see what the camera lens is seeing, via a series of mirrors. This is considered to be the main advantage of DSLRs, and the reason that many photographers still prefer this type of camera. While optical viewfinders are obviously immediate, with no lag, they show a smaller portion of the image than what will be included in the final frame.
Pixels are the unit by which we measure a camera's resolution. If a camera has 24 megapixels, it has 24 million pixels, meaning 24 million small squares capable of collecting information to make up an image. Images with more pixels contain more detail, meaning they can be cropped into more easily with no loss of quality, and printed out at larger sizes.
Pixels are not a static size; depending on the physical size of the camera sensor, they may be smaller or larger. 65-million pixels on a smartphone-sized 1/2.3-inch sensor will be individually much smaller than 24-million pixels on a large full-frame camera sensor. The advantage of larger pixels is that they can gather more information – the oft-used analogy is to think of them as a bucket collecting water; you get more water if you use a larger bucket.
Lots of small pixels crammed onto a small sensor can result in an image with lots of unattractive noise and blotchy areas, as the individual pixels are able to gather less light.
A prime lens is a lens with a single, fixed focal length that cannot be changed. If you're using a 35mm lens and want to get a closer view of your subject, your only options are to move closer to the subject, or to change lenses. Prime lenses are much less versatile than zoom lenses, however they generally offer significantly improved optical quality, and many photographers prefer them for this reason. See also: Zoom lens.
Program mode (P)
In Program Mode, the camera selects both the shutter speed and the aperture. This might sound the same as Auto mode, but it's different in the sense that the user can still control ISO, white balance, focus mode, exposure compensation, metering mode and many other functions. In Full Auto, all of those things are camera-controlled.
RAW, also styled as Raw or raw, is an uncompressed image file that records all of the data from the image sensor. RAW files are large, require special software to even view, and restrict the number of burst shots a camera can take before needing to cool off. However, RAW files provide enormous latitude in post-processing; you have so much imaging data that you can radically alter an image post-capture, changing the white balance and even the exposure.
Different camera manufacturers have their own RAW file extensions: Canon uses .CR2, Nikon uses .NEF, and there's also the more common and generic .DNG, as well as plenty of others. Most RAW-processing software will be able to handle any of them, but it's worth double checking before paying for anything.
The term for the number of pixels on a camera's sensor, generally expressed in megapixels (MP). Higher resolution gives you more detail in images, but also means you're working with larger file sizes. See also: Pixel.
The beating heart of a digital camera, the imaging sensor is what records light and ultimately produces an image. Sensors come in different sizes, and the main ones you will encounter in digital photography are as follows (from smallest to largest):
- Four Thirds
- Medium format
Larger sensors confer several advantages. They allow for bigger photosites – effectively bigger pixels that can capture detail more cleanly. This means they can produce sharper images in low-light conditions, with less noise and better detail. They capture a broader dynamic range (difference between the lightest and darkest tones in an image) and improve the quality of background blur.
The trade-off, of course, is that large-sensor cameras tend to come with higher price tags, and necessitate larger camera bodies. As with most things, it's all about weighing up your needs and your budget and deciding what's best for you.
One thing to be aware of with regard to image sensors is that their size can affect the focal length of lenses they're used with; see: Crop Factor.
Shutter priority mode (S/Tv)
A shooting mode in which the user controls the shutter speed and everything else is automated by the camera. Useful if you have to keep to a certain shutter speed for creative or technical purposes; e.g. you need to use 1/500sec to freeze action, or you need to use 1/60sec to keep the image sharp while shooting handheld.
The speed at which the shutter opens and closes, and thereby how much light it allows to reach the sensor. Shutter speed is generally expressed in fractions of a second, like 1/125sec, 1/500sec, 1/60sec and so on, but shutter speeds of multiple seconds and even longer are possible. See also: Exposure.
A lens with a focal length that sits between wide-angle and telephoto, providing a naturalistic perspective that's close to what the human eye sees. 50mm is considered the archetypical focal length for a standard lens, and many beginner cameras come with a standard kit lens with a zoom range of about 18-55mm. See also: Wide-angle lens; Telephoto lens.
A stop is the standard incremental measure of exposure in photography. When we alter a setting like aperture or shutter speed to let in more or less light, we are altering the exposure by a number of stops.
A stop is defined by doubling or halving the amount of light being being captured in an image. If you increase exposure by one stop, you are doubling the amount of light; if you decrease it by one stop, you are halving it. Most digital cameras let you get more granular than this, allowing for the alteration of exposure by 1/3 of a stop.
A telephoto lens is a lens with a long focal length, meaning it magnifies distant subjects and brings them into sharp focus. A lens with a focal length greater than 85mm is generally referred to as a short telephoto, and lenses above 500mm or so are sometimes referred to as super-telephotos.
A tilt-shift lens, also known as a perspective-control lens, is a specialist type of lens that allows its optics to be physically tilted or shifted in order to dramatically alter the plane of focus. The plane of the lens can be altered so it's no longer parallel to the image sensor; what this means in real terms is that you can create images with striking focus effects, playing with perspective to do things like make large objects look extremely small.
See shutter priority mode.
A viewfinder is a small eyepiece that you can look through to preview an image before you shoot. Not all cameras have viewfinders, and different cameras offer different types; see also: Optical viewfinder; Electronic viewfinder (EVF).
White balance refers to the colour of light in an image. There are lots of different light sources in the world and they produce different qualities of light – the light from your bedside lamp looks pretty different from the light of the sun, which looks pretty different from the light of a car headlight.
These lights effectively have different colours, or what is known in photography as the colour temperature. This quality is given a numerical value, which is measured in Kelvin, and runs on a scale from 1,000 to 10,000. Lower values mean more orange light – a 1,000K light source might be a candle flame, for instance – and higher values mean more blue light – 10,000K could denote a heavily overcast sky. Strongly white light exists somewhere in the middle – a value of 5,000K could apply to a camera flash, or sunlight in the middle of the day.
Setting a camera's white balance is all about getting the camera sensor to a level where under the available light, a white object appears white. Hold a candle flame close to a white sheet (well, not too close) and it'll look orange; lay out a white sheet under a very overcast day, and it'll look a little blue. A camera can compensate forthis by adding blue under very orange light or vice versa, creating a natural-looking scene in all lgihting conditions.
A camera's white balance can be fully automated, or you can control it yourself (assuming your camera offers the option). Cameras typically offer a number of white balance presets for common lighting situations. These will generally include: daylight, cloudy, shade, incandescent (domestic light bulbs) and flourescent (specifically for flourescent lamps). Some will also offer a K mode, letting you input a Kelvin value manually.
A wide-angle lens is generally defined as a lens with a short enough focal length that it displays a field of view wider than that of human vision. A wide-angle lens allows you to fit a lot into a frame – much more than the human eye would see – and is generally defined as any lens with a focal length or zoom range of less than 35mm.
A zoom lens is a lens with a focal length that can be changed. You'll see this expressed as a range in millimetres, like 10-18mm, 24-70mm or 70-200mm. A zoom lens can provide photographers with a great deal of versatility, the trade-off being that the overall optical quality tends to be inferior to that of a lens with a fixed focal length. See also: Prime lens.