Photography Jargon Buster
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This is a simple guide to understanding some of the jargon that you'll find used in the marketing spiel, or photographers using. For the purposes of this guide, it is assumed you have a digital SLR (or dSLR for the acronym lovers), which is a 35mm format camera.
Plasticbastard 20:41, 19 Feb 2006 (EST) *Copyright notice* - This article/guide is entirely copyleft. You can use it for your own purposes. Just make sure you reference the original site, and creator (plasticbastard).
In Depth Glossary Pages
Aberration: A distortion in an image caused by the lens - spherical aberration results in a loss of sharpness in the image, and chromatic aberration results in the slight separation of the incoming light's constituent colours, most often in areas of high contrast.
Aperture: An iris like gate which controls the amount of light that reaches the sensor. A smaller aperture will let less light in, while a larger aperture will let more light in. See 'f-stop' for more detail.
ASA: American Standards Association. The ASA (now ANSI) formerly held the standard used to identify the light sensitivity of film. It is now maintained by the International Standards Organisation in standard ISO 5800. The terms ASA and ISO are generally used in photography when referring to the film sensitivities to which the standards refer.
Barrel distortion: A distortion often found in zoom type lenses (at their widest focal length) which causes straight edges to curve outwards. It is most visible towards the edges of photographs.
Bayer Filter: The most common form of Colour Filter Array, the Bayer filter is arranged in a two-by-two pixel square grid, with two pixels having green filters and the other two each having a red and a blue filter. The full colour information is then interpolated after the image is taken to give the final image.
Bayonet mount: A widely used mounting type used by most 35mm SLR cameras. The lens connects/disconnects to the camera body by twisting in either a clockwise/anti-clockwise direction. Bayonet mounting styles differ from each manufacturer, however the basic connection method is the same.
Body: The camera without a lens attached.
Bokeh: This is a Japanese word that is used by photographers to describe how the out of focus sections of an image look - ie, a nice smoothe non distracting blur, or a rough, disjointed blur. While bokeh changes from lens to lens, it is also a matter of personal opinion - what may look like bad bokeh to someone in a photo, may look pleasant to another person.
Bracketing: When three or more photos are taken with different settings, it is called bracketing. Using Adobe(C) Photoshop(C) and the HDR tool, you can combine a bracketed shot with different aperture settings to produce an image with correct exposure across shadows, midtones, and highlights.
Buffer: A small (or large) amount of memory that is inbuilt into the camera to store the image while it is being processed. Once the image has been processed, it is sent from the buffer to the storage device. When a storage device (such as a compact flash card, or SD card) is in the camera, it is processed from the buffer directly to the storage device. When using 'burst mode' on a camera with this feature, and the buffer is filled, the camera may slow down the speed of which it takes photos, until the buffer is sufficiently empty to increase the frame rate.
Bulb mode: Most SLR cameras allow the shutter to be held open for a number of seconds. This setting however, allows the shutter to be held open until the shutter release is de-pressed.
Burst mode: A mode in which the camera takes a number of shots in rapid succession. As an example, the Canon EOS 20D has a burst mode of 5 frames per second for up to 23 seconds (Large JPG, Fine).
Cable release: A device used to remotely trigger the shutter release. Often used when trying to minimise the vibration caused by pressing the shutter release on the camera - particularly when working with a tripod. Some cable release devices have additional features not found on the camera itself, such as the ability to take a photo at a certain time interval, for a given length of time (ie, 5 photos every minute for 30min).
CCD: Charge coupled device. Instead of film, a camera uses a sensor to capture the image. A CCD camera is only one of many type of sensors in use in todays cameras.
Chromatic aberration: When the lens is unable to focus colours correctly on the sensor - this is more visible towards the edges of a photo, and most obvious in areas of high contrast. A lens with special glass elements to correct this issue is called an achromatic or apochromatic lens.
CMOS: Complementary Metal-Oxide Semiconductor - another type of sensor used in modern cameras to capture the image. CMOS sensors (particularly Canon made) often produce less noise than other types.
CMYK: Cyan, Magenta, Yellow, Black. These are the four colours used in various combinations to achieve the desired colour, mostly in the printing industry, and in most computer printers.
Colour Filter Array: Three CFAs are most commonly employed on digital imaging sensors. The most popular design is the Bayer filter, with the only two other noteworthy designs being the SuperCCD array used by Fujifilm, and the Foveon sensor used by Sigma.
Crash zooming: Zooming in or out while depressing the shutter.
Crop factor: This is used in reference to cameras that are not full frame, and indicates the size of the sensor relative to 35mm film. The diagonal dimension of a sensor is equivalent to the diagonal dimension of 35mm film divided by the crop factor. Typically crop factors are either 1.5 or 1.6, however they will and do vary from manufacturer to manufacturer. The Canon EOS 20D has a 'crop factor' of 1.6.
Crop factor is sometimes also referred to as the "focal length multiplier," even though the focal length of the lens hasn't actually changed, and it is more correctly termed a 'field of view crop' - an example of this is the aforementioned 1.6x crop camera, in which the use of a 50mm lens results in photos that appear the same as those taken with an 80mm lens on a 35mm film camera.
Crop factors of common digital SLRs as compared to 35mm film:
- Canon EOS 1Ds, 5D - 1.0
- Kodak DCS 14n, DCS SLR - 1.0
- Nikon D3 - 1.0
- Canon EOS 1D - 1.3
- Leica Digital Modul R - 1.4
- All Fujifilm dSLRs
- All Konica-Minolta dSLRs - 1.5
- All other Nikon dSLRs - 1.5
- All Pentax dSLRs - 1.5
- All other Canon dSLRs - 1.6
- All Sigma dSLRs - 1.7
- All Olympus dSLRs - 2.0
Depth of Field: Depth of Field (or DoF) describes the area that is either in focus, or out of focus, within an image. DoF affects all objects/subjects that are in front and behind the item being photographed. Depth of Field can be controlled by adjusting the aperture. For instance, a smaller aperture results in a larger DoF - inversely, a larger aperture results in a shallower DoF.
Diffraction: In regards to 35mm format photography, diffraction (the way light bends as it passes through, or around objects in its path) primarily becomes an issue at f-stops ranging between f10 and f32 - primarily, the sharpness of the resulting photo can decrease as the f-stop is increased (i.e. a photo taken at f8.0 is sharper than the same photo taken at f22). Most lenses have a sweet spot in their aperture range, which is usually f8-f12 (depending on the lens, and it's construction type). It is (usually) within this range that the best results for a sharp photo can be found.
Digic: Digital Image Core. A proprietry computer chip that process the image within the camera. The current version is the Digic II. Digic processors (particularly the current Digic II) are well known for their extremely fast and accurate processing capabilities - for instance, the Canon EOS 20D has a burst rate capability of 5fps up to 22 frames (in Large JPG Fine mode), or 5fps up to 6 frames in RAW+Large JPG Fine mode. The speed of the processor is due to the processing being done by hardware, instead of software.
DPI: Dots per inch. The number of dots printed in an inch of an image. Dot size at 72dpi is larger than the dot size of 300dpi - thus the higher the DPI, the more detail an image will have. DPI properly relates to print resolutions and not screen resolutions, the latter uses PPI (Pixels per Inch)
EF: Electro-Focus. The current lens mount used by Canon cameras. It is a bayonet type mount with an exclusively electrical interface to the camera body.
EF-S: A new lens type made by Canon which has been designed to fit the newer dSLR's that don't use a full frame sensor. The rear element of the lens is closer to the camera mirror. A new mounting orientation makes it physically impossible to use on a EF based camera. Camera bodies made by Canon that are able to use this type of mount are the 1.6x field of view crop cameras, such as the EOS 20D, EOS 30D, EOS 40D, EOS 350D, EOS 400D, and the EOS 450D.
EOS: Electro Optical System. A 35mm film and digital camera product range made by Canon.
EXIF: Exchangeable Image File. A recording of data attributes to an image which describes the settings used by the camera to record the photo. EXIF data can include the length of exposure, focal length, shutter speed, ISO rating, and various other useful datasets. This DATA is typically stored with the file itself (either JPG, or RAW, or other format which supports this data).
Exposure: A term used to identify the action or result of taking a photo, or relating to the settings used for taking a photo.
F-stop: A measurement of the hole created by the aperture blades. This is often indicated by fx - where x is a numerical value.
f-stops are the number of times the aperture hole will divide into the focal length. For instance, an f4 is an aperture size of 25mm in a 100mm focal length lens. To determine the f-stop, divide the focal length by the aperture size (both measurements are in millimetres). To get the hole size of the aperture, divide the focal length by the f-stop.
The f-stop scale typically ranges from f/1.4 through to f/22, though some lenses can go to f/1.0 or f/32. In this instance, the bigger the f-stop, the smaller the aperture hole, and the smaller the number, the bigger the aperture hole.
Low to mid entry zoom lenses may have an f-stop which changes at points in the zoom range. For instance, the 17-85mm lens sold by Canon has an f-stop of 4-5.6. This means that at 17mm, the f-stop can be set to a maximum of 4. At 85mm, the f-stop can be set to a maximum of 5.6.
Field of view: Used to describe how much of an image can be seen on the horizontal and vertical planes - a diagonal field of view is also quoted when dealing with rectangular images. The field of view is not fixed by the lens, nor the sensor, instead it is determined by the two combined. For example, a full frame sensor with a 28mm lens will have a different field of view than a smaller sensor with the same 28mm lens.
Filter: A piece of glass which is attached to the front of the lens to change the way light enters the lens. There are many different types of filters:
- UV or Skylight filter: Filters UV frequencies from the incoming light. This was useful for film photography, where photographic film is sensitive to UV. Digital sensors aren't as sensitive to UV so these filters are most commonly used to protect the lens itself.
- Polarising filter: Polarises the incoming light, which can be useful for the removal or exaggeration of reflections from surfaces such as water, and darkening the sky.
- Neutral Density (ND) or Grey filter: A filter that attenuates all light wavelengths equally, resulting in a darker image. They are useful for reducing shutter speeds if needed.
- Graduated filter: A type of filter that has a gradient between a colour and clear. Graduated ND filters for instance can be useful for darkening skies if they are too bright to better match the exposure to the actualy object of the scene, rather than the sky.
- Colour filter: Various types of filters exist with different colours, for example a warming filter which shifts the image slightly towards red, or a sepia filter.
- Star filter: A filter that introduces star like effects to point light sources in the image, often seen in movies.
Firewire: An adaptor aimed at connecting devices to computers with minimal fuss. It differs from USB in that it has various revisions that offer faster speeds. It is also a defacto standard for digital video cameras and capture from those devices.
Fish eye: A lens that purposely distorts the way an image is recorded, so that it has a larger field of view.
Fixed focal length: A lens which does not move the focal length of the lens forwards or backwards - the focal length is set at one distance. Also called prime lenses.
Flash: A powerful light that illuminates momentarily while the camera's shutter is open. This is used to enhance the lighting conditions of the subject.
Focal length: Simply put, this is the measurement of a lens' magnification capability. For the technically inclined, it is a measurement from the sensor to the optical centre of the lens. For example, with a 50mm focal length lens, the optical centre of the lens sits 50mm away from the sensor. Complex formulae are used to measure the focal length of a lens, and they are always stated in millimetres.
Traditionaly there are three terms used to describe a lens' focal length. They are normal, telephoto and wide:
- A 'normal' lens is usually the cheapest and best lens made by a lens manufacturer. On 35mm film/digital cameras these lenses have a focal length of 50mm.
- A 'telephoto' lens has a long focal length which allows you to get closer to a subject from a distance. On film cameras focal lengths longer than 60mm are considered to be telephoto.
- A 'wide' lens has a short focal length and a wide field of view - hence the name - that makes objects further away appear smaller. This effect can also be enhanced by clouds in a picture leading in towards the centre of the image at a very dramatic angle. Even though the distortion does not appear natural, when the image is viewed closely, it will appear normal. Typically on film cameras the focal lengths of wide lenses are below 40mm.
Zoom lenses which have a 'wide' focal length to a 'telephoto' cover a range of focal lengths by adjusting where the optical centre of the lens is located. A good example of this is the 17-85mm zoom lens that can be purchased for the Canon EOS 20D. At its widest focal length, it is 17mm - at its furthest it is 85mm; it also covers all distances in between.
On most zoom lenses, the common focal lengths are marked on the outside barrel. To set to that focal length, a rotating barrel is typically turned in either a clockwise/anti-clockwise direction.
To add confusion, there is a common misconception that digital SLRs with "cropped" sensors multiply the focal length of the lens. It should be noted that the focal length is a physical property of the lens, and not subject to the outside influence of the camera's sensor. This arises from the fact that an 18mm lens on a camera with a 1.5x crop factor will deliver a photo that looks the same as one taken with a 27mm lens on a film camera. The DSLR's image appears to have had its focal length multiplied by 1.5x, when the effect is simply the result of the field of view being reduced by the sensor. The same effect could be achieved by taking a negative produced by the film camera with the 18mm lens and cutting the edges off to give a negative the same size as the DSLR's sensor.
Some people also use field of view to describe what category a lens will fall into, however for the most part, lenses are defined by their focal length. It's important to note that different formats (such as medium and large format film types) have different classifications for their lens focal lengths. For instance, when using the 5"x4" format, a 90mm lens is considered a wide angle lens, while on a 35mm format camera, a 90mm lens is considered telephoto.
Foveon Sensor: The Foveon X3 sensor is used in Sigma digital SLRs. It differs from the Bayer sensor in that each pixel records full colour information, rather than a single colour. As a result it delivers a lot more detail than a Bayer sensor for the same image size. The 3.4 megapixel sensors in the Sigma DSLRs are generally accepted to be able to deliver detail roughly equivalent to a DSLR with a Bayer sensor between 6 and 10 megapixels, depending on the subject.
FPS: Frames per second. The number of 'exposures' a camera can take in a second. Quicker is not necessarily better, as speed may come at the sacrifice of image quality.
Frame: A single photographic exposure. Alternatively, frame is also referred to as the composition of the photo.
Full Frame: A term frequently used to refer to digital SLR cameras that have sensors the same size as a 35mm film frame, and thus having no crop factor.
Frame rate: The rate at which a frame is taken - typically expressed as frames per second (fps). A Canon EOS 20D is capable of taking up to 5fps for up to twenty-three seconds whilst in burst mode (Large JPG, Fine).
Gels: A filter style used in lenses. They can be used to colour correct, or apply other affects to light passing through the lens.
Grain: The film equivalent of noise.
Hood: A device connecting to the front of the lens which minimises the amount of light entering from the side of the lens. They are used to reduce lens flares. Hoods must match the focal length of the camera, or vignetting (or other unwanted distortions) can occur.
Hot Shoe: A connection jack that allows flashes, or other devices to be plugged into the camera, expanding on the camera's abilities. The camera neither has to be on or off for most accessories to be added or removed.
Image bank/tank: A device which has a laptop sized harddrive, and either a USB or Compact Flash/SD adapter in it. You are able to download your images onto this device, and if equipped with a screen, you can view or do basic edit tasks. The device is typically portable, and approximates to a small iPod size.
ISO: This is the internationaly recognized standard to measure the light sensitivity of a film. Typically, a low ISO rating denotes a 'slow' or low sensitivity to light, hence requiring either a longer exposure (ie, the shutter stays open for longer) or a wider aperture. ISO ratings work on the principle of doubling the sensitivity, doubles the rating. For instance, ISO 200 is twice as sensitive as ISO 100, thereby requiring less exposure time, or a narrower aperture.
Another way to explain this, is that for every doubling of the ISO rating, you halve the amount of light needed to take the photo; which is why a high ISO allows you to take photos in a low light environment without a flash or extra light sources.
ISO ratings also impact on grain/noise issues within photographs. For instance, taking a photo in a dimly lit environment (ie, at night) with a high ISO rated sensor/film will cause a lot of noise in the image. The reverse is also true. However, this can all be controlled via the use of a flash, or using an appropriate ISO rated film/sensor. Digital SLR's are able to adjust the ISO setting of the sensor. Unfortunately for those with digital point and shoot cameras, you are often locked in with a specific ISO rated sensor.
JPEG: Joint Photographic Experts Group. Because of it use of compression, it is able to make the file size smaller or larger, at the sacrifice of image quality. It is considered a defacto standard for storing photos.
K mount: The bayonet style mount used by Pentax.
Kit lens: The lens supplied by the manufacturer with a camera body. It is often an entry level lens which suits most users needs. Professional photographers tend to either not use the kit lens, or purchase the camera body seperately.
L series: Often used in reference to Canon lenses. The 'L' series lens made to a higher quality standard than the average lens. The lens barrel is typically completely weatherproof, and the glass elements are made from a higher quality glass, resulting in crisp, clean, and well focussed shots.
Lens hood: A plastic (or other material) 'cup' attached to the lens to minimise flaring from stray light, and to reduce stray light entering the lens. Some lenses have inbuilt hoods, others are attached via thread mount, or someother form of mount. Lens hoods are not always included with lenses, however some lenses come with these.
Lens speed: Lens speed is directly related to the maximum f-stop a lens can go to, ie, an f2.8 lens is faster than an f4 lens.
Light meter: A device used to measure light in either a scene, or of a particular object to calculate the correct exposure settings for the photo.
Lossless: Used to describe a file format in which the file size is reduced, but image quality is not sacrificed. Typically, lossless formats don't offer control over how the image is compressed.
Lossy: Used to describe a file format in which the file size is reduced by removing certain information from the image. Typically, lossy formats offer a method to control how much image quality is kept or removed.
Macro: A form of photography specialising in extreme close-ups of objects. Generally, a prime lens is used with a focusing point extremely close to the lens - this lets the camera get a lot closer to the object than what non-macro lenses would be able to achieve (note that macro lenses can be used like any other lens, they can just focus closer to the lens).
Macro photos are also spoken of in terms of life size or non life-size. A life-size macro image is considered 1:1, while double life-size is 2:1 - inversely, 1:2 is half life-size. This ratio indicates how large the projected image of the object is on the camera's imaging plane.
Megapixel (or Mp): This is the measurement of pixels in an image. The pixel counts are usually taken from the entire sensor, while the imaging area of the sensor is slightly smaller. As a result the number of pixels in the final image is usually slightly less than what is quoted, but the difference is usually no more than 1%.
The more pixels per image, the bigger the image is. For instance a 4.1Mp camera takes a picture that has half that of an 8.2Mp camera. Since this is a two dimensional measurement, the 8.2MP image isn't twice as wide or high as the 4.1MP image, though it does have twice the area. Most cameras have a number of image sizes that can be selected before the photo is taken.
There is some argument amongst many photographers that small jumps in the amount of pixels in a sensor is not worth the increase in cost - ie, the jump from 8.2 to 10.2 is not as big as the jump from 4.1 to 8.2.
Increasing the number of pixels in a sensor without also increasing its physical size also reduces its sensitivity - all other things being equal - as less photons are collected by each pixel. As a result the low light performance of fixed lens cameras - which traditionally have small sensors - has been steadily decreasing as their pixel counts increase.
Microdrive: Originally made by IBM, this was a complete and working harddrive in a Compact Flash format. These drives are now made by Hitachi.
Mirror lock-up: A feature on most SLR cameras that uses the inbuilt timer feature to lock the mirror into the up position, before the shutter is opened. This reduces camera vibration, and thus minimises the chance of an out of focus, or blurred image for shutter speeds around about 1/30s.
Monopod: A monopod is essentially a stick with a tripod mount at the top (usually just a threaded bolt stem) that allows a photographer to stabilise the camera without having to carry a tripod everywhere. Monopods range from a simple wooden stick to telescoping carbon fibre poles with a pop out tripod legs at the bottom.
Often used at sporting events to carry the weight of large telephoto/zoom lenses.
Negative: The film equivalent of a sensor. The negative captures light, and through a chemical reaction, the grain on the film is exposed to the correct colour.
A negative is always the reverse colour of the photo taken. Exposing the negative onto photographic paper exposes the colour correctly. Thus a photo is born.
Nodal point: The point at which light entering the camera/lens is focused. This term is often used in panoramic photography, as it is the point at which all parralax errors are corrected.
Noise: This is the digital equivalent of graininess in film. Essentially, as the ISO sensitivity of the sensor increases, the amount of noise (or pixels that haven't exposed correctly) increases. This results in an image that has a lot of incorrectly exposed pixels. To minimise noise, the ISO sensitivity is either lowered, or a noise removal filter in a graphic editing program (or a standalone tool) can be used.
Open flash: Multiple flash firings used during a long (usually 'bulb') exposure to increase the amount of light in the image. Only used when lighting levels are practically non existant, however, artistic affect can be created by doing this on purpose.
Over exposed: To much light has been captured in the image, and parts of the image will look washed out as a result - specifically the highlights.
Pano rail: Also known as a pano head. This is a mounting bracket that allows the camera to be positioned as such that the lens is rotating on its nodal point. This type of mount is usefull for creating panoramic images, as it reduces parralax errors - virtually creating a seamless panoramic photo without having to use software to fix perspective/parralax errors.
Photochop / Photoshopped / Photochopped: Editing a photograph in either Adobe(C) Photoshop(C), or other such program.
Pincushon affect: A distortion in an image where straight lines are curved inwards. This is caused by the lens.
PPI: Pixels per inch. The number of pixels displayed per inch in an image viewed on a computer. This term is interchangeable with DPI, however, DPI is usually used in reference to a printed image. In order to find the physical printed size of an image of a given PPI, one takes the resolution and divides each by the PPI - ie, an image 1920x1200 at 300PPI will print at 6.4inches by 4inches (1920/300 and 1200/300).
Quick release: A tripod mount that is attached to the camera to allow quick removal/installation of the camera to a tripod. Typically this is by a threaded screw attached to a mounting plate, which slips into a special bracket on the tripod.
RAW: The image taken by a camera exactly how the sensor see's it, without any post processing done by the camera's internal processor. Many manufacturers have their own proprietry format of the RAW file, however, all of these various formats accomplish the same thing - recording the image without additional processing.
Many dSLRs allow the user to choose RAW, RAW+JPG or RAW+TIFF.
Reel: A device used to hold film in older film cameras. May also be referred to as a spool. Reels are also used in developing rolls of film.
Reflector: A simple device that reflects light from a source (such as a lamp, or sunlight) onto the subject. Reflectors are typically white, however, they can be any colour, depending on the desired effect. Typically used when 'filling' light on a subject.
Resolution: The width X height of an image displayed on a monitor, or the dimensions of a photograph. Typically indicated as a measurement of pixels - ie, 1920x1200 is the native resolution of the Dell 2405 24" TFT screen.
Sheet film: Film cut into sheets, typically used in larger format photography, specifically where film with a footprint larger than 4x5 inches.
Shutter: The shutter is the part of the camera that opens and closes like a curtain to allow light from the lens to pass through to the sensor.
- Shutter lag: The time it takes from when the shutter release button is pressed, to when the shutter opens. Older point and shoot cameras, and some SLR's often had lag up to one or two seconds before the shutter was opened.
- Shutter speed: The amount of time it takes for the shutter to open and close. On most SLRs the shutter speed can be manually controlled. The Canon EOS 20D has a shutter which can open and close in 1/8000th of a second, or be set to stay open for as long as the shutter release button is held down.
Silhouette: An image in which the foreground is completely black, and the background is well lit. No foreground detail can usually be seen.
Spool: A cylindrical device used to hold film for use in an older film camera. Typically in 35mm format film, a spool will sit inside a canister designed to make loading and unloading of film as easy as possible. In medium format cameras, two spools are used, one holding the film prior to taking photos, and the other which the film is advanced/taken up on by the movement of the motor mechanism or manual wind mechanism.
The difference between the two formats is that with 35mm format film, the film is loaded onto a sprocket mechanism which advances the film (either motor or manual advance), and when the roll is finished, a motor rewinds the film back into the canister. With the medium format system, two spools are used, with film advancing to the other spool as photos are taken. The medium format system requires the use of an empty spool at all times.
SuperCCD: The Colour Filter Array employed by Fujifilm in some of its camera designs. It differs from the Bayer filter in that its grid of pixels is rotated by 45°, and the pixels themselves are octagonal, resulting in a honeycomb pattern. The small spaces between each cluster of four pixels contain a smaller photosite that measures the luminance or brightness at that point, rather than colour. The result is that once the image is interpolated, it contains more dynamic range and more detail than an image of the same size from a Bayer sensor of the same physical size.
TIFF: Tagged Image File Format. A lossless compression format used in photography/graphical editing. It is considered superior compared to JPEG because it doesn't compress the image.
Tranny: Slang for transparency film of any format.
Tripod: A three legged device with a special mounting device that allows the user to steady a camera. Often used for macro, or landscape photography, where camera stability and minimal vibration is crucial.
TTL: Through the lens - a metering method that allows the camera to gather the information about the light in a particular scene. The camera has an inbuilt computer and sensor to correctly determine the best settings for taking the picture. It is also a quick and dirty way to evaluate the light in a particular scene without resorting to an external light meter.
Under exposed: Not enough light was captured in the image, and shadows/midtones are too dark.
USB: Universal Serial Bus. An adaptor which aims to make connecting devices to computers easier. Currently in its second revision.
Viewfinder: The part of the camera in which you can see the image before you take a photo.
Vignetting: When the corners of the photo are darker than the rest of the image. Usually caused by abnormalaties with the lens, however, an incorrectly matched hood, or too many filters can also cause this distortion.
White balance: The way white looks in a particular photo under certain lighting conditions. Most modern SLR camera's often allow you to specify a custom white balance to correct for different lighting conditions.
Zoom: A lens which is able to move from a smaller focal length, to a longer focal length. For SLR cameras, it is represented in millimetres, while most point and shoot cameras represent them as 'times' (ie, 5x zoom). Zoom lenses are useful when you want to choose between a wide focal length, or a long focal length, without having to swap lenses, or carry multiple bodies with different lenses attached. Most camera kits include a basic zoom lens.
plasticbastard - 2006 | References to Canon in this wikipage are because it is the only dSLR I have at my disposal. I am not affiliated with Canon in any way, other than the fact I own one.