Year 10 Digital Photography
A Glossary of Terms for Compact Digital Cameras
APERTURE
Definition: The aperture is the size of the adjustable opening inside the lens, which determines how much light passes through the lens to strike the image sensor. A digital camera's aperture is measured in f-stops, and higher f-stops signify a smaller amount of light. The aperture changes, depending on the camera's settings for a particular shot.
Beginner-level digital cameras usually control aperture automatically. With more advanced digital cameras, a photographer might be able to control the aperture setting manually or allow the camera to set it automatically.
AUTOFOCUS
Definition: Autofocus is a capability of a digital camera to automatically bring the subject of a photograph into sharp focus before capturing the digital image. Most beginner-level digital cameras only allow autofocus. Manual focus usually is limited to advanced digital cameras.
AUTOMATIC EXPOSURE
Definition: Automatic exposure (AE) is an automated digital camera system that sets the aperture and/or shutter speed, based on the external lighting conditions for the photo. With beginner-level digital cameras, photographers usually can select one of three different AE modes.
* Aperture priority allows the photographer to set the aperture value, and the digital camera then determines the shutter speed. This is called a semi-automatic exposure.
* Shutter priority allows the photographer to set the shutter speed, and the digital camera then determines the aperture setting. This also is called a semi-automatic exposure.
- Program mode is a fully automatic mode, where the camera sets shutter speed and aperture. This mode sometimes is called Program AE.
AUTOMATIC MODE
Definition: Automatic mode is a mode in a digital camera where the camera's software fully controls all aspects of the photograph, from the shutter speed to the aperture setting to the focus. The photographer has no specific control over the settings for a particular photograph.
Contrast this with manual controls, where the photographer can set any aspect of the camera's settings manually. Most digital cameras have a fully automatic mode. Advanced cameras often have both manual and automatic modes, while point and shoot cameras have only fully automatic modes.
BATTERY
Definition: The battery is the portable electric power source used to operate a digital camera.
Two types of digital camera batteries are used. A proprietary battery is a unit that only fits one or a few digital camera models. Such batteries usually are square or rectangular in shape, and they're rechargeable.
An alkaline battery is a mass-produced type of battery that you usually throw away after use, such as a cylindrical AA or AAA battery. Such batteries have many different uses for consumer electronics devices.
Digital cameras typically can only use one type of battery.
CCD
Definition: A CCD, short for charge coupled device, is the silicon chip inside the digital camera that records the image.
The CCD contains millions of capacitors. As light enters the camera through the lens, it strikes the CCD's photoactive layer, which causes each capacitor to accumulate an electric charge based on the amount of light that strikes it. The digital camera then converts the charge to pixels that make up the photo.
A CCD uses a slightly different technology from CMOS, another type of image sensor found in digital cameras. CMOS is the more popular technology.
CMOS SENSOR
Definition: A CMOS sensor is a type of image sensor inside a digital camera consisting of an integrated circuit that records an image.
The complementary metal-oxide semiconductor (CMOS) sensor consists of millions of pixel sensors, each of which includes a photodetector. As light enters the camera through the lens, it strikes the CMOS sensor, which causes each photodetector to accumulate an electric charge based on the amount of light that strikes it. The digital camera then converts the charge to pixels that make up the photo.
CMOS uses a slightly different technology from CCD, another type of image sensor found in digital cameras. CMOS is becoming the more popular type of technology because of its low power consumption and speed.
Also Known As: complementary metal-oxide semiconductor sensor
COMPACT FLASH
Definition: CompactFlash (CF) is a type of flash memory card used in digital cameras to store data about images. CF cards are available in two configurations: Type I and Type II. Type I cards are slightly thinner than Type II cards. If a digital camera has a CF Type I slot, it cannot use Type II memory cards. However, digital cameras with CF Type II slots can read both types of CF cards.
CF cards larger than 2GB (gigabytes) in capacity use a slightly different storage technology than CF cards at 2GB and smaller capacities. Some digital cameras that use CF cards cannot read CF cards with more than 2GB of storage capacity because of the change in storage technology.
SanDisk developed the first CF cards in 1994. CF cards are some of the largest memory cards, and they're almost square in shape. CF cards measure 43 mm by 36 mm (1.69 x 1.42 inches). Type I cards measure 3.3 mm in thickness (0.13 inches), while Type II cards measure 5 mm in thickness (0.20 inches).
DIGITAL IS (Image Stabilisation)
Definition: Digital IS (image stabilization) is a digital camera technology that works to reduce blurry photos by using software corrections inside the digital camera to compensate for camera shake. Digital IS might cause the digital camera to increase shutter speed or increase the camera's sensitivity to light (ISO sensitivity). However, by boosting these settings beyond what the camera's automatic settings should be, digital IS sometimes causes photo quality to degrade.
Contrast digital IS with optical IS, which makes use of hardware corrections inside the digital camera to compensate for camera shake as the photograph is snapped. Digital IS is not as effective as optical IS in creating high-quality photos while compensating for camera shake.
DEPTH OF FIELD
Definition: Depth of field is the section of the digital photograph in front of and behind the subject that will be in focus, too. Any objects outside of the scene's depth of field (DOF) will appear out of focus, or fuzzy. The distance to the subject, the aperture, and the focal length all affect depth of field in a photograph.
With a shallow, or narrow, depth of field, the subject will be in focus, along with anything a few feet in front of and behind the subject.
With a great, or wide, depth of field, the subject will be in focus, along with anything several to dozens of feet in front of and behind the subject.
DIGITAL ZOOM
Definition: Digital zoom is the magnification of a digital image using software inside the digital camera, rather than changing the focal length of the zoom lens to magnify the image.
Digital zoom simply increases the size of the pixels that make up the digital image, which can harm photo sharpness. Digital photographers prefer optical zoom.
ELECTRONIC VIEWFINDER
Definition: An electronic viewfinder, or EVF, is a tiny LCD at the top and back of the camera that displays the image that will be taken and that the photographer uses to frame the photo. The LCD is inside a small window. EVFs can display information about the camera's settings, but they can be tough to see in low light.
Also Known As: EVF, viewfinder
FILE FORMATS
Definition: File formats in a digital camera are the types of formatting used to store digital image files. Each of the three primary types of formatting offers a few different benefits and drawbacks.
* JPEG, short for Joint Photographic Expert Group, is the most commonly used format for digital images, especially for beginner photographers. JPEG, pronounced jay-peg, is a form of compression that reduces the file size significantly, allowing you to fit more photos on a memory card.
* RAW is the file format that's closest to film-quality, requiring a lot of storage space. The digital camera does not compress or process a RAW file.
* TIFF, short for Tagged Image File Format, uses a slight compression to reduce the file size.
Beginner-level digital cameras usually limit photographers to the JPEG file format. More advanced models allow you to choose between the three formats, and some shoot in more than one mode at one time, such as JPEG and RAW.
Also Known As: image formats
ISO
Definition: ISO is a number used to express the light sensitivity of the digital camera. ISO has its origins in film photography, where the ISO setting measured the sensitivity of a particular roll of film to light.
With a digital camera, you usually can shoot at a variety of ISO settings. Higher ISO settings allow you to shoot digital photos in low-light conditions, but such photos are more susceptible to noise and grainy images than photos shot at low ISO settings.
MEGAPIXEL
Definition: A megapixel (MP) is equal to 1 million pixels. A pixel is an individual element of a digital image. The number of megapixels determines the resolution of an image, and a digital image with more megapixels has more resolution.
Because digital cameras now often have the ability to create photographs containing 10 million or more pixels, megapixel is the preferred method for measuring resolution. In a list of digital camera specifications, you'll often see "MP" used as the abbreviation for megapixel.
MANUAL CONTROLS
Definition: Manual controls are the settings on a digital camera that the photographer controls manually. For example, a photographer may want to set the shutter speed and aperture manually to create a particular look in a photograph. The ability to manually control certain settings on the digital camera usually is limited to advanced models.
Contrast manual controls with fully automatic settings, where the camera sets every aspect of the photograph without input from the photographer.
MULTIMEDIA CARD
Definition: MultiMedia Card (MMC) is a type of flash memory card used in digital cameras to store data about images. MMC is a slightly older type of flash memory technology, and the more popular Secure Digital (SD) memory card technology is based on MMC. Some digital cameras can use MMC and SD cards interchangeably. MMC cards have a maximum storage capacity of 4GB (gigabytes).
MOVIE MODE
Definition: Movie mode is the capability of a still digital camera to shoot video clips. Nearly all new still digital cameras include at least basic movie modes. Improvements in video capabilities for digital still cameras continue at a rapid rate. Some digital still cameras can even shoot HD video.
NOISE
Definition: Noise is any of a series of unwanted variations that appear in a digital camera photo. Noise appears as strangely coloured or grainy pixels in a photo, especially as purple edges to objects, called purple fringing. Noise in a digital image is especially common in photos shot in low light.
Noise occurs because of electrical variations and interference in the image sensor. High ISO settings can create noise.
Although they have the same results, noise is not quite the same as artefacts, which are digital image distortions caused by JPEG compression techniques.
OPTICAL IMAGE STABILIZATION
Definition: Optical IS (image stabilization) is a digital camera technology that works to reduce blurry photos by using hardware corrections inside the digital camera to compensate for camera shake as the photograph is snapped. Optical IS the most precise type of image stabilization, as it uses a gyro-sensor to measure camera shake. The camera then shifts the image sensor to compensate.
Contrast optical IS with digital IS, which makes use of software corrections inside the digital camera to compensate for camera shake. Digital IS is not as effective as optical IS in creating high-quality photos.
OPTICAL VIEWFINDER
Definition: An optical viewfinder is a small window at the top and back of the digital camera that you use to frame your photograph and that attempts to match the path of the main lens. Some high-end digital cameras link the optical viewfinder to the lens, meaning the viewfinder looks through the lens, using a series of mirrors and prisms.
Also Known As: viewfinder
OPTICAL ZOOM
Definition: Optical zoom is the magnification of a digital image using physical changes in the focal length of the zoom lens to magnify the image.
Optical zoom is the preferred method of magnifying an image for digital photographers because it doesn't negatively affect image quality, as does digital zoom.
PICTBRIDGE
Definition: PictBridge is a direct-printing feature that allows you to print photos from a digital camera-to-printer connection. No computer connection is required. Both the digital camera and the printer must support PictBridge for the feature to work.
PIXEL
Definition: A pixel, short for picture element, is the smallest piece of information that makes up a digital image.
Individual pixels are tiny dots, squares, or rectangles. A digital photograph consists of millions of pixels, but the individual pixels are too small to see without magnification. The human eye naturally blends all of the pixels together to create what appears to be a seamless image.
Pixels also make up the LCD screen on the back of the digital camera. LCDs with more pixels create sharper images.
Also Known As: picture element
PROCESSOR
Definition: A processor in a digital camera is a chip that controls most aspects of image management and creation. A processor can improve image quality, increase the speed of the camera's auto-focus system, improve image compression results, and preserve battery life.
The camera's processor also controls the memory card, the LCD, and the analogue/digital convertor.
REDEYE
Definition: Redeye is an effect often seen in digital photographs and prints, where the subjects appear to have red-coloured pupils in the eyes when a flash is used when shooting the image. Redeye is caused by a reflection from the light from the flash against blood vessels in the retina of the eye. Beginner-level and low-priced digital cameras are more susceptible to causing redeye than advanced models, because the lens and flash units usually are close together in a low-priced digital camera.
To remove redeye, photographers can try to remove the effect using photo-editing software. Some digital cameras also offer a redeye reduction feature, where the flash changes the way it fires to force less light to reflect off the retina.
RESOLUTION
Definition: Resolution is the measurement of the total number of pixels that a digital camera's image sensor can record in one photograph. Digital camera resolution is expressed in megapixels, which are millions of pixels.
Theoretically, digital cameras with higher resolutions can create sharper and larger print photographs. However, high-resolution cameras don't automatically yield high-quality photos, because many factors contribute to photo quality, such as lens quality, shutter speed, and external lighting.
In a listing of digital camera specifications, you'll probably see two resolution measurements: Overall and effective. Effective pixels, or effective resolution, is the more useful number.
RESPONSE TIME
Definition: Response times are the collection of times, or delays, that occur as a digital camera functions, including startup time, shutter lag, and shot to shot delays.
Response times will vary among different models of digital cameras. A digital camera model with poor response times can be frustrating to use, because it can cause you to miss some spontaneous photos. Generally, low-priced, beginner-level digital cameras will have poorer response times than high-priced, advanced-level digital cameras.
SCENE MODES
Definition: Scene modes are pre-set exposure modes on beginner-level digital cameras that help inexperienced photographers achieve the proper automatic settings for a photo. By using a scene mode, the photographer is telling the digital camera to emphasize a certain aspect of the settings for a particular set of upcoming photos.
For example, the photographer might choose "Sports" as the scene mode when shooting at a baseball game. The digital camera then would emphasize the camera's automatic settings for a fast shutter speed to capture moving action. Another scene mode might be "Night," which tells the camera to emphasize allowing more light into the image sensor. Some cameras contain a dozen or more scene modes.
SECURE DIGITAL
Definition: Secure Digital (SD) is a type of flash memory card used in digital cameras to store data about images. SD is probably the most popular type of memory card. SD and MMC flash memory cards are similarly sized and use similar technology as SD's design was based on MMC's design, but not all digital cameras can use the two types of cards interchangeably. MiniSD and MicroSD cards are available, too, but they typically work with cell phones, rather than digital cameras. Adapters are available to make a MiniSD or MicroSD card work in a digital camera that uses SD memory cards.