Digital Camera Glossary
Contributed by: Niles
Additive Color
A colorspace in which light is added to black to achieve a color and tone. RGB is an additive color system in which Red, Green, and Blue light are combined to make white.
Alpha Channel
is a mask channel in addition to the three Red, Green, & Blue image channels that can be used to isolate a particular area of an image in order for the computer to perform operations on that particular area. Alpha channels are used to describe silhouettes that have soft edges.
Array Camera
a digital camera that uses a large CCD chip (an array of rows and columns of light sensitive pixels) to sense the entire image at one time as opposed to scanning the image one row of pixels at a time.
Artifact
any artificial glitch or blemish inadvertently created in or by the digital process.
Bandwidth
refers to the amount of data that can be transferred over the Internet in a given amount of time. A 14.4 kbps modem has a very narrow bandwidth and is very slow. A T-100 ISDN link has a broad bandwidth and is very fast.
Bit Depth
The number of binary data bits used to record the brightness of each pixel per color channel. To achieve the illusion of ``continuous tone" requires 256 levels of brightness from black (0) to white (255). This requires 8 bits binary. Since it takes three channels (Red, Green, & Blue) to represent color, we need 24 bit (3x8) color to achieve ``full color" RGB output and 32 bit color for CMYK. A bit depth of 48 (16 bits per channel RGB) records 65,536 levels of gray per channel. If the number given for bit depth is greater than 16 and is not divisible by 3 then it is probably referring to 4 channel CMYK.
Bit-Mapped
images represent the artwork as a grid of colored dots called Pixels. Paint and image-editing programs such as Painter and Photoshop are bit-mapped images.
Brightness
The apparent level of light emitted by or reflected from an object. The Brightness Range of an image is measured from the darkest black to the brightest white.
CCD
a Charged Coupled Device is a type of electronic solid-state semiconductor device that is extremely sensitive to light. These devices are assembled on integrated circuit chips into either long rows for scanning devices or into arrays of rows and columns for digital and video cameras.
Calibration
the process of adjusting a monitor or scanner to a repeatable standard. A monitor is adjusted to a specific contrast (Gamma), brightness, and whitepoint color balance.
Capture
a digital camera is said to Capture an image rather than Take a picture.
Characterization
the process of building a Look-Up-Table (LUT) for a calibrated monitor. By profiling the output of numerous key colors from a monitor a LUT can be created that allows the computer to substitute corrected (Characterized) colors to achieve consistent and accurate output.
Colorspace
There are numerous methods of creating or describing a specific color and tone. These different models are called Colorspaces. examples are RGB, CMYK, LAB, YCC.
Depth Of Field
A photograph that shows the area close to the camera and things far away all in good focus is said to have a large depth of field. A narrow depth of field is when only a thin section of the scene, say from ten to twelve feet away from the lens, is in focus.
Digital Zoom
In some digital cameras the manufacturer makes the choice to not include an optical zoom lens. This makes the camera quite a bit smaller as can be seen with some of the pocket-sized digitals on the market. Some of those pocket cameras offer digital zoom. The camera takes a portion of the image and magnifies it digitally. Unfortunately, these images get fuzzy in a hurry because a smaller amount of information is being used to create a larger image because the camera has to create the missing information.
Memory Cards
These are small memory modules that can be inserted into the camera to hold images. When the card is full it can be removed and another card inserted. The memory on these cards is non-volatile-m that is, they don't lose their images when they are removed form the camera. The images can be later downloaded from the card, and when the images are erased from the card it is ready to be reused.
Multi Capture
Allows a number of pictures to be captured in fast succession. It is the electronic counterpart to motor drives and power winders in film cameras. It allows the camera to take a series of pictures, one right after another, by holding down the shutter release. It can take pictures as fast as from two to four frames per second. As many as from eight to twenty pictures can be captured at one time. The speed and number of frames varies depending on the specific brand and model of camera. This is almost always accomplished in lower resolution modes with the flash off to limit the amount of memory needed and increase the speed of the capture.
Self-Timer
The self timer allows the camera to take a picture unattended. With it you can take a picture of yourself. Once the timer is set, you usually have about ten seconds to get into the picture. A flashing light or a tone signals when the picture is about to be taken.
Under-Exposed
An under exposed picture means that too little light was allowed to strike the film (or the proper amount of light was allowed to strike the film for too short a period of time). That means that the aperture was too small for the exposure time, or the exposure time was too short for the aperture opening. This will give an image that is too dark.
White Balanced
This is the ability of the camera to adjust the color balance of a picture to compensate for the ambient lighting. It is easy to see that fluorescent lights have a different color from incandescent lights. These are both different from the light that a photo flash gives off, and they are all different from the color of the light from the sun. This is often adjusted automatically in digital cameras, and it makes picture taking easy. If a camera possesses this function it is said to have "auto white balance."
Zoom Lens
Some lenses have the ability to change their magnification level through a range of focal lengths (wide angle through telephoto). This is called a zoom lens as is seen on most all camcorders. With digital cameras the range varies by brand and model, but ranges in the area of 35mm to 115mm are fairly common. This range would often be referred to as "3X" (three times) zoom (3x35=105, so the telephoto setting is about 3 times the wide angle setting). The best cameras achieve this by moving various elements in the lens. This would be referred to as optical zoom. Cameras using optical zoom are generally larger than those without because of the more complicated and thus larger lens elements.
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