Digital ImageryNecessary Multimedia Vocabulary #2

Journalism 108

Pixels

•The squares that make up a digital image. Short for “picture element.”

Bitmapped

•An image defined by a rectangular grid of pixels. Also called “raster image.”

•The computer assigns a value to each pixel.

Vectored Image

•An image which is defined mathematically rather than as pixels on a bitmap. An object-oriented image.

•A vectored image is one that stores the image content as a collection of objects that contain directions for drawing things on the screen.

Image Formats• .PSD – Photoshop’s native file format. Use

whenever you wish to maintain layers and editable text. Lossless.

• .TIF – Used mainly for images intended for print. Lossless.

• .GIF – Lossless compression; used on web for non-photographic illustrations.

• .JPG – Lossy compression with variable quality settings. Used on web for photographic images.

• .PNG – Lossless compression for photographic images on web.

Scanning

•The process of converting an analog image (negative, print, or transparency) into a digital file.

Image Resolution• Image File Resolution - W x H

The quantity of pixel information contained in the image, e.g. 1200 x 800.

• Scanner Resolution - DPIDetermines digital image file resolution

• Image Printing Resolution - PPIWhen printed, the number of pixels to be contained in each inch of the printout.

• Printer Resolution - DPIThe number of dots contained in each inch of the printed image.

Color (bit) Depth•one-bit (black and white)

each pixel either black or white

•eight-bit (256 colors on screen)

•grayscale or limited color

•sixteen-bit (65,536 colors)

•24-bit color (16.8 million colors)Full photographic color.

•32-bit color (includes 8 bits for transparency)

Examples: Bit Depth

24-bit grayscale one-bit

Grayscale

•The digital equivalent of a conventional black and white photograph.

•Contains 256 different levels of gray, from black to white.

RGB

•The “Red-Green-Blue” color mode.

•Most often used with the “color space” of monitors and images for the Internet.

CYMK•The “Cyan- Magenta-Yellow-Black”

color mode.

•Most often used for color separations.

CCD

•Charge-Coupled Device

•The light-sensitive array used to capture the image of a digital camera or a scanner.

ISO

•A measure of how sensitive your camera sensor or CCD it is to light.

• “Normal” ISO, for taking shots outdoors on bright sunny days is 100. If you’re shooting indoors, or you’re shooting, say, sports and you want to use a high shutter speed, you may need to use a higher ISO (400 is common for sports photography). ISO goes in a doubling scale too: 50, 100, 200, 400, 800, 1600, 3200.

Shutter Speed

• In photography, shutter speed is a common term used to discuss exposure time, the effective length of time a camera's shutter is open.

Aperture

• The hole through which the light passes through to reach the sensor.