Class+Vocabulary

Parts of this sheet were copied from the Kodak INTERNET Site Lossy Compression - To save space lossy compression throws away parts of an image. Obviously you can't just go around discarding any old piece of information so what the JPEG algorithm does is first divide the image into squares (you can see these squares on badly-compressed JPEGs). Then it uses a piece of mathematics called Discrete Cosine Transformation to turn the square of data into a set of curves, some small, some big, that go together to make up the image. This is where the lossy bit comes in: depending on how much you want to compress the image the algorithm throws away the less significant part of the data (the smaller curves) which adds less to the overall "shape" of the image. However the lossy compression method can generate **artifacts** - unwanted effects such as false color and blockiness - if not used carefully. Memory card —A storage device used to store data, such as picture and movie files. Available in a range of sizes, such as 8 MB, 32 MB, and 256 MB.
 * Pixel **—(PICture ELement) The smallest element of a digitized image. One small dot of light among the many dots that make up an image on a computer screen.
 * Megapixel **—A unit equal to one million pixels. The higher the resolution, the more pixels in an image and therefore the greater the image quality. An image file that is 1 megapixel (MP) can make a photo realistic print of 5 x 7 inches; a 2 MP file can make an 8 x 10-inch print; a 3 MP file can make an 11 x 14-inch print.
 * Resolution **—The number of pixels in an image. A higher number correlates to a higher quality image.
 * DPI **—Dots Per Inch. Number of dots a printer or device (like a monitor) can display per linear inch. For example, most laser printers have a resolution of 300 dpi, most monitors 72 dpi, most PostScript image setters 1200 to 2450 dpi. Photo quality inkjet printers now range from 1200 to 2400 dpi.
 * PPI **—Pixels Per Inch. The number of pixels per linear inch is used to describe image resolution. A higher ppi means more image detail and correlates to higher image quality. Monitors display images at 72 ppi, inkjet printers require at least 150 ppi to produce photo realistic prints.
 * Megabyte **—An amount of computer memory consisting of about one million bytes. The actual value is 1,048,576 bytes.
 * Kilobyte **—An amount of computer memory, disk space, or document size consisting of approximately one thousand bytes. Actual value is 1,024 bytes.
 * JPEG **—A standardized format used by many digital cameras for storing images. This format is also commonly used for images on the web and images attached to e-mail messages. JPEG, which stands for Joint Photographic Experts Group, the group that established this file standard, is one of the most widely, used formats today. JPEG is a standardized image compression mechanism designed for compressing full-color or gray scale images of natural, real-world scenes. JPEG uses lossy compression, which can damage image quality. Every time you save an image in JPEG format you degrade the image further. Images should always be saved as PSD to protect quality
 * LCD **—Liquid Crystal Display. A full-color display screen on cameras used to preview and review pictures and view information, such as menu options and camera settings.
 * Digitize **—To convert analog information into digital format for use by a computer.
 * Photo kiosk **—A stand-alone computer-run system that allows users to edit and print pictures from negatives, prints, or digital files on a picture card, CD, or disk. The kiosks are usually located in retail store.
 * PSD** A standardized format used in Photoshop images it stands for Photoshop Document. While this is the best way to preserve image quality it is is not viewable by computers that do not have Photoshop.
 * Online photo service **—An online photofinishing service that lets digital and, at some sites, film camera users share and store their photos in online photo albums and order high quality prints from digital images. The sites lets users enhance pictures with editing tools, order prints online and order other photo products, like calendars and cards. Some samples are [|photobucket] and [|Flickr]