HA1 - Technical File – Raster and Vector Images There are two kinds of computer graphics - raster (composed of pixels) and vector (composed of paths). Raster images are more commonly called bitmap images. A bitmap image uses a grid of individual pixels where each pixel can be a different colour or shade. Bitmaps are composed of pixels. Vector graphics use mathematical relationships between points and the paths connecting them to describe an image. Vector graphics are composed of paths. The image to the left below is representative of a bitmap and the image to the right is representative of a vector graphic. They are shown at four times actual size to exaggerate the fact that the edges of a bitmap become jagged as it is scaled up: Bitmap Image: Vector Graphic:
HA1 - Technical File – Antialiasing An anti-aliasing filter is a filter used before a signal sampler, to restrict the bandwidth of a signal to approximately satisfy the sampling theorem. Since the theorem states that unambiguous interpretation of the signal from its samples is possible when the power of frequencies above the Nyquist frequency is zero, a real anti-aliasing filter can generally not completely satisfy the theorem. A realizable anti-aliasing filter will typically permit some aliasing to occur; the amount of aliasing that does occur depends on how good the filter is and what the frequency content of the input signal is.
HA1 - Technical File – Resolution The amount of detail that the camera can capture is called the resolution , and it is measured in pixels. The more pixels a camera has, the more detail it can capture and the larger pictures can be without becoming blurry or "grainy." Some typical resolutions include 256x256 - Found on very cheap cameras, this resolution is so low that the picture quality is almost always unacceptable. This is 65,000 total pixels. 640x480 - This is the low end on most "real" cameras. This resolution is ideal for e-mailing pictures or posting pictures on a Web site. 1216x912 - This is a "megapixel" image size -- 1,109,000 total pixels -- good for printing pictures. 1600x1200 - With almost 2 million total pixels, this is "high resolution." You can print a 4x5 inch print taken at this resolution with the same quality that you would get from a photo lab.
HA1 - Technical File – Aspect Ratio The aspect ratio is an image projection attribute that describes the proportional relationship between the width of an image and its height. It is expressed as two numbers separated by a colon. That is, for an x : y aspect ratio, no matter how big or small the image is, if the width is divided into x units of equal length and the height is measured using this same length unit, the height will be measured to be y units. For example, consider a group of images, all with an aspect ratio of 16:9. One image is 16 inches wide and 9 inches high. Another image is 16 centimeters wide and 9 centimeters high. A third is 8 yards wide and 4.5 yards high.
HA1 - Technical File – File Formats The three most common image file formats, the most important for printing, scanning and internet use, are TIF, JPG and GIF. However, TIF cannot be used in internet browsers. All editor programs like Adobe Photoshop or Adobe Elements support these file formats, which will generally support and store images in the following colour modes: TIF RGB - 24 or 48 bits, Grayscale - 8 or 16 bits, Indexed color - 1 to 8 bits, Line Art (bilevel)- 1 bit For TIF files, most programs allow either no compression or LZW compression (lossless, but is less effective for 24 bit color images). Adobe Photoshop also provides JPG or ZIP compression too (but which greatly reduces third party compatibility of TIF files). "Document programs" allow ITCC G3 or G4 compression for 1 bit text (Fax is G3 or G4 TIF files), which is lossless and tremendously effective (small). PNG RGB - 24 or 48 bits, Grayscale - 8 or 16 bits, Indexed color - 1 to 8 bits, Line Art (bilevel) - 1 bit PNG uses ZIP compression which is lossless, and slightly more effective than LZW (slightly smaller files). PNG is a newer format, designed to be both verstile and royalty free, back when the LZW patent was disputed. JPG RGB - 24 bits, Grayscale - 8 bits JPEG always uses lossy JPG compression, but its degree is selectable, for higher quality and larger files, or lower quality and smaller files. GIF Indexed color - 1 to 8 bits GIF uses lossless LZW compression, effective on indexed color. GIF files contain no dpi information for printing purposes.
HA1 - Technical File – Colour Models The Two Most Common Color Models There are several established color models used in computer graphics, but the two most common are the RGB model (Red-Green-Blue) for computer display and the CMYK model (Cyan-Magenta-Yellow-blacK) for printing. The Two Most Common Color Models There are several established color models used in computer graphics, but the two most common are the RGB model (Red-Green-Blue) for computer display and the CMYK model (Cyan-Magenta-Yellow-blacK) for printing. RGB Color Model Additive color model For computer displays Uses light to display color Colors result from transmitted light Red+Green+Blue=White CMYK Color Model Subtractive color model For printed material Uses ink to display color Colors result from reflected light Cyan+Magenta+Yellow=Black
HA1 - Technical File – Adobe Photoshop Adobe Photoshop is a graphics editing application popular for it's extensive amount of features. Photoshop is also, currently, the leading graphics editing application. Photo shop is also an image creation software as well as an editor. Photo shop can create any effect or style needed in a drawing or painting or layout. There are graphic software that can do specialized work faster and more efficient than Photo shop (such as painter for realistic paint effects), but Photo shop can do it all in one program.
HA1 - Technical File – Adobe Illustrator Adobe® Illustrator® is computer software that enables users to design, modify and edit vector graphics images from a computer and save them as files into a number of vector graphics formats. These formats are indicated by the file extension letters after the file name. The most popular formats are Encapsulated PostScript (EPS), Portable Document Format (PDF), Windows® Metafile (WMF), Scalable Vector Graphics (SVG) and Vector Markup Language (VML). The use of mathematical equations to generate points, lines, curves and other shapes is a difference between Adobe® Illustrator® and other graphics software programs on the market. This technique is known in the jargon of the industry as "geometrical primitives" and is the basis of vector graphics.
HA1 - Technical File – Adobe InDesign Adobe InDesign is a newer version of Adobe PageMaker, a desktop publishing program. What does that mean?? Well, it means that both are tools to be used for design and layout purposes. InDesign is the perfect choice for making any document that needs some creative layout, from posters to newspapers. It offers all kinds of features to modify your text and images, which can work together in interesting ways to create a unique and professional design.