Glossary

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Glossary

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Glossary

  1. 1. Pixel- In digital imaging a pixel is a physical point in a raster image or thesmallest addressable element in a display device so it is the smallestcontrollable element of a picture represented on the screen. The address of apixel corresponds to its physical coordinates.The term pixel is actually short forPicture Element.These small little dots are what make up the images on digital.The screen is divided up into a matrix of thousands or even millions ofpixels.Each pixel can only be one colour at a time. However, since they are sosmall, pixels often blend together to form various shades and blends ofcolours. The number of colours each pixel can be is determined by the numberof bits used to represent it.Resolution - Refers to the sharpness and clarity of an image. Theterm is most often used to describe monitors, printers, and bit-mapped graphicimages.Bitmap images are composed of pixels. Image resolution is simply thenumber of Pixels Per Inch (PPI)in the bitmap grid.There are two aspects toevery bitmap image - its size(width and height in inches) and resolution(thenumber of pixels per inch). These two factors alone determine the totalnumber of pixels in an image. Some of the typical resolutions include;256x256- Found on very cheap cameras, this resolution is so low that thepicture quality is almost always unacceptable. This is 65,000 total pixels.640x480 - This is the low end on most "real" cameras. This resolution is idealfor e-mailing pictures or posting pictures on a Web site. 4064x2704 - A top-of-the-line digital camera with 11.1 megapixels takes pictures at this resolution.At this setting, you can create 13.5x9 inch prints with no loss of picture quality.The more pixels there are in an image, the more detail the image can bedisplayed with. The fewer pixels there are in an image, the less detail theimage can be displayed with. There are two ways to display an image - onscreen and in print. The standard for screen displays is 72 PPI.The standard forPrint is 300 PPI.
  2. 2. Screen Ratios - The aspect ratio of a screen or image describesthe proportional relationship between its width and its height.It is commonlyexpressed as two numbers separated by a colon, as in 4:3 and 16:9. The mostcommon aspect ratios used today in the presentation of films in movietheatres are 1.85:1 and 2.39:1. Two common video aspect ratios are4:3(1.33:1), the universal video format of the 20th century. And 16:9 (1.77:1),universal for high-definition television and European digital television.In stillcamera photography, the most common aspect ratios are 4:3, 3:2, and morerecently being found in consumer cameras 16:9. This is important as manyDSLRs are being used to shoot video due to the quality of their internal sensorsand superior lenses. With television, DVD and Blu-ray Disc, converting formatsof unequal ratios is achieved by enlarging the original image to fill the receivingformats display area and cutting off any excess picture information (zoomingand cropping). By adding horizontal mattes (letterboxing) or vertical mattes(pillarboxing)to retain the original formats aspect ratio.Pixel Aspect Ratio describes the relationship between the width and height ofa single pixel.Different pixel aspect ratios are the reason why two video imageswith identical frame sizes can appear as different sizes on screen.If width =height, then the pixel is square and the aspect ratio (width÷height) = 1.0.Frame Rate - The human eye and its brain interface, the humanvisual system, can process 10 to 12 separate images per second, perceivingthem individually. Early silent films had a frame rate from 14 to 24 FPS whichwas enough for the sense of motion, but it was perceived as jerkymotion.Persistence of vision was a commonly-accepted although somewhatcontroversial theory which states that the human eye always retains imagesfor a fraction of a second on the retina (around 0.04 second).
  3. 3. Frame Rate tells you how many frames per second there are when recording orplaying video/dvd. Video cameras in Europe use 25 frames per second (fps). InUSA & Japan 29.97fps or 30fps is used.Animation works by recording eachframe individually (e.g. with a stills camera) and then playing them back at aframe rate. They also often work with a lower frame rate (e.g. 12fps) so lessframes are needed for the same length video clip.Frame rate is most oftenexpressed in frames per second (FPS) and is also expressed in progressive scanmonitors as hertz (Hz).Video Formats–A video format defines the way in which video isrecorded and stored. It normally specifies: Codec/Compressor, Frame Rate,Frame Size, Frame Aspect Ratio, Pixel Aspect Ratio, Scanning Method. Somecommon formats are DV, HDV, AVCHD. Tape based formats such as DV andHDV can be transferred to a computer for editing via firewire. File basedformats such as AVCHD are already stored as files and can be transferred to acomputer for editing via USB or card reader. File-based formats may need tobe converted during or after transfer to compatible with editing software.Compression–Codec is short for coder-decoder and describes themethod in which video data is encoded into a file and decoded when the file isplayed back. Most video is compressed during encoding, and so the termscodec and compressor are often used interchangeably.

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