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  1. 1. PixelsIn digital imaging, a pixel, or pel, (pictureelement) is a physical point in a raster image, orthe smallest addressable element in a displaydevice; so it is the smallest controllable elementof a picture represented on the screen
  2. 2. A pixel is generally thought of as the smallest single component of a digitalimage. However, the definition is highly context-sensitive. For example, therecan be "printed pixels" in a page, or pixels carried by electronic signals, orrepresented by digital values, or pixels on a display device, or pixels in a digitalcamera (photo sensor elements).Graphics monitors display pictures by dividing the display screen intothousands (or millions) of pixels, arranged in rows and columns. The pixels areso close together that they appear connected.
  3. 3. Pixel colour depthColour depth is defined by how many bits per pixel can be displayed on screen at one time. Eachbit Represents 2 colours because it has a value of either 0 or 1. So basically the More bits to Eachpixel the more amount of colours or shades of one colour can be displayed.For example:The number of bits used to represent each pixel determines how many colours or shades of greycan be displayed. in 8-bit colour mode, the colour monitor uses 8 bits for each pixel, making itpossible to display 2 to the 8th power (256) different colours or shades of grey.Below are some examples of colours Shown By using a different amount of bits for each pixel: bit 4 bits 24 bits (truecolour)
  4. 4. Light Converting – CamerasInstead of using film, digital Cameras use a special Silicone Sensor To convertlight into a electrical charges and then a digital image. These Sensors havemillions of ‘’photosites’’ on them (often called pixels) that are sensitive tolight.
  5. 5. ResolutionResolution means How sharp an image is and is most often used in Monitorsand Bit-mapped Graphic image.Bitmapped images are Composed of pixels, Resolution is the number of pixelsper inch of the image (ppi)Two Aspects of a Bitmapped image that Determine the number of pixels in anare The size (width and height in inches) and the Resolution ( the amount ofpixels per inch)The more pixels that are in an image the more Detail can be displayedproperly. The few the pixels the less detail.
  6. 6. Screen RatioIt is commonly expressed as two numbers separated by a colon, as in 16:9. For anx:y aspect ratio, no matter how big or small the image is, if the width is dividedinto x units of equal length and the height is measured using this same lengthunit, the height will be measured to be y units. For example, consider a group ofimages, all with an aspect ratio of 16:9. One image is 16 inches wide and 9 incheshigh. Another image is 16 centimetres wide and 9 centimetres high. A third is 8yards wide and 4.5 yards high.The most common aspect ratios used today in the presentation of films in movietheatres are 1.85:1 and 2.39:1.Two common videographic aspect ratios are 4:3(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.Other cinema and video aspect ratios exist, but are used infrequently.
  7. 7. Frame RateThe frame-rate says how many images of a movie aredisplayed every second a movie is played.The higher frame rate a movie has the smoother objectsmove in the movie.Compare a movie with low frame rate with a movie withhigher frame rate. The movie with high frame has moreframes for the same number of seconds film. The moviewith higher frame rate will also be stored in a larger file.You measure frame rate in frames per seconds (fps).Frame rate in game is the same thing. The only differencebetween movie frames and game frames are that movieframes are created as you play for a movie they are justrecreated from a file.A constant frame rate is desired for smooth playback.Depending on the compression used in the video file it canput a heavy load on your computer. If the computer is notable to replay the movie at the frame rate it was encodedfor it will either stutter and slowdown or drop frames will bedropped.
  8. 8. Video Formats and compressionA video format defines the way in which a video is recorded and stored.It normally specifiesCode/compressionFrame RateFrame sizeFrame Aspect RatioPixel Aspect RatioScanning Method.Common formats are DV, HDV and AVCHD.Compression is The way that date is encoded into the file andDecoded when played back. There are two Types of Codec(compressor) A lossy codec or a lossless codec. A lossy codec willThrow away data and the final video will be of less quality but with asmaller file size Whereas a lossless codec will keep all data and willResult in a higher quality final video but with a much larger file sizeAdvanced Coding High Definition(developed by sony and Panasonic in 2006)Launched in 1995 for storingdigital videoHDV is a format for recording of high-definition videoon DV cassette tape. The format was originallydeveloped by JVC and supported by Sony, Canon andSharp. The four companies formed the HDVconsortium in September 2003.