Digital Imaging Basics
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Digital imaging involves the creation, processing, compression, storage, printing and display of digital images. Key hardware considerations for digital imaging include the processor, RAM, monitor, video card, image capture device and file storage. Important software considerations are the graphics editing software, pixels, tones/levels, bit depth, color modes, resolution, and common file formats like JPEG, TIFF and PSD.
Digital Imaging Basics
- 1. computer science department – BSIT - adzu
- 2. Outline Digital Platform Pixels and Levels Resolution Vector vs. Raster Graphics Colors in Digital Imaging File Formats
- 3. What’s Digital Imaging? Digital imaging or digital image acquisition is the creation of digital images, typically from a physical object. The term is often assumed to imply or include the processing, compression, storage, printing, and display of such images.
- 4. Hardware Considerations Processor Speed RAM Size Monitor Size Video Card Image Capture Device File Storage
- 5. Monitor Considerations in choosing monitor Screen size Quality Reliability of color that the screen can display Video card Amount of Video memory
- 6. Memory RAM – Random Access Memory Graphics editing software uses 3 to 5 times the file size in RAM to function efficiently.
- 7. Processor The speed at which the computer processor can perform calculations, the number of calculations it can perform at once, the speed of data transfer as well as the number of processors within the system will all have a profound effect on the digital imaging performance.
- 8. Hard Disk Digital Imaging functions of a hard drive: Scratch Disk Space: handles the overflow “working space” which does not fit into the available RAM. Storage Space: Downloaded and manipulated files can be stored in the hard disk. Software: Hard disk stores large amount of files needed to run the software.
- 9. External Storage Redundant Array of Independent Disk (RAID) Made up of array or stack of disks and is most often found in high end systems. Enables large amount of information to be broken up into smaller segments each being stored onto a separate disk.
- 10. External Storage Magnetic Tape A.K.A. Digital Audio Tape (DAT) It has become popular as a storage for backup medium mainly due to low cost. Disadvantage: slow file searching
- 11. External Storage CD-R Writers Has become one of the cheapest storage medium available due to the decrease in the prices of CD burners and CDs.
- 12. Scanners Film Scanner Dedicated to scanning film formats from 35mm to 5x4 inches.
- 13. Scanners Flatbed Scanner The most commonly available type of scanner. Since flatbed scanners use a moving array of sensors to digitize the image, considerations of noise, dynamic range and consistency of light, need to be addressed in their design – in a similar way to that of digital cameras.
- 14. Drawing Tablet A peripheral used by graphic designers, which combines a digital tablet and an electronic pencil. It provides a high level of drawing precision.
- 15. Software Considerations Software Licensing Software features
- 16. Pixels Pixels - The small picture elements that make up a digital photograph. Pixels
- 17. Tones or Levels Levels or Tones – the brightness of a pixel 256 different levels or separate tones in a typical digital image. Continuous Tone - An image where brightness appears consistent and uninterrupted. Brightness
- 18. Bit Depth This refers to the grey scale range of an individual pixel. A pixel with 8 bits per color gives a 24 bit image (8 bits X 3 colors is 24 bits). 32768 colours 16-bit 256 shades of grey 8-bit greyscale 256 colours 8-bit 16 colours 4-bit 4 colours 2-bit black and white 1-bit Colours Available Bit Depth
- 19. Color Hue – the name of the color Saturation – the purity or strength of the color Brightness – the relative lightness or darkness of the color Brightness Hue Saturation
- 20. Resolution The fineness of detail within a predetermined size. Normally expressed as the number of pixels or dots per inch. More and smaller pixels adds detail and sharpens edges.
- 21. Output Resolution Dots per inch – defines the printing quality Interpolation – increasing the total number of pixels Resampling - The process of reducing image data set size by representing a group of pixels with a single pixel.
- 22. Vector vs. Raster Graphics Bitmap images (also known as raster images) are made up of pixels in a grid. Vector images are made up of many individual, scalable objects. These objects are defined by mathematical equations rather than pixels, so they always render at the highest quality.
- 23. Color Modes Grayscale –has 256 colors (black, white and 254 shades of gray) Bitmap – has 1 color, 100% black. This mode is suitable for printing on dot-matrix printers.
- 24. Color Modes Duotone - is similar to grayscale but replaces the black with a different color. This mode is suitable for printing with limited colors. Index - contains only a pallet of up to 256 colours. This mode is suitable for web graphics to reduce file size.
- 25. Color Modes RGB – colors are created by varying relative amounts of red, green and blue light. CMYK - stands for Cyan, Magenta, Yellow and Key. Black is just called key so that it won't be mislead for the color blue.
- 26. File Formats Most common formats: JPEG (.jpg/ .jpeg) Joint Photographic Experts Group industry standard for compressing continuous tone photographic images for the world wild web or for limited space TIFF (.tif) Tagged Image File Format Industry standard for publishing Photoshop (.psd) Photoshop Document Usually kept as a master file
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