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Digital Darkroom I

Digital Darkroom I. Theresa L. Ford. Objectives. Basic Digital Image Terminology Screen Display of Pictures Why are pictures too big for the screen? Why can’t I send/receive a picture over email? Software Demos. Hardware Requirements.

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Digital Darkroom I

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  1. Digital Darkroom I Theresa L. Ford

  2. Objectives • Basic Digital Image Terminology • Screen Display of Pictures • Why are pictures too big for the screen? • Why can’t I send/receive a picture over email? • Software Demos

  3. Hardware Requirements • Add RAM memory - the larger the file size you are working with, the more you need. • Adobe Photoshop CS2 requires a Pentium 3 or 4 equivalent processor, 320 Mb of RAM, 650 Mb of disk space, 1024x768 monitor resolution with a 16 bit video card. That’s techie for “if the computer is over 2 years old, you’ll likely have problems”.

  4. Getting a Digital Image • Scanner • For printing, scan at highest resolution. • Digital Camera • For the best print options, set the camera to save the largest file size (maximum resolution). • Unfortunately, this means you can’t take as many pictures per disk.

  5. What is a Digital Image? • Tiny squares of color called dots or pixels saved as data in computer files.

  6. Describing a Digital Image • File Type - how the pixel data is stored • Image Size - width and height in pixels • File Size - space used to store data in bytes • Color Depth - how many colors • Color Space - which colors • “Resolution” - ?

  7. File Types • RAW - Camera sensor data, stored in a vendor specific format • Canon RAW is not the same as Nikon RAW • Requires special support in picture editing programs • TIF/TIFF - Tagged Image File Format • Many file variations to handle many options • Typically used for lossless image data storage • JPG/JPEG - Joint Photographic Experts Group • Lossy compression creates smaller file sizes • GIF, BMP, PICT, PNG

  8. Image Size

  9. Resolution ? • Total number of pixels - approximately - from the camera specs (2.1 megapixels) • Image size - pixel width by pixel height (800x600) • Pixel density - pixels per inch (PPI) (72 PPI) • Printer ink drop density - dots per inch (DPI) (2880 x 1440 DPI) • Display setting on monitor - pixel width by pixel height (1024x768)

  10. More Definitions of Resolution • Color depth - number of available colors on the monitor (4294967295 - 32 bit - true color) • Number of available colors in the image file (8 bit/16 bit) • What you intend to do in 2006

  11. DPI and PPI • Often used interchangeably (though inaccurately). • DPI usually refers to printers - the more dots of ink (CMYK) per inch, the better the print quality. • PPI usually refers to the viewed image size (print) - the number of pixels or dots in a displayed inch. • A computer screen displays 72 pixels per inch at 100%. • A 800x600 (pixel width by pixel height) image can be saved with any PPI.

  12. File Size and the Internet • Most email clients block attachments over 2Mb. • 2Mb takes a long time to download over 56Kb (modem). • A 4”x6” print scanned at 584 PPI is 5Mb. For happiest internet file sharing, crush the file to it’s smallest size with acceptable image quality.

  13. Optimizing for the Web • Step 1 - Copy files (never work with originals) • Step 2 - Edit composition (if you must) • Step 3 - Shrink to desired image size • Step 4 - Sharpen • Step 5 - Shrink to the smallest file size without losing quality

  14. Some Graphics Software • Photoshop CS • The Gimp • Paint Shop Pro • XAT.com’s optimizers • ImageMagick • Picasa • Irfanview

  15. A Little Math • Pixels / PPI = Print Size at 100% • Pixels / 72 = Screen Size at 100% For best print quality, use the highest PPI possible to a maximum of the printer’s ability.

  16. A Little More Math • To make an 8”x10” print at 300 PPI: • 8” x 300 PPI = 2400 Pixels • 10” x 300 PPI = 3000 Pixels • To make a 800x600 Desktop Background: • 800 Pixels • 600 Pixels • PPI is irrelevant

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