Eddie Tapp - Practical Color Management: Eddie Tapp on Digital Photography

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calibrate and profile devices

calibrating

profiling

CMYK

color-managed workflow

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Epson 4800 printer

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gamma

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ICC profiles vii

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output

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Photoshop

printers

projectors

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RGB

RIPs (Raster Image Processors)

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scanners

scanning

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technical aspects of color management

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UPDIG refers to the Universal Photographic Digital Imaging Guidelines, a set of best practices for digital photography that have been put together by a group of working photographers, manufacturers, and trade groups. Included here are some UPDIG excerpts that are relevant to color management.

The following is an excerpt from the guidelines available at http://www. updig.org. Used with permission.

• Digital images look the same as they transfer between devices, platforms, and vendors.

• Digital images are prepared in the correct resolution, at the correct size, on the devices(s) on which they will be viewed or printed.

• Formats and names . File formats should always be denoted by standard, three-letter file extensions.

  1. For the Web, use JPEG files.

  2. For print, uncompressed TIFFs are best. Use JPEG only when bandwidth or storage constraints require it. Use the highest JPEG quality setting possible. We recommend not using less than "8" quality.

  To avoid problems with files that will be transferred across computing platforms, name files with only the letters of the alphabet and the numerals 0 through 9. Avoid punctuation marks (other than hyphen and underscore), accented vowels, and other special characters. Keep the full name (including extension) to 31 characters or less for files on a network or removable media and to 11 characters or less (including the three-letter file extension) when burning to CD-R, in case a recipient's computers don't support long filenames. For the complete guide to file naming protocol, see the Controlled Vocabulary website (http://www.controlledvocabulary.com/imagedatabases/filename_limits.html).

• Appropriate resolution . Resolution of digital images is described by three numbers: height, width, and ppi (pixels per inch). Beware: it's easy to confuse ppi with dpi (dots per inch), which refers to the resolution of a printing device, or with lpi (lines per inch), which describes a halftone grid or screen used for printing images on a press.

  The following target resolutions are meaningful only when paired with the height and width at which an image will appear in the final form:

  1. Low (monitor or "screen") resolution is defined as less than 100 ppi.

  2. Ink-jet prints normally need resolutions of 180360 ppi.

  3. Continuous-tone printing requires resolutions of 250400 ppi.

  4. The offset-printing standard is often considered 300 ppi. But resolutions of 1.32 times the halftone screen for the project are considered safe. If the images will be printed at 150 lpi, the appropriate image file resolution range would be 195300 ppi.

• Sharpen last . All digital images require sharpening, during capture or after, and the correct amount to apply depends on the type of use and size of the final output. For most uses, it's best to sharpen little or none during capture with a camera or scanner. Sharpening is an art, and requires study and practice. There are several schools of thought regarding proper sharpening. One recommended method is to remove capture softness using a gentle sharpening pass followed by local sharpening and/or output sharpening. Sharpening should be the final step in reproduction, because resizing and contrast adjustment affect an image's sharpness. Sharpening is best evaluated at 100 percent and 50 percent views on your monitor, or by making a print. The most common sharpening method is to apply an "unsharp mask" filter (higher settings for higher-resolution files) to images, but other sharpening methods and Photoshop plug-in programs can be useful, too. Oversharpening creates obvious halos around edges within images.