5 CHALLANGES in Scanning Contones & Working with Digital Images
1. Changes in Image
• Digitalization
• Flattens/softens an image
• Contrast of tones change
• Scan-View-Print differences
2. Loss of data - up to 95% color information
• The eye sees over 5000 different tones
• Films sees 1000 different tones
• Digital records 256 different grays (p/pix)
• Print records only from 80 to 120 value grades
• Tonal compression every time you size
3. Dynamic Range Shift in Shadows
• Densities darken in shadow areas
• Watch for total ink/toner coverage limits
4. Media Change- dot gain in midrange tones
• Depends on ink and paper
• glossy paper - 5% dot gain
• newsprint - 30% dot gain
• digital - toner can spread slightly on drum or “sprinkle”
• Check value scale with your printer
5. Gamut Conversions for different media output
• RGB - Original scanning, Electronic media
• INDEX colors - Video/Web images
• CYMK - Printing for process - oil, die and diazo based
• BEYOND GAMUT - PMS, Toyo, Metallic, Dayglo,
• Tinted Varnishes, Soy inks, Watercolor inks
5 RULES in Scanning Contones and Working with Digital Images
1. Know what output you want & scan for that
resolution (& line-screen) requirement:
Web no line sceen .............. 72 dpi max
Laser 65 to 95 lpi .................. 150 dpi max
Newspaper 85 to 95 lpi .................. 150 to 180 dpi max
Brochures 133 to 150 lpi .............. 200 to 300 dpi max
high-end bks 175 to 200 lpi .............. 300 to 400 dpi max
line art no line screen ............ 600 to 1,200 dpi max
InkJet hi-fi/stochastic ............ 300 to 400 dpi
2. Try to always scan at the desired size
If you have to, scan larger and reduce 10%
3. Try to always manipulate the image in Photoshop BEFORE placing the image in a
page-layout or other Document.
SHARPEN the image in photoshop as the LAST
thing you do after adjusting for color and value.
4. Scan & adjust in RGB
CONVERT TO CYMK for printing -
Ask your printer WHEN to convert to CYMK. If the printer is going to color manage, then package your images in RGB.
MOST home laser printers print better in RGB and some commercial digital printers now require RGB.
5. SAVE the image for the desired output media:
For InDesign/QuarkX ....................save images as a.psd (Photoshop) or TIF
In Illustrator page layout ................save images as an .ai (Illustrator) or EPS
For powerpoint/mm/PS Slides .......save as PICTS
For contone images on web ..........save as JPEG
For graphics/charts/type on web ...save as GIFS |