Light Inc.12200 Tech Road,
Silver Spring, MD 20904
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SCANNING IMAGES
FOR POSTERS: All scans or digital images submitted must be RGB. CMYK images will be converted which will result in a color shift. For scanned images, large format printers can only print 1/4 (one-fourth) their maximum resolution. We use 600 dpi Large Fromat Printers, therefore, for the best quality, images should be scanned at 150 dpi at the final print size. We have found that 75 dpi will also create an excelent image.
Assuming you are scanning a full 4"x6" photograph and you are creating an 8"x12" image on the poster, you should scan your photo at 150 dpi. When enlarged 2x for printing the result will be our minimum of 75 dpi.
If you are only scanning 1/2 the image area (approximately 2"x3"), you should scan your image at 300 dpi.
As the poster size increases, the scan resolution should increase proportionately.
Save your scanned images as RGB UNCOMPRESSED TIFF files.
GENERAL SCANNING INSTRUCTIONS:
Scan resolution is determined by the device it will be displayed or printed
on and the final output size. For example: Lets assume you have a 2x4 inch photo
that you would like to print in a 3x6 inch window on a printed document and
on slide film. First you must determine what resolution the output device can
print or display. A 600 dpi (dots per inch) color printer can only resolve a
150 dpi (600 / 4 = 150) because one dot (pixel) is used for each color. In our
example we will be printing our image one and one-half times it's original size.
We know we can only resolve 150 dpi on the printer, therefore,
target dpi x magnification = scanner dpi
150 x 1.5 = 225 dpi
Since we also want to print this image on film, our 4k RGB film recorder can resolve
4096 pixels across x 2732 pixels high on it's tube. Film recorders combine all
three colors on a single pixel to mix colors, therefore, 1:1 resolution can be
resolved. We will assume that the document size is 7.33x11. To determine how many
pixels we have per inch, we divide 4096 / 11 which equals 372dpi. Using the formula
from above:372 x 1.5 = 558 dpi
As you can see from the examples, the same image requires a different amount of data depending on it's final use. The file size for the printer will be approximately 2k and for film will be about 4.5k. An image scanned to fill an entire slide would require over 11mb of data. Note: Our experience has shown that ½ the above resolution is adequate for 35mm slide purposes.
The following is the MAXIMUM usable dpi for the most common devices:
DPI
TARGET Color B&W
WEB PAGES 72 72
300 DPI printer 75 300
600 DPI printer 150 600
4k 35mm slides 180 180
8k 35mm slides 360 360
Remember that one-half the above resolution will normally work just fine.
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12200 Tech Road, Silver Spring, Maryland 20904
(301) 680-9700 FAX: (301) 680-0575
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