ENCAD 215319-1 User Manual page 16

5. Post Scanning Color Correction and Sharpening
All scanned images, even those scanned on expensive drum scanners, must be color
corrected and sharpened before using them for a large-format inkjet print. If you are
using a service bureau for scanning images, their scanner operator will usually do this as
part of the scanning fee. However, you should always check the image before using it.
Although the process of color correction and sharpening are more detailed than can be
explained within this document, the following outline will give you a good grasp of
what is required:
Color Correction - all scanners give the image a slight color cast during the scanning
process. This happens because all light sensing devices have a slight bias. The easiest
way to correct most of this color cast is to use a function such as Auto Levels in
PhotoShop. This function finds the whitest pixel and the darkest pixel in an image and
distributes all colors in-between. This works well on 75% of all images that are properly
exposed. In very dark night scenes or in very white snow background scenes, Auto
Levels does not work properly and the correction must be made manually using histo-
gram adjustments.
Sharpening using UnSharp Mask - all scanned images, even images scanned on the
most expensive drum scanners, need to be sharpened. The best digital tool to do this
with is a function called an unsharp mask (available in programs such as PhotoShop).
An unsharp mask basically redefines the edges of images by adding a mask. Most
unsharp mask tools allow you to set the pixel width of the mask and the amount of
sharpening. A good start is to use a pixel width of 3 - 5, with an amount of 75%. Too
much unsharp mask will give the whole image a hard, pixelated look. A little more
unsharp mask can be used with inkjet images as they are somewhat diffused in the
printing process, hiding any small amounts of oversharpening.
6. RIP Color Profile
The engine that converts your image into a series of C, M, Y, K dots is called the Raster
Image Processor or RIP. Before it can actually create these dot patterns, it must first
adjust for the colors of the inks, color of the media, dot volume of the cartridges on a
particular machine, and the humidity/temperature of the environment on the day of
printing (as this affects how far the ink will spread or dot gain). Most RIPs include what
is commonly referred to as a color profile or color link. This profile is automatically used
when you choose the media and ink within the software.
CADJET ® 3D User Guide
Introduction 1-7