Canon CanoScan FS2700F User Guide - Page 48

STEP 4 Color Correction - Histogram Setting The data comprising an image contains a variety of brightness settings ranging from shadows to highlights. These settings are represented in Plug-in module FS by values ranging between 0 and 255. You can use the histogram to adjust the values assigned to particular dot to either 0 or 255, to change the distribution of brightness settings and to control the contrast. The method is applicable to 8-bit grayscale, 12-bit grayscale, 24-bit color (when ColorSync™ is off) and 36-bit color images. How to Interpret Histograms You can select the entire image or specify an area for which a histogram will be generated. The height of the peaks of the histogram is directly related to the volume of data with the corresponding value. Portion with Highlights Distribution of data with a bias toward highlights. Portion with Shadows Distribution of data with a bias toward shadows. Entire Image Shadow (Level 0) Distribution of data widely distributed between shadows and highlights. Highlight (Level 255) How to Adjust Histograms To change the contrast in an image, the distribution of data between shadows and highlights can be adjusted by dragging the shadow and highlight marks at the bottom of the histogram. All of the data lying to the outside (left) of the shadow mark is changed to a zero value and all of the data lying to the outside (right) of the highlight mark is changed to a 255 value. The examples below show adjustments to improve the contrast. Leave the setting on Auto Correction for histogram correction of most scanning jobs. IMAGE Image with a bias 1 toward highlights IMAGE Image with a bias 2 toward shadow IMAGE Image with well 3 distributed data Move the shadow mark toward the highlight end. 48 Move the highlight mark toward Move both the shadow and the shadow end. highlight marks inward. 48