Contents

Understanding Image Histograms and Curves

Histograms

Image Histograms

Color Channels

Histograms and Pixel Structure

Local Histograms

Using Histograms as a Scanner Tool

Prescan Histograms

Postscan Histograms

Evaluating Histogram Area

Image Exposure and Tone Curves

The Scanning Process

Changing Brightness and Contrast

Color Corrections

Examples

Summary

Interactive Demos

Setting Exposure

Setting Image Curves

Appendices

The Photoshop Levels Function and Curves

Why Is There No Luminosity Tool?

Average Skin Tone

Using Histograms to Track Scanner Performance

Further Information

Order Hardcopy Version

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High-Performance Scanners Are Not Immune from Grain

Since grain visibility is a characteristic of the film type and not the scanner, even high-end scanners exhibit grain.  In fact grain is even more pronounced because of the higher true resolution and dynamic range of professional scanners.

This sailboat image was produced on a $55,000 flatbed scanner.  The next image is a full-size detail from the scan which has been color balanced but not sharpened.

Although the scan was performed at a relatively low resolution, the grain is clearly visible because of the crispness of detail that this scanner is capable of delivering.

The next image was scanned on a popular medium-format film scanner at the same resolution:

This image, also, was color balanced but not sharpened.

Why Grain Is Such a Pain

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