User`s guide

VueScan User's Guide

VueScan does two different things: it scans an image, and then it processes the raw data from

the scanner to produce a color-corrected image. These two things are done in steps, and it's

useful to understand each of the steps when scanning and processing.

The Preview button (p. 46) and Scan button (p. 47) perform both the scanning and processing

steps. The Save button (p. 48) starts from the raw CCD data in memory and only performs the

processing step.

Scanning

Scanning an image involves: optionally focusing the scanner, setting up the exposure time for

the CCD area to be scanned, number of bits per sample, number of samples per pixel, scan

resolution, and then reading the raw CCD data into VueScan's memory buffer.

If single-pass multi-scanning is enabled, each line of data from the CCD is read multiple times

and combined (averaged) while being stored in the memory buffer. If multi-pass multi-scanning

is enabled, the whole scan area is read multiple times and combined (averaged) in the memory

buffer.

There is no scaling or color correction of the raw CCD data in the scanning step. Some

scanners either always or sometimes convert 10-bit or 12-bit CCD data to 8 bits before

transferring it to VueScan, and then VueScan converts it back to 10-bit or 12-bit CCD data. This

is done using the same gamma correction table specified by the sRGB standard.

When the Input | Source (p. 50) option is set to "File", the raw CCD data is read from a TIFF or

JPEG file and stored in the memory buffer, just as if it had been read directly from a scanner.

When the preview image is scanned, the exposure time is fixed at 1.0, the area to be scanned is

the full preview area, and the scan resolution is set to a value that produces approximately 1

million pixels.

When the full scan is done, the exposure time is either computed from the preview or from the

manual setting and the area to be scanned is a subset of the preview area (determined by the

cropping). If the scan resolution is Auto, a scan resolution is chosen that produces

approximately 4 million pixels.