User`s guide

VueScan User's Guide

Another useful way of getting multiple image samples is to scan at a higher resolution and then

average adjacent blocks of pixels. For instance, scanning at 2700 dpi and averaging every 2x2

block of pixels will result in a higher-quality 1350 dpi scan than just scanning at 1350 dpi. In this

example Scanning at 1350 dpi throws away every other pixel and every other scan line, while

scanning at 2700 dpi and settingOutput | TIFF size reduction (p. 82) to "2" will result in

averaging 2x2 blocks of pixels and increasing the number of effective bits of resolution by 2 bits.

Note that multi-scanning is the only way to increase the quality at the highest resolution, and

that using Output | TIFF size reduction (p. 82)or Output | JPEG size reduction (p. 84) is a better

way of producing quality scans at lower resolutions.

File Formats

VueScan reads raw CCD sensor data from scanners and can write this to a raw TIFF file for

later reprocessing. The final cropped data can be stored in any combination of TIFF, JPEG,

PDF and OCR text files. Index prints are stored as a Windows BMP file.

The raw and cropped TIFF files can have six different formats, each with a different number of

samples per pixel and bits per sample. A grayscale image has one sample per pixel, a normal

color image has three (red, green, blue), and scans from a scanner with an infrared channel

have four samples per pixel (red, green, blue, infrared).

VueScan internally keeps all samples in 16-bit linear format, even when a scanner only supports

10-bit samples, but to minimize the disk usage, various TIFF file formats are supported:

1 bit B/W 1 bit per pixel 1 sample per pixel 1 bit per sample

8 bit Gray 1 byte per pixel 1 sample per pixel 8 bits per sample

16 bit Gray 2 bytes per pixel 1 sample per pixel 16 bits per sample

24 bit RGB 3 bytes per pixel 3 samples per pixel 8 bits per sample

48 bit RGB 6 bytes per pixel 3 samples per pixel 16 bits per sample

64 bit RGBI 8 bytes per pixel 4 samples per pixel 16 bits per sample

16 bit Infrared 2 bytes per pixel 1 sample per pixel 16 bits per sample

If you want to process the full bit depth of an image in Photoshop(TM), use the 48 bit RGB

setting for the Crop TIFF file. Note that some other image editing tools cannot process 48 bit

TIFF files; in this case use 24 bit which is more widely compatible.

Note that the raw scan files are stored in linear format when using more than 8 bits per sample,

and stored in gamma 2.2 format when using only 8 bits per sample. The saved TIFF files are

always gamma corrected according to theColor | Output color space (p. 75)used (1.8 for Apple

RGB, ColorMatch RGB, ProPhoto RGB and ECI RGB and 2.2 for all other color spaces). Note

that the raw scan files stored in linear format will look dark when viewed - this is normal.

Note that both the raw TIFF file and the crop TIFF file can be compressed. VueScan uses

CCITT Group-IV compression for 1-bit files, and LZW compression otherwise. This may be

slower to write, but takes around 40% less disk space. The size of JPEG files can be controlled

with the Output | JPEG quality (p. 84)option, with useful values ranging from 75 (very

compressed, medium quality) to 95 (less compression, high quality).

Film types