EPM Tech Tip 089: Density Range for the Kodak Archive Writer

This Eastman Park Micrographics (EPM) guide explains why the background density range for film written with the Archive Writer follows source document guidance (ANSI/AIIM MS 23) rather than the range for COM films.

Highlights

• The recommended range for film writers under Tech Tip 76 is 0.90 to 1.10.
• Information is in the low-density lines, not the background, but because measuring line density is not practical, background density is controlled with macro densitometry.
• The accepted range of 0.80 to 1.20 comes from ANSI/AIIM MS 23 - 1998 for optical filming of business documents.
• For COM films with reversal processing, ANSI/AIIM MS 1 - 1996 specifies a minimum Dmax of 1.5 (preferably 1.8) and a maximum Dmin of 0.2.
• IMAGELINK Archive Writer media is designed to emulate a source document system, not COM.
• For the EPM Document Archive Writer 4800 and IMAGELINK i9600 Series the optimum range is 0.90 to 1.0, and allowing for device and processing variation, 0.85 to 1.15 is acceptable.
• Resolution expectations should be based on requirements for digital devices such as ISO 14648-1:2001.

Description

The capture method, whether traditional or digital, has no significant effect on image legibility. In the Archive Writer, the scanner converts the document into a bi-tonal image, so differences in document reflectance are removed and background density results solely from all pixels being on. For this reason the system can control background density more precisely than the general guidance.

A single background density cannot be specified for all digital writing systems; the value depends on the imaging components and the contrast and density range of the media, and the variety of light sources such as laser, LED, CRT and eBeam leads to a variety of media.