(a) Agencies must apply the standards in this section when microfilming:
(1) Permanent paper records where the original paper record will be destroyed (only after authorization from NARA);
(2) Unscheduled paper records where the original paper record will be destroyed (only after authorization from NARA); and
(3) Permanent and unscheduled original microform records (no paper originals) produced by automation, such as COM.
(b) Agencies must use polyester-based silver gelatin type film that conforms to ISO 18901 (incorporated by reference, see § 1238.5) for LE 500 film in all applications.
(c) Agencies must process microforms so that the residual thiosulfate ion concentration will not exceed 0.014 grams per square meter in accordance with ISO 18901 (incorporated by reference, see § 1238.5) and use the processing procedures in ANSI/AIIM MS1 and ANSI/AIIM MS23 (both incorporated by reference, see § 1238.5).
(d) Agencies must use the following standards for quality:
(1) Resolution -
(i) Source documents. Agencies must determine minimum resolution on microforms of source documents using the method in the Quality Index Method for determining resolution and anticipated losses when duplicating, as described in ANSI/AIIM MS23 and ANSI/AIIM MS43 (both incorporated by reference, see § 1238.5). Agencies must perform resolution tests using an ANSI/ISO 3334 Resolution Test Chart (incorporated by reference, see § 1238.5) or a commercially available certifiable target manufactured to comply with this standard, and read the patterns following the instructions of ANSI/ISO 3334. Agencies must use the smallest character used to display information to determine the height used in the Quality Index formula. Agencies must use a Quality Index of five at the third generation level.
(ii) COM. COM must meet the requirements of ANSI/AIIM MS1 (incorporated by reference, see § 1238.5).
(2) Background density of images. Agencies must use the background ISO standard visual diffuse transmission density on microforms appropriate to the type of documents being filmed. Agencies must use the procedure for density measurement described in ANSI/AIIM MS23 (incorporated by reference, see § 1238.5). The densitometer must meet with ANSI/NAPM IT2.18 (incorporated by reference, see § 1238.5) for spectral conditions and ANSI/NAPM IT2.19 (incorporated by reference, see § 1238.5) for geometric conditions for transmission density.
(i) Recommended visual diffuse transmission background densities for images of documents are as follows:
| Classification | Description of document | Background density |
|---|---|---|
| Group 1 | High-quality, high contrast printed book, periodicals, and black typing | 1.3-1.5 |
| Group 2 | Fine-line originals, black opaque pencil writing, and documents with small high contrast printing | 1.15-1.4 |
| Group 3 | Pencil and ink drawings, faded printing, and very small printing, such as footnotes at the bottom of a printed page | 1.0-1.2 |
| Group 4 | Low-contrast manuscripts and drawing, graph paper with pale, fine-colored lines; letters typed with a worn ribbon; and poorly printed, faint documents | 0.8-1.0 |
| Group 5 | Poor-contrast documents (special exception). | 0.7-0.85 |
(ii) Recommended visual diffuse transmission densities for computer generated images are as follows:
| Film type | Process | Density measurement method | Min. Dmax1 | Max. Dmin1 | Minimum density difference |
|---|---|---|---|---|---|
| Silver gelatin | Conventional | Printing or diffuse | 0.75 | 0.15 | 0.60 |
| Silver gelatin | Full reversal | Printing | 1.50 | 0.20 | 1.30 |
(3) Base plus fog density of microfilms. The base plus fog density of unexposed, processed microfilms must not exceed 0.10. When a tinted base film is used, the density will be increased. The difference must be added to the values given in the tables in paragraph (d)(2) of this section.
(4) Line or stroke width. Due to optical limitations in most micrographic systems, microfilm images of thin lines appearing in the source documents will tend to fill in as a function of their width and density. Therefore, as the reduction ratio of a given system is increased, reduce the background density as needed to ensure that the copies will be legible.