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Ohio Memory Scanning Guidelines
All materials accepted in the Ohio Memory Online Scrapbook may be scanned at
the Ohio Historical Center. However, institutions may submit digital images
scanned elsewhere if certain technical specifications, outlined below, are met.
These guidelines also include some general scanning suggestions.
Scanning/Editing Philosophy
The general philosophy of this project is that we are scanning historical images.
The digital version should not appear significantly different than the actual
document.
- Frequently historical images have imperfections such as tears or holes,
which should not be altered or fixed.
- Do not crop the image to cut out parts of the image. You might not include
the frame or edge of the image, but you should not substantially alter the
image.
- Dirt or specks can be removed, as they are frequently only put into the
image or emphasized by the scanning process.
Technical Specifications
These specifications are taken from the OhioLINK Digital Media Center's "Scanning
Standards and Guidelines," http://www.ohiolink.edu/media/dmcinfo/metadata.html.
All scanning done for the Ohio Memory Online Scrapbook must meet these minimum
requirements, although exceptions may be made in specific cases. Please contact
Ohio Memory staff if you have any questions.
File Format and Compression
Images should be Tagged Image File Format Version 5 or 6 (TIFF 5 or 6). Bitonal
(black and white) TIFF images can be compressed using ITU Group IV compression.
Grayscale and color images can be compressed using LZW compression.
Recommended Scanning Resolutions
| Type of Original |
Minimum Resolution and Pixel Depth
|
| Published text and line art |
300 dpi (Dots perinch), bitonal |
| Illustrations |
300 dpi, bitonal or 8-bit grayscale |
| Modern type, laser-printed, archival documents |
300 dpi, bitonal (600 dpi bitonal images can be used for higher-quality
print reproductions) |
| Handwritten materials |
300 dpi, 8-bit grayscale or 24- bit color, depending on the
document |
| Stained or faded documents |
Case-by-case analysis is required |
| Maps |
300 dpi, bitonal, 8-bit grayscale, or 24-bit color |
| 35 mm negative and slide film |
Pixel dimensions of 1024x1536, 24-bit color or 8-bit grayscale.
Pixel dimensions of 2048 x 3072 can be used to create better print reproductions. |
| Photographic prints |
Requirements will vary, minimum 300 dpi, 24-bit color or 8-bit
grayscale, depending on the source. Scanning from negatives may be preferable. |
| Artwork |
When scanning photographic surrogates, such as 35-mm negative
or slide film or 4-by-5 inch transparencies, the guidelines above apply.
However, it may be better to re-photograph the work or to capture the work
with a high-end digital camera. Contact staff for more information. |
The chart above lists minimum scanning standards. In some cases it may be necessary
and desirable to scan at higher resolutions. Documents that might require scanning
at a higher resolution include those:
- with very small characters or fine print
- that are rare and/or fragile, such as a one-of-a-kind brittle manuscript
Derivative Images
Derivative images are commonly used for general web access instead of high-resolution
images. Examples include small "thumbnail" images, which might be only 100 pixels
square, and "reference" or "service" images, which should fit completely within
an average monitor. Images created for this purpose commonly are smaller in
size and load quickly, even without a fast network connection. They are generally
saved in a web-viewable format such as JPEG or GIF.
The Ohio Memory online scrapbook will include both derivative and high-resolution
image files. Derivative images will be likely the most heavily used. OhioLINK,
which will store image files for the scrapbook, has software that automatically
generates both thumbnail and service images.
General Scanning Notes
There are subjective decisions that may influence how materials should be digitized.
For instance, a black-and-white typed document may contain annotations in pencil
or red ink. Though bitonal scanning is normally sufficient for typed documents,
color scanning may be preferred in this case.
Scanners operate best when used around a consistent, fairly dim light source.
Scanning at higher resolutions does not necessarily afford additional benefits.
While the difference between 72 dpi and 600 dpi may be obvious, the same may
not be true when increasing from 600 dpi to 1200 dpi. A representative subset
of any collection should be digitized prior to production to determine whether
these guidelines provide acceptable results for intended uses, such as viewing
with monitors or printing.
Different scanners will produce different results, as will different commercial
scanning vendors. Quality control throughout a scanning project is vital.
Handling/Conservation Concerns
Fragile, rare and delicate historical materials are being scanned in this project.
Nothing should damage or jeopardize the materials during the digitization process.
Project staff designed the following rules with this concern in mind. Please
follow them to ensure the longevity of materials.
- Historical materials should be stored in a safe area, out of direct light.
Once they are to be scanned, remove items from protected area. When leaving
the scanner and materials for any length of time, be sure to place materials
out of harm's way (i.e. on cart, in folders, etc.).
- Absolutely no food or drink should be consumed near the scanners or the
materials.
- Absolutely no pens should be used near materials. Use pencils only.
- White gloves should be used whenever handling materials.
Questions: If you have any questions, please contact Ohio Memory Project staff
at ohiomemory@ohiohistory.org or (614) 297-2589.
Scanning Guidelines are also available as downloadable Word and
PDF documents.
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