Digital Content Creation

 


 

Digital Content Creation

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3.0 Best Practices for Creating Digital Images

Download PDF for Chapter 3

Introduction

This section describes best practices for digitization of print based original documents including photographs, manuscripts, maps, and text.  These guidelines draw heavily on previously published standards and best practices developed by standards agencies and peer institutions, particularly those of the California Digital Library.  Best practices for newspaper digitization are covered in Section 5.  Best practices for intellectual property rights (IPR) issues, which should be investigated before scanning materials and making them publicly accessible, are covered in Section 15.

Table of Contents

3.1 Types of files produced

3.2 Minimum master image quality requirements

3.3 Minimum image quality requirements for digital access and thumbnail image files

3.4 Additional resources

 

 

 

 

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3.1 Types of files produced

At a minimum, digitization of library materials should result in the creation of a master (archival) image and at least one access derivative for web display.  Depending on the format of the material and its anticipated use and display, other files, such as thumbnails, PDFs, and OCR text files, may also be produced.  Files should be named in accordance to the best practices for file naming in Section xx of this document. As they are produced, files should be saved to a workspace that resides on a Library server that is backed up nightly. 

Master (archival) files

The source files for all other digital files and ensure the long-term usability of the digital information.  A digital master file may serve as a surrogate for the original, may completely replace originals, or may be used as security against possible loss of originals due to disaster, theft and/or deterioration. Images are captured at a quality high enough to serve these potential uses via scanning or digital photography, depending on the attributes of the original. The digital master file should represent as accurately as possible the visual information in the original object.  In general, decisions about image capture should err towards the highest quality. Files should use color rather than grayscale when color is an integral attribute of the original, and any compression applied to the file should be lossless.  Accuracy and consistency in tone and color reproduction through appropriate use of scanner or camera controls is the goal;

Access files

Derived from master files and are used for presentation and transmission over networks.  These images should be of good quality, but because their spatial resolution (measured in pixels per inch) is lower, the file size is smaller. Some minor post-scan adjustments to optimize image quality and to bring all images to a common rendition are acceptable. Such adjustments include the use of appropriate image processing tools to achieve final color balance and tone distribution and to sharpen scanned images to match appearance of the originals.

Very small files used in databases or web pages. Clicking on the thumbnail image will pull up the larger original image, which can be viewed and downloaded.

Thumbnail files

Are very small files used in databases or web pages. Clicking on the thumbnail image will pull up the larger original image, which can be viewed and downloaded.

 

Additional files for textual materials:

3.2 Minimum image quality requirements for digital masters

 

The imaging quality requirements for master digital images are given below.  These requirements should be viewed as the minimum necessary to create quality digital images and may be exceeded when warranted and when storage space permits.  Associate technical metadata should be saved to the header file.

 

Textual Documents, Graphic Illustrations/Artwork, Maps, and Plans

For Clear, High-Contrast Documents With Printed Type (e.g., Laser Printed or Typeset):

File format:

Pixel array:

Resolution and bit depth:

or


For Documents With Poor Legibility or Diffuse Characters (e.g., Carbon Copies, Thermofax/Verifax), Handwritten Annotations or Other Markings, Low Inherent Contrast, Staining, Facing, Halftone Illustrations, or Photographs:

File format:

Pixel array:

Resolution and bit-depth:

For Documents As Described For Grayscale Scanning and/or where color is important to the interpretation of the information or content, or desire to produce the most accurate representation:

File format:

Pixel array:

Resolution and bit depth:


Photographs: Transmissive Originals (Film, Slides, and Negatives)

For Originals With 35 mm and medium format, up to 4 x 5 in.; Size Range Smaller Than 20 sq. in.:

File format:

Pixel array:

Resolution:

Bit depth:

or

For Originals With Format Range Equal to or Larger Than 4 x 5 in. and Up To  to 8 x 10 in.; Size Range Equal To or Larger Than 20 Square in and Up To 80 Square In.:

File format:

Pixel array:

Resolution:

Bit depth:

or

For Originals With Format Range Equal To or Larger Than 8 x 10 in.; Size Range Equal To or Larger Than 80 sq in:

File format:

Pixel array:

Resolution:

Bit depth:

or

Photographs: Reflective Originals (Prints)

For Originals With Format Range 8x10 in or Smaller: Size Range Smaller Than or Equal To 80 Square in.:

File format:

Pixel array:

Resolution:

Bit depth:

or


For Originals With Format Range Equal To or Larger Than 8x10 in. and Up To 11x14 in.; Size Range Equal to or Larger Than 80 Square Inches and Up To 154 Square in.:

File format:

Pixel array:

Resolution:

Bit depth:

or

For Originals With Format Equal To or Larger Than 11x14 in. Size Range Equal To or Larger Than 154 Square in.:

File format:

Pixel array:

Resolution:

Bit depth:

or


Aerials: Transmissive Originals (Film, Slides, and Negatives)

NOTE:  If scans of aerial photography will be used for oversized reproduction, follow the scanning recommendations for the next largest format (e.g., if your original is 70 mm wide, follow the speicifications for 127 mm wide roll film to achieve 8,000 pixels across long dimensions).

For Originals With Format Range 70 mm Wide and Medium Format Roll Film; Size range Smaller than 10 Square in.:

File format:

Pixel array:

Resolution:

Bit depth:

or

For Originals With Formats Range 127 mm Wide Roll Film, 4x5 inches and Up To 5x7 Inch Sheet Film;  Size Range Equal To or Larger Than 10 in. and and Up To 35 Square in:

File format:

Pixel array:

Resolution:

Bit depth:

or

 

For Originals With Format Range Larger Than 127 mm Ride Roll Film and Larger Than 5x7 in. Sheet Film; Size Range Equal To Or Larger Than 35 sq. in:

File format:

Pixel array:

Resolution:

Bit depth:

-or-

 

Aerials: Reflective Originals

NOTE:  If scans of aerial photography will be used for oversized reproduction, follow the scanning recommendations for the next largest format (e.g., if your original is 8x10 in., follow the specifications for formats larger than 8x10 in. to achieve 6000 pixels across long dimensions.

For Originals With Format Range Smaller Than 8x10 in; Size Range Smaller Than 80 sq. in:

File format:

Pixel array:

Resolution:

Bit depth:

-or-

 

For Originals With Format Range Equal To or Larger Than 8x10 in. and Up To 11x14 in.; Size Range Equal To or Larger Than 80 sq. in. and up to 154 sq. in.:

File format:

Pixel array:

Resolution:

Bit depth:

-or-

For Originals with Format Range Equal To or Larger that 11x14 in.; Size Range Equal To or Larger Than 154 sq. in

File format:

Pixel array:

Resolution:

Bit depth:

-or-

3.3 Minimum Image Quality Requirements For Digital Access and Thumbnail Image Files

Access Images:

File format:

Pixel array:

Resolution and bit depth:

 

NOTE:  In creating access images, scanned images should have Unsharp Mask applied to them in Photoshop.  The following settings are recommended:

 

Thumbnail Images:

File format:

Pixel array:

Resolution and bit depth:

3.4 Additional resources

 

4.0 Best Practices for Newspaper Digitization

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