Presented by:MU Libraries Digitization

MOBIUS Annual Conference 2012

Brian CainFelicity DykasRegina GuccioneElaine Huntsucker

160,000 Pixels

D P IDots Per Inch

Pixel

Dot

200 DPI (DOTS PER INCH) 400 DPI (DOTS PER INCH)

200 DPI 400 DPI

1 2 3 4 5 6 7 8 9 10

1

2

3

4

6

7

8

9

10

The number of bits used to indicate the color of a single pixel in a bitmapped image.

• 1 bit = 21 = 2 color channels

• The more bits of information per pixel, the more available colors and more accurate the color representation.

• An image with a bit depth of 1 has pixels with only two possible values: black and white.

8 BIT DEPTH 24 BIT DEPTH

Both of these images are 400dpi

8 Red ComponentsX

8 Green ComponentsX

4 Blue Components=

256 RGB Color Variations

8 bit = 2⁸ = 256

256 Red ComponentsX

256 Green ComponentsX

256 Blue Components=

16,777,216 RGB Color Variations

24 bit = 224 = 16,777,216

Two most common color modes are RGB and CMYK

RGB (Red, Green, Blue color channels) is an additive color process (red+green+blue=white)

CMYK (Cyan, Magenta, Yellow, blacK color channels) is a subtractive color process (cyan+magenta+yellow=black)

Most common color mode for digital images

Produced from the measurement for each pixel of the amount of light passing through RGB filters in imaging hardware

Creates a color image through a mixture of each color channel depending on these measurements (0-255 for each RGB value at 24 bit)

(255-0-0)

R G B

(0-255-0)

(0-0-255)

24 bit image: 256 X 256 X 256 = 16.8 million possible colors

NO Red channel

NO Red and Green

NO Green Regular color

NO Blue and Red

NO Blue

NO Blue and Green

More related to prepress work and printing

Method used in inkjet and laser printers for creating color images

Not a common color mode for digital images, usually a conversion from RGB

Bitonal, binary, black and white, or 1-bit monochrome image

Records 1-bit of information (0, 1) depending on whether the pixel is light or dark

Assigns pixels shades of gray on gradient between white and black

Grayscale 8 or 16 bit determines amount of shades of gray available

What is a file format?File formats include .tiff, .jpeg, .pdf, essentially specific structures for the encoding of data that allows software to interpret and display the image. File formats usually include image data and metadata about the file itself and the image. What is compression?Compression is the process of reducing the amount of data stored for a digital image file, usually utilizing some sort of algorithmic formula. Depending on the method, compression can either be “lossless” or “lossy”, meaning reconstruction of the original digital image data may or may not be possible.

Adoption and accessibility

Metadata creation

Range of functionality and flexibility

Long-term access and support

Preservation and storage considerations

What are some important considerations when choosing a file format?

Software upgrades no longer support file format

File format itself is updated and legacy files become obsolete

Slow adoption and limited software options

Functionality no longer current with contemporary environment

File format is no longer supported or is withdrawn due to market forces

What problems may arise with file formats?

Not any one format, proprietary format for each camera

Holds all the data captured by the camera sensor

Typically only understandable by camera-specific software, some third-party support available

Unsure long-term viability and support for each format

DNG (Digital negative) format by Adobe possible solution for universal RAW data conversion

Royalty free file format with a long history and wide adoption

Can be thought of as a “file wrapper” that is able to preserve all image data and tags found in raster and vector images

Very flexible format that accommodates full RGB colors, high bit-depth, all associated metadata, and any image resolution

Capable of storing lossless images

Tagged Image File Format (TIFF)

Can result in very large file sizes

Rights held by Adobe

JPEG was designed to limit file size for storage and for quick display

Uses “lossy” compression algorithms to reduce amount of image data

More limited color data (not full RGB) and reduced spatial resolution

Wide adoption and well supported

Smaller file size, however this is due to permanently discarded image data

Joint Photographic Experts Group

Update of JPEG format, described as “lossless” (debatable)

Uses Wavelet compression techniques superior to regular JPEGs, however color data is still lost and spatial resolution data is modified in the compression process

Master

Display

Thumbnail Because of the nature of the

format, it can store and deliver varying versions of the image from one file

Needs specialized software to view and use JPEG2000, relatively low adoption and use rate

Originally a proprietary format of Adobe, but was released as an open standard in 2008

Meant as a “wrapper” with structured page description for complex documents created using multiple component types (text, images, etc.). Not consistent encoding across all iterations of PDF software

Widely adopted and used, however varying forms of image compression and manipulation occur when saving as a PDF

PDF/a is an offshoot of PDF v1.4, meant for long-term preservation and is more restrictive in the content and types of structured data saved in the file

Portable Document Format

GIF: only supports 8 bit (256 colors), lossy compression produces small file sizes, wide adoption on web

PNG: GIF replacement, supports true color (24 bit +), no CMYK support, lossless compression, not as commonly used as GIFs but growing

BMP: very simple format, records location of pixel and its color (up to 24-bit), does not store metadata

PSD: proprietary Adobe Photoshop File, dependant on Adobe software and support

Comparison between TIFF, PNG, GIF and JPEG file size for 400 ppi color image

TIFF

JPEG/GIF

PNG

ColorComparison between color, grayscale and bitonal TIFF files at 400 ppi resolution

Grayscale

Bitonal

400 ppi

200 ppi100 ppi

Comparison between 24 bit color TIFF files at 400, 200 and 100 ppi resolutions

It depends …Try for good versus bestEstablish acceptable minimum level

of work, and make it the benchmark. (Meissner, 2011, slide 9)

Priority is to create and preserve a high-quality master copy of a digital image

Priority is to provide access to users

Create a fully documented high-quality ‘digital-master’ from which all other versions … can be derived.

Digital master highest resolution and bit depth that is

both affordable and practical preserves to the greatest extent

possible the authenticity and integrity of the original information.

(Hughes, 2004, p. 166-167)

• More Product, Less Process• Maximize user access (preeminent goal)• Golden minimum “good enough”

digitization is realistic• Arrange, describe and digitize at a

common aggregate level• Reserve exception digitization effort only

when warranted• Accomplish more digitization by trying to

do less• (Elings)

Then … Now …

Craft Assembly Line

Rigorous quality control Quality control not as rigorous

Few highly skilled students working

More students working more hours

Digital image editing Consistency in product produced, not perfection

Completing 17-39 books [per month]

Completing 500-800 books [per month]

(Henry, 2008)

Goals and prioritiesAudienceMaterial Institutional resources

o Goals and priorities of the institution and the projecto Grant requirements o Requirements of partnerso Long-term planso Fit the file to the purpose (Kenney, 2000,

p. 105)o Archival/preservation copy versus

access copy

o Target user needso Will users want to zoom in and view

detail?o Will users need OCR to search the

content?o Will users want to print the digital image?o Will users be interested in the artifact as

well as the content? o What image performance is required?

o Text versus graphics/pictureso Text with a crisp font versus

handwritten texto Black and white versus coloro Condition of itemso Need to retain the digitized items

o People and skillso Equipment / technologyo Digitization equipment

o Infrastructure / platforms for access and storage

o Time and production targetso Constraints imposed by source material

(condition and types)

• Factors that will influence decisions [throughout the digital life cycle]– The reasons for digitization– The materials to be digitized, especially their

condition and informational content– The level of fidelity to the original that is required– The technical and financial resources that are

available to the project, and the scale of the project

– The potential uses and users of the digital objects– Any specific desired outcomes for the physical

objects that are to be digitized.(Hughes, 2004, p. 165)

At times, your choice comes down to time and money: convert fewer items at a high level or more items at reduced quality. (Kenney, p. 25)

Strive for good quality that meets user needs

Whatever you decide, be consistent Document your standards / criteria

A frequent concern is how to achieve the proper balance between quality and rate of production. Having a clear vision of the use of the digital materials and the quality required will help to focus such decisions. (Hughes, 2004, p. 165-166)

Compromises in quality are acceptable when the purpose of imaging is a matter of access only and preservation of information of the original has been assured through conservation or preservation reformatting. However, when the intent of digitization is the reproduction or replacement of the original, the highest possible resolution and tonality must be applied. (Ballinger, p. 160)

Tiff, uncompressed and unedited The standby (Nadal, 2012b) Various dpi: 300-600; choose the highest

possible for type of material 24-bit color

PDF/A Very preservable (Nadal, 2012b)

Digital negative May be valuable as a digital preservation

format for the specific use-case of born-digital photography (Nadal, 2012b)

• Long-term access will likely include the need to o Refresh – moving files from one physical storage

medium to another to avoid obsolescence or degradation of the storage medium

o Migration – moving files from one encoded format to another

o Emulation – develop new tools that will re-create the conditions under which the original data were created; similar to migration, but focuses on the application software

o (Hughes, 2004, p. 205)

Questions?