Historical Practice



Documents -- Printed matter, manuscripts
Legible, printable reference image



Pictorial items -- Prints and photographs
Reference surrogate













Current Practice -- Documents



For-information-only class
Routine must-be-scanned-bound class
Derived-from-microfilm class
No OCR class

Legible, printable reference image



Examples:

Current Practice -- Documents





Rationale for legible-only practice

Current Practice -- Documents





Typical master/archival image types for legible-only

Lossless compressed bitonal page images
300-400 dpi, CCITT Group IV

Lossy compressed tonal (grayscale) page images
200-300 dpi, JPEG (not fully satisfactory)









Current Practice -- Documents





Art-of-printing class
Rare, large, and/or valuable class
OCR class (no LC examples)

High resolution archival capture

Examples:





Current Practice -- Documents





Rationale for high resolution practice

High artifactual value

Hard to handle

Likely to be selected for "art" reproduction

OCR contemplated









Current Practice -- Documents





Typical archival (master) image types
for high resolution



Uncompressed tonal (grayscale or color) page images
300 (or greater) dpi, uncompressed (or LZW?)

Lossless compressed bitonal page images
600 dpi, CCITT Group IV







Mantra





For viewing and reference-use printing, high quality digital images are better than microfilm images.

For fine reproduction, e.g., printed publications, high quality digital images can permit the production of printing plates as successfully as copy photographs.

Once systems demonstrate capability to migrate data, high quality digital images will be accepted for long-term preservation.









Current Practice -- Pictorial





When the original item is to be scanned

High resolution archival capture

Example:

HABS/HAER architecture negatives

Civil War prints









Current Practice -- Pictorial





When copy intermediate is to be scanned

Moderate resolution capture



Example:

Copy negative file











Current Practice -- Pictorial



Archival (master) image



Higher resolution
5000 pixel (long side) tonal image (grayscale or color), uncompressed

Moderate resolution
3000 pixel (long side) tonal image (grayscale or color), uncompressed



(Yes, these are on the high side.)









Mantra





For fine reproduction, e.g., printed publications, high quality digital images can permit the production of printing plates as successfully as copy photographs.

High quality digital images can fill all the user needs that are presently provided by photographic copy negatives or interpositives.

Once systems demonstrate capability to migrate data, high quality digital images will be accepted for long-term preservation.











Document Resolution Measurement Units





LC tends to describe document or page images in terms of the dimensions of the original

Examples: 150 dpi, 300 dpi, 600 dpi













Document Resolution Measurement Units





LC typical bitonal images:

8.5x11 page/300 dpi 2550x3300

6x9 page/300 dpi 1800x2700





Cornell preservation bitonal images:

8.5x11 page/600 dpi 5100x6600

6x9 page/600 dpi 3600x5400







Pictorial Resolution Measurement Units



LC tends to describe pictorial images in terms of the "dot count" without regard to the dimensions of the original.



Archival files in next contract:

5UA 5000x4000 window

4UA 4000x3000 window

3UA 3000x2000 window







Pictorial Resolution Measurement Units



Reference files in next contract:

CRI 640x480 window



Videodisc-era carryovers

560x420 window



Thumbnails

150x150 window





For Comparison





VGA 640x480

LC W95 desktop 800x600

SVGA 1024x768





















Need for Multiple Versions



Archival ("proto-preservation")

Reference and/or printing

Thumbnail/inline

On-the-fly generation begins to emerge







Multiple Versions -- Documents

Legible-only class

Page-turning device ("binder")

Inline GIF tonal image

400-800 pixels across

Master/archival image

300 dpi bitonal

200-300 dpi tonal compressed





Multiple Versions -- Documents

Broadside worst-case oversize (under discussion, no decision yet)

Bib record thumbnail (first page only)
GIF tonal, 150 pixels across

Searchable text inline
GIF tonal, 250 pixels across

Page-turning device ("binder") inline
GIF tonal, 400-800 pixels across

Reference image (fetchable)
JPEG tonal (some examples 2500 pixels across)

Master/archival image
Uncompressed 300 dpi tonal (some examples 5000 pixels across)





Multiple Versions -- Pictorial



Pictorial (highest quality type)

Bib record thumbnail
GIF tonal, 150 pixels across
filename ends "t"

Reference image (fetchable)
JPEG tonal, 640x480 window
filename ends "r"

Master/archival image
Uncomp (LZW?) 5000 pixels across
filename ends "u"

Compressed display image (under discussion)
JPEG 5000 pixels across
filename ends "v"





Producing Derivatives



Bitonal Document Master Images
Produce inline tonal image (interlaced GIF)



Gray (4 bits deep)
Blur
Rescale
Sharpen



Most promising for on-the-fly derivation







Producing Derivatives



Tonal Document Archival Images
Produce inline tonal image (interlaced GIF)



Drop grayscale to 4 bits deep

Color drop to 8 bits deep (indexed color)

Rescale

Sharpen (?)



Less promising for on -the-fly







Producing Derivatives

Pictorial or high quality document

Master/archival

no non-reversible enhancements, e.g., no sharpening
greater bit depth (?)

Reference image

rescale
sharpen
may contrast stretch
may use non-linear tonal distribution for monitor display

Thumbnails

drop to 8 bits deep
creative use of blur and sharpen









Capture Devices





Flatbed scanners

Practical when handling or conservation permits

May go to 11x17 inches (map scanner to 32x24 inches)

High end devices have greater ability with broader brightness range include control of black and white points







Capture Devices





Overhead devices

Some are camera mounted linear CCD arrays

Some are camera mounted area-capture CCD arrays

Preferred when items cannot lie flat or cannot be inverted

Typically have excellent software













Capture Devices



The greater the power and control, the more skill required.

View camera controls

Software setup

Management of ambient light

More complex workstation



Increased investment for high end devices means
more headaches re: obsolescence.







Bonus Slides
Gleanings from Pictorial RFP



Image Tonal Range -- 1

The tonal range of the delivered digital images delivered shall be representative of the original scene or artifact or, in the case of images whose source is a photographic negative, of the expected representation of the original scene when the negative is reproduced as a positive print.

For prints (black-and-white or color), the objective is to reproduce the items as they exist in the collection.

For negatives and original positive transparencies , the objective is to create a positive image in a manner that may be compared to creating a print (black-and-white or color) in a darkroom.







Bonus Slides
Gleanings from Pictorial RFP



Image Tonal Range -- 2

Providing images with acceptable tonal qualities shall require that the scanning operator exercise judgement when producing the images. The operator's judgement required to achieve the required outcome shall be especially critical when imaging color items. Utilization of general imaging industry standards and those as agreed to and established during the contract startup and testing phase shall be followed. Additionally, consultation with Library staff may, when necessary, be required in order to ensure that appropriate operator judgements are made throughout the run of a particular batch or scan group.







Bonus Slides
Gleanings from Pictorial RFP

Tonal Value

For a black-and-white scene with a typical range of brightness, e.g., a landscape in daylight or a conventional studio portrait, a histogram shall show continuity of sampling and shall include values ranging from black to white. Some pixel values shall fall in the range of 5-12 (black) while some values shall fall in the range 243-250 (white).

For color images with typical scene brightness that include white or black elements, similar values shall be provided for RGB (red, green, blue) renderings of white or black, i.e., a white area shall have values of r=243-250, b=243-250, and g=243-250 and a black area shall have values of r=5-12, b=5-12, and g=5-12.





Bonus Slides
Gleanings from Pictorial RFP

Cropping -- 1

The Library wishes to provide researchers with a reproduction of the entire original item. Thus, images shall be framed and cropped to show the entire original item and beyond the item's edges. For negatives or other transmitted light items, each digital image shall reproduce that item's actual-image area, the border on the film that surrounds the image area, and a portion of the background (light box or scanner top) beyond the edge of the film. A similar approach shall be followed for reflected-light items; the whole print, whole mount, and a portion of the background (beyond the mount) shall be reproduced.

In the delivered images, the amount shown beyond the edge of the item shall be no less than 1.5 percent of the dimension of the long side image. Thus, for a 3,000 x 2,000-pixel image, the border beyond the reproduction of the original item shall consist of approximately 35 pixels on all four sides; for a 640 x 480-pixel image, the border shall consist of approximately 10 pixels on all four sides.







Bonus Slides
Gleanings from Pictorial RFP



Cropping --2
Multiple Items on a Single Mount

When multiple prints are mounted on a single board, e.g., eight Civil War portraits on one cardboard mount or three small prints mounted on a single scrapbook page, each image on a multiple-print mount shall be captured separately. Framing for each print shall extend beyond the image proper. Specific task orders may additionally require the production of an image that captures the full physical item, i.e., a Civil War mount with eight portraits or a full scrapbook page with three prints.