1. Scanning for Preservation and Access
Jan. 2004
Scanning for Preservation and Access
An Infopeople Workshop
presented by
Matthew Mattson

2. TWO TYPES OF DIGITAL IMAGES
Bitmapped (jpg, tiff, bmp, gif)
Images are made up of individual dots (pixels)
Only suitable format for picture images
Not scaleable
Large file size
Vector based (Illustrator)
Images are mathematical formulas (vectors)
Scaleable
Small images, if the design can be vectored

3. Microscopic View Of Digital Images
bitmapped
vector

4. The Three Things You Must Know About An Image (The Holy Trinity)
RESOLUTION
SIZE (PRINT OR PIXEL)
FORMAT

5. DPI DPI = Dots Per Inch More dots per inch, more information captured
Higher DPI means higher quality, ALL OTHER THINGS BEING EQUAL!

6. DO EXERCISE 1 - RESOLUTION
Screens display at DPI
High quality printing starts at 300 DPI
Double the resolution, quadruple the file size
Most software (i.e. browsers) does not understand resolution
Resolution is just the start, by itself it does not tell you enough about the image to know its quality
DO EXERCISE 1 - RESOLUTION

7. Image Size – Pixel and Print
How big is the image (4x6, 8x10, etc.) at its current resolution (print)
Print size only applies to software that can understand resolution
How many pixels are in the image, usually just stated on the long axis
Print size can be determined if you know the number of pixels and the resolution (300 dpi and 1800 pixels means a 6 inch print), and pixels from resolution and print size

8. Changing Print Size DO EXERCISE 2 - SIZE
If you increase the print size, you are decreasing the resolution
If you decrease the print size, you increase the resolution
Pixel size stays the same
DO EXERCISE 2 - SIZE

9. File Format, Compression and Color
Format tells you what software can read the image, if the image has been compressed, and what color palate is available to it
Uncompressed formats (tiff, psd, etc.) are the only acceptable ones for archive images
Compressed formats (jpg) are fine for display images
Restricted color palette formats (gif) are only acceptable for thumbnail images
You will (should) be using tiffs for archive images, jpgs for display (and maybe print) images, and either jpgs or gifs for thumbnail images

10. Bit Depth and Dynamic Range
Bit Depth determines the amount of color (or grayscale) in the image
24-bit color (16,000,000+) is the most humans can see (8-bits each RGB)
32-bit color is “true” color
8-bit grayscale = 256 shades of gray
12-bit grayscale = 1024 shades of gray
No monitor can output 12-bit grayscale
Dynamic Range
Range of tones between dark to light
Higher dynamic range number = more detail

11. How Scanners Work
All scanners, digital cameras, and photocopiers (a binary scanner) work by use of a CCD (charge-coupled device)
Cameras open a shutter to let light hit the CCD, scanners bounce light off of an object to the CCD (transparency scanners pass light through)
Anyone want an explanation of a CCD?

12. How CCDs Work
A type of semiconductor that's sensitive to light, a CCD consists of a 2-D array of individual elements, each of which is, in essence, a capacitor - a device that stores an electrical charge. (Thus explaining the D and one of the C's in the acronym.) A CCD's charge is created when photons strike the semiconducting material and dislodge electrons. As more photons fall on the device, more electrons are liberated, thus creating a charge that's proportional to the light's intensity. With a 2-D array, you can capture an image. Each CCD represents a single-image pixel.
The challenge lies in reading these charges out of the array so they can be digitized. To do this, each individual CCD detector, or pixel, consists of three transparent polysilicon gates over a buried channel of doped photosensitive silicon that generates the charge. The channel is flanked by a pair of channel stop regions that confine the charge.
To read and digitize a particular CCD's charge, the voltages of the three gates are cycled in a sequence that causes the charge to migrate down the channel to the next gate, then to the next pixel, and ultimately down the row until it reaches the end column, where it's read out into a serial register and ultimately sent to an analog-to-digital converter. The sequence of moving the charge from one gate to the next is called coupling (the other C in CCD.
The CCD imaging array is only sensitive to light intensity, not color. One way to capture a color image is to use three CCD arrays, each covered by a filter (usually produced by painting the CCD's surface with dye) that passes one of the three primary colors - red, green or blue. Onboard electronics merge these primary components into a color pixel.

13. Types of Scanners Binary (true black and white)
Photocopiers
Grayscale (can also do Binary)
Early scanners, not seen much anymore except for high speed document scanners
RGB (can also do Binary and Grayscale)
Drum scanners
Large format scanners
Film scanners
Tabletop scanners
Letter size
Legal size
Tablet size

14. Media Types Reflective Transparencies Photos, documents, etc.
Negatives, slides, transparencies
Can be scanned on a tabletop scanner IF you have a true transparency adaptor and IF the media is large enough
If you have a many slides, 35mm negatives or 120 film negatives, consider getting a film scanner

15. Scanner Specs Optical resolution = what the scanner can see
Interpolation resolution = a worthless, higher number that you should ignore
Dynamic range = higher is better
Largest size the bed can scan
Smallest size the optical resolution will support
Transparency adaptor

16. Acquiring Your First Image
Calibration
“Corrects” the scanners color shift
Is run once when the scanner is installed, or anytime it changes computers
TWAIN
Standard for talking to scanners
All you need to acquire an image
Silverfast and other software
Adds more features to the acquisition process
“Sweet Spot” – does your scanner have one?
DO EXERSICE 3 – FIRST SCAN

17. Acquiring an Archival Image
Orientation
Setting the Source
Setting the Image Type
Grayscale, Color, Bit-Depth
Defining the Area
Setting the Resolution
How much is enough
The 6000 pixel standard
Giving yourself room to work
Scale? Adjust?
DO EXERCISE 4 – ARCHIVE SCAN 1

18. DO EXERCISE 5 – ARCHIVE SCAN 2
Using Photoshop
Color Setting
Profiles
Windows Settings
Cropping
Rotation
Borders, text, frames
Image Size Normalization
Resizing
6000 pixels on the long axis
Saving
Tiffs
Naming conventions
DO EXERCISE 5 – ARCHIVE SCAN 2

19. Making Your First Derivative
Print Jpgs
Do you need them?
Resizing
Image Quality Manipulation
Levels – grayscale
Levels – RGB
Moving the midpoint
Saving as Jpgs
Compression (Quality)
Format options
DO EXERCISE 6 – PRINT JPGS

20. DO EXERCISE 7 – DERIVATIVES
Types of Derivatives
Display Images
Resize pixels, resolution or both?
Standard size for display
Saving options
Thumbnails
Resize
Jpg or Gif?
DO EXERCISE 7 – DERIVATIVES

21. DO EXERCISE 8 – BATCH MODE
Batch Processing
Photoshop Actions
A huge time saver
Can’t use on Archive or Print Jpgs
Use to make display images and thumbnails
Record steps that Photoshop will repeat
DO EXERCISE 8 – BATCH MODE

22. Archiving Electronic Files
CDs and DVDs
Which one is right for you
Formats
Creation
Archive Masters and Working Files
Stored where?
Onsite
Offsite
Accessibility
Media Rotation
How often?
When to switch media

23. Producing Prints Laser Prints “Photo” Printers Dye Sublimation
Outsourcing
Digital Images for Patrons

24. Best Practice Guidelines
Resources
Best Practice Guidelines
California Digital Library. Digital Image Format Standards (2001) (
California Digital Library. Best Practices for Image Capture (2001) (
California State Library. Scanning Standards (1999) (
LSTA Digital Projects Manual

25. Evaluation Form