Introduction to Scanning

Why Digitize? Provide better access Protect fragile or valuable materials in your collections Digital surrogates will help preserve unique objects by protecting them from handling.

Why Digitize? Ability to search, discover, and manipulate images, text, and sound in new contexts will increase and extend use of collections. Wider dissemination of unique collections will encourage scholarly use. Digitization will allow integration of related materials on multiple hosts in "virtual collections.“ Digital content can lead to new knowledge by enabling scholarly use that was not possible with print collections, (i.e. digital analysis and scholarly communication.)

General Questions to Ask (we will come back to this later) Do we have? The money The skills The capacity The technical infrastructure Carry out? Benchmarking study Copyright study Feasibility study Technical pilot study

Still Image Scanning Reflective – Prints or photographs (8x10 etc.) Transparent (film) – Negatives

Digital Object Data (the content or "essence" of a digital file) and the metadata describing it, regarded together as a single entity. Also known as a digital asset, an information object, or an information package. May also refer to “born digital” objects.

Digital Object Is made up of 2 components: The digital asset: – image, sound, book, audio, data set, etc. It’s affiliated metadata (“data about data” – Descriptive: facilitating resource discovery and identification – Administrative: supporting resource management within a collection – Structural: binding together the components of complex information objects

Analog to Digital Conversion Specifications for digitization Specifications for information creation

Pixel (Building Block of an Image) Image is converted to a series of pixels laid out in a grid Each pixel has a specific color, represented by 1s and 0s Pixel-based images are called “raster” images or “bitmaps”

Bit Map Image A raster or bit-mapped image is a digital picture made up of rows of pixels in a grid. The properties: Resolution Dynamic range/Bit Depth Pixel size and shape First Digital Image (176 x 176 pixels) Russell Kirsch, NIST, 1957

Resolution Understood as “dpi” or “ppi” – Dots Per Inch or Pixels Per Inch Examples: 8x10 print scanned at 300ppi = 2400 x 3000 pixels 35mm slide (24x36mm!) scanned at 300ppi ≈ 212 x 318 pixels

(Scalable) Vector Graphics AsteroidsBattlezoneStar Trek Early and popular examples of vector graphics

(Scalable)Vector vs. Pixel-Based (Scalable)Vector graphics, not made up of a grid of pixels, Vector Graphics are comprised of start and end points that lead through locations called control points. Font/letters are usually in TrueType, which is vector.

Image Resolution (cont.) Often referred to as “dpi” or “ppi” RATIO of number of pixels captured per inch of original photo size – 8x10 print scanned at 300ppi = 2400 x 3000 pixels – 35mm slide (24x36mm!) scanned at 300ppi ≈ 212 x 318 pixels 8x10 photo 35mm slide

October 21, 2004L597: Humanities Computing Image Resolution “Spatial resolution” refers to pixel dimensions of image, e.g., 3000 x 2400 pixels Flatbed scanners have fixed focus, so they know how big the original is; digital cameras don’t Caution: DPI (per inch) is a relative measurement of resolution, and is highly dependent on the size it’s scaled.

Scanner vs. Camera A digital camera can capture data based on the mega-pixel ability of its CCD. For example, an 8 mega-pixel digital camera shoots at approximately 3264 x 2448 pixels – There is not resolution setting per se Scanner is set by the technician and image it is scanning. It can be set at 72 dpi, 100 dpi, 300 dpi and higher

Bit Depth Bit Depth is determined by the number of bits used to define each pixel. 1-bit bitonal 8-bit grayscale 24-bit color

How Color is Handled RGB – Scanners generally have sensors for Red, Green, and Blue – Each of these “channels” is stored separately in the digital file – 8 bits for each of 3 channels = 24 bit color CMYK (Cyan, Magenta, Yellow and Black) is used for high-end “pre-press” printing purposes

Spatial Resolution DYNAMIC RANGE is the range of tonal difference between the lightest light and darkest dark of an image.

Pattern versus Symbol in Code Coded pattern: 3 mm letter “e” at 600 dpi scanned from negative microfilm Coded symbol: e = (ASCII code 101) -When we talk more when we learn about OCR 4,900 bits vs. 8 bits Pattern or “Bit map” ASCII

Bit Depth Refers to number of bits (binary digits, places for zeroes and ones) devoted to storing color information about each pixel 1 bit (1) = 2 1 = 2 shades (“bitonal”) 2 bit (01) = 2 2 = 4 shades 4 bit (0010) = 2 4 = 16 shades 8 bit ( ) = 2 8 = 256 shades (“grayscale”)

Compression Makes images files smaller Images must be “decompressed” Lossy Lossless

File Formats TIF JPEG 2000 JPG (is the most used image file format.) GIF PNG RAW

Specifications Considerations Create master image when scanning – Capture all “important” information – Meets all foreseeable needs – For long-term storage and later use Create derivatives for specific uses later – Web delivery – Printing – Publication

Types of Files Produced Master or Archival – The source files for all other digital files and ensure the long-term usability of the digital information. Access Thumbnail

Master Files TIFF (uncompressed) – Virtually unanimously recommended by digital imaging best practices – “De facto” standard – Proven track record – Lossless RAW is camera only, not for scanners – Not entirely open, each camera maker has their flavor – Need special software to view it – Large file sizes JPEG2000 (compressed) – Not patent-free – Up-and-coming but not quite there yet – Supports embedded metadata – Uses wavelet-based compression – Visually lossless

Access/Delivery Files Consist of low-resolution files Some systems creates these for you “on the fly” Some require you create “by hand” or with desktop tool Speed up delivery of images All formats have an access version or derivative separate from the master file

Practical Considerations Higher is not always better Scan at highest resolution necessary to achieve your stated purpose, no higher Capture once, use many times – Create “master” image when scanning – Create “derivatives” for specific uses later

Practical Considerations Always scan at no more than your maximum optical resolution of the scanner. Can cause interpolation, which is basically the scanner adding extra pixels merely by average each of its neighbor pixels—I kind of compression on the fly.

Practical Considerations How much storage can you afford Does you audience need ultra-high resolution Files sizes can impeded systems Be realistic about your needs versus your resources Will you scan in-house or use a vendor Costs will be discussed later in class

Scanning Specifications See hand out! 8x 10 and larger 6,000 pixels on longest side 6,000 pixels on the long axis of the image (600 pixels per inch (ppi) for an image 10 inches long) COLOR:24 bit RGB setting, (8 bits per channel) B&W 8 bit Grayscale or 24 bit setting color,(we will do 8 bit Grayscale)

Class exercise In-class Exercise: Each group will scan at least 3 to 4 archival photographs using the flatbed scanner. You must rotate and crop using Photoshop, follow this tutorialtutorial Save file as.tif for "master“ version, and name it with group and your full name, like "group6_mark_wolfe.tif" For the " access“ version save as, select.jpg, append "web" at the end of file name.jpg, like "group6_mark_wolfe_web.jpg" For "access" version, in Photoshop, go to Image, Image Size, select Resolution = "100" for dots per inch. Save file.