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Topics include: Scanner v. Digital Camera-Pros & Cons Basic digitization terms Some common file formats Types of scanners available Things to consider when choosing a scanner A brief scanning how to
The advantages and disadvantages of digital cameras and desktop scanners will be compared on the following slides.
Advantages
Portable for field use
Useful for large format items (ex. maps, posters, & 3D items)
Disadvantages May require
additional equipment (ex. tripod, lights, light stands)
Variations in quality of material (ex. quality of lighting, focus)
Advantages
Ease of use Clarity of images DPI is able to be
controlled Consistent quality Useful for photos,
printed material, & paper documents
Disadvantages
Not portable without a laptop
Not useful for 3D objects
Scanners commonly use light sensors arranged
in a grid-like array to convert light into 1s and 0s that computers can read and translate into
digital copies of the item being scanned
• Bit-The smallest unit of data that can be stored in a computer
Scanners use multiple bits to represent information about pixels of an image
• Pixel-Short for “Picture Element”; Refers to a single dot in a digital image
Individual color pixels of digital images have 3 numerical components which represent a value for Red, Green Blue (RGB).
• Bit Depth-Number of bits used to define each pixel; also called dynamic range
Each single bit is made up of 2 tones• 1 bit (21) = 2 tones• 2 bits (22) = 4 tones• 3 bits (23) = 8 tones• 4 bits (24) = 16 tones• 8 bits (28) = 256 tones• 16 bits (216) = 65,536 tones• 24 bits (224) = 16.7 million tones
Compression-Reducing file size for easier storage, faster processing or faster transmissionLossless compression-shrink file size without discarding any information
Lossy compression-small bits of information are discarded; may or may not impact visual perception
Scaling-changing proportions of an image by increasing or decreasing size; important when printing images
File formats-made up of bits that comprise an image, and header info that describes how to interpret the file
JPEG (Joint Photographic Experts Group)
Compression standard primarily used for still images on the WWW. JPEG is traditionally lossy compression; not particularly good for archiving images
JPEG 2000
new image compression standard that allows for greater compression while maintaining high image quality; also has a lossless option
Not widely supported by scanners or software
TIFF (Tag Image File Format)
very good for archiving images; a widely supported format; supports lossless compression; larger file size than JPEG
PNG (Portable Network Graphics)
not as popular as TIFF or JPEG, supports high quality lossless compression, particularly for 24 bit photographs; PNG lossless files generally smaller than TIFF
Flatbed ScannerMost common type of scanner; Easiest to use; vary widely in terms of cost; entry level units can be less than $100; many have attachments for scanning slides
Sensors and light source mounted on moving arm sweep past media
What types of materials are going to be digitized?May dictate what type of scanner you buy—flatbed, sheetfeed, film scanner etc. A flatbed will most likely be used for image scanning
CostFlatbed scanner prices range from under $100 to thousands
ResolutionScanner Resolution typically measured by 2 numbersex. 1200 x 2400
Smaller number is most important; refers to optical rating of scanner; a 1200 dpi scanner takes 1200 color samples per inch
Resolutions greater than optical rating are interpolated (some scanners list ratings as high as 9600 dpi)
Interpolated scanning estimates pixels of average color between real pixels
Pictures may come out blurry
Size of scanning surfaceLargest flatbed scanners typically 12 x 17
Anything larger will have to be done with large format setup or shot with a digital camera
Many flatbed scanners are designed for ease of use
Higher end models generally have more features and more advanced image software which can make use more complex
Most flatbed scanners and software vary, but basic use is similar
Step 1: Install software that was bundled with scanner
Step 2: Lay item face down on scanning surfacePosition as straight as possible, for best results
Step 3: Open scanning software on your computer
Mode will depend on source material
If scanning TIFF for master files set dpi to max level
If scanning JPEG 300 dpi is minimum acceptable level, 600 will likely soon be the standard
Click Save Icon (Shown on previous slide) Give Picture a File name Choose File Type (TIFF, JPEG, Etc.) Choose Where on your computer you want the image saved Click Save
Some scanner software allows for more image manipulation than others
Software packages like Adobe Photoshop or Gnu Image Manipulation Program (freely available) and many others can be used to manipulate/enhance images after scanning
TIFF excellent for archiving or making high quality prints; can derive JPEG or other file types from TIFF images
Very large file sizes—much storage space needed
If you plan to edit photos beyond basic cropping etc. TIFF format is preferable
JPEG are compressed image filed Developed for use on Web Much smaller than TIFF Great if your are most interested in
displaying pictures online, or making smaller sized prints
Not good as master files if you plan to manipulate images
Quality degrades when file is saved and re-saved
JPEG is best format for images in a CONTENTdm image collection
Small size makes JPEG files ideal for FTP transmission to server
You may however want to keep a TIFF back up of certain images on disks or a hard drive at your own institution, if space permits
If you are not planning to edit picture, JPEG backups are better than nothing
Reviews of Scanners can be found at several websites:
CNET-www.cnet.com Epinions-www.epinions.com, search
scanners Type “scanner reviews” into GOOGLE, or
any search engine www.scantips.com – Gives good basic and
advanced information about scanning