Lesson 4: Input and Output

1
Lesson 4Input and Output

• Digital Photography
• MITSAA
• IAP 2002
• Rob Zehner

2
Outline

• Scanners
• Different types
• Compare contrast
• Printing digital images
• Different types of printers
• Compare contrast
• Preparing images for print

3
Why Scan?

• Film is a great image capture medium
• Cheap
• Ultra-high resolution
• Its been around for years
• Digital offers new opportunities
• Digital printing no darkroom!
• Image manipulation, touch-up is easy
• Use film photos on Web sites, share with friends

4
Flatbed scanners

• Least expensive kind of scanner (100-1000)
• Optimized for reflective materials (paper,
  prints)
• Typically has a small contrast range
• Can be adapted to scan film with auxiliary light
  source
• Not optimized for handling transparencies

5
Film scanners

• More expensive than flatbeds (500 - 5,000)
• Typically have very high contrast range
• Even good film scanners will not be able to
  capture the full tonal range of a black white
  negative
• Capable of scanning at 3,000 - 4,000 dpi
• Usually come with software to make the process
  easier - scratch dust removal, etc.

6
Drum scanners

• Most expensive
• Originals are taped to a cylinder, which is spun
  rapidly and scanned with a single PMT
• Advantages
• Very good sharpness
• Extremely large contrast range
• Disadvantages
• Negatives must be de-mounted, taped, often coated
  with index-matching oil

7
Scanner fallacies

• All resolution figures are not equal
• Sharpness is what is really important
• Beyond physical resolution limit, more pixels
  carry no additional information
• Flatbed transparency adaptor is not the same as
  a film scanner
• Dmax of scanner will determine the results for
  transparent media

8
Before printing / after scanning

• Scan to give you the number of pixels youll need
• Printer resolution x output dimension
• Rule of thumb 300 ppi is adequate
• Keep your data stream short
• Avoid lossy compression (use TIFF, not JPEG)
• Dont resize repeatedly
• Work at full resolution

9
Dont rely on unknown factors

• Give image to the printer at exact printer
  resolution
• Otherwise, the printer will re-scale it using
  some unknown algorithm
• Use color calibration
• Calibrated input sources
• Calibrated displays (Adobe Gamma)
• Calibrated printers

10
Image resizing

• Film grain determines enlargement limit
• Digital pixellation determines enlargement limit
• This can be overcome by rescaling the image
• Software will use an algorithm to generate
  intermediate pixels
• Whatever you do, you cant generate additional
  information
• Enlargements will not be sharp when viewed up
  close

11
Printers Ink Jet

• Ink jet printers work by spraying droplets of
  colored ink - cyan, magenta, yellow, black

• Advantages
• Cheap to buy
• Fairly high resolution
• Nice colors
• Can handle large paper

• Disadvantages
• Slow in color mode
• Supplies are expensive
• Photo paper 1/page
• Ink cartridges 30
• Archival life ??
• Epson makes pigment inks they claim will last 100
  years

12
Printers - Dye Sublimation

• Work by evaporating dyes from donor sheets onto
  paper

• Advantages
• Saturated colors
• True 24-bit color at each pixel

• Disadvantages
• Expensive
• Expensive to use
• Wasteful of supplies
• Slow

13
Printers - Photo Printers

• Work by variety of processes involving
  photosensitizing transferring dyes (e.g. Fujix)

• Advantages
• Very low cost per print
• Very good colors
• Lightfastness should be similar to traditional
  photographs

• Disadvantages
• Too expensive to own at home
• Commercial printers can charge large mark-up