Lesson 4: Input and Output

1. Lesson 4:Input 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 • It’s 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 you’ll 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) • Don’t resize repeatedly • Work at full resolution

9. Don’t 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 can’t generate additional information • Enlargements will not be sharp when viewed up close

11. 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 Printers: Ink Jet • Ink jet printers work by spraying droplets of colored ink - cyan, magenta, yellow, black

12. Advantages Saturated colors True 24-bit color at each pixel Disadvantages Expensive Expensive to use Wasteful of supplies Slow Printers - Dye Sublimation • Work by evaporating dyes from donor sheets onto paper

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