Lesson 4: Input and Output Digital Photography MITSAA IAP 2002 Rob Zehner

Outline Scanners –Different types –Compare & contrast Printing digital images –Different types of printers –Compare & contrast Preparing images for print

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

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

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 dpi Usually come with software to make the process easier - scratch & dust removal, etc.

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

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

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

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

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

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

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

Printers - Photo Printers 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 Work by variety of processes involving photosensitizing & transferring dyes (e.g. Fujix)