Scanning old photographs, negatives and slides

Before scanning: handling

• Handle photographs with clean hands or clean nitrile gloves, and by the edges; do not touch the image area.
• Remove dust with a hand-held air blower. The Library of Congress points out that even a soft brush can scratch a photograph, and does not recommend canned compressed air.
• Do not wash photographs or clean them with solvents. Have torn, mouldy or stuck-together photographs assessed by a conservator.
• Only take photographs out of an album if they come away without force. It is often safer to scan the whole album page.
• Clean the scanner glass before every batch.

What resolution to choose

Scan resolution (in ppi) sets how many pixels fall on each inch of the original. The calculation is simple:

required scan ppi = target print ppi × enlargement

The enlargement is the ratio of the print’s long side to the original’s long side.

Paper prints

Original	Target	Enlargement	Scan for 300 ppi output
9 × 13 cm	9 × 13 cm (1 : 1)	1×	300 ppi
9 × 13 cm	18 × 26 cm	2×	600 ppi
9 × 13 cm	27 × 39 cm	3×	900 ppi
6 × 9 cm	30 × 45 cm	5×	1500 ppi

A paper print carries only a limited amount of detail. Ordinary prints are therefore usually scanned at 600 ppi, and small prints you want to enlarge at 1200 ppi. A higher resolution often captures nothing more than the paper texture or a printing screen, and needlessly inflates the file.

Negatives and slides

Film carries far more detail per unit area, so it is scanned at a higher resolution. A 35 mm frame measures 36 × 24 mm.

• 36 mm ÷ 25.4 = 1.417 inches,
• at 4000 ppi: 1.417 × 4000 = 5669 px on the long side, 3780 px on the short side (21.4 MP),
• printed at 300 ppi: 5669 ÷ 300 = 18.9 inches = 48.0 cm.

Film	Scan resolution	Result	Prints at 300 ppi up to
35 mm, 36 × 24 mm	2400 ppi	3402 × 2268 px	28.8 × 19.2 cm
35 mm, 36 × 24 mm	4000 ppi	5669 × 3780 px	48.0 × 32.0 cm
medium format 56 × 56 mm (6 × 6)	2400 ppi	5291 × 5291 px	44.8 × 44.8 cm

Suitable tools for scanning film are a film scanner, a flatbed scanner with a transparency unit, or “scanning” with a camera: a camera with a macro lens, an even light source beneath the film and a holder that keeps the film flat.

File format

• Archive copy (master): TIFF, 16 bits per channel, unedited, with the colour profile embedded.
• Working copy: make adjustments and retouching in a copy, not in the master.
• For sharing: JPEG in sRGB.
• Name files systematically (year, event, sequence) and back them up in more than one place.

Dust and scratches

Dust on a scan comes from two places: the original and the scanner glass. Remove it physically first, then digitally.

• Infrared dust removal (such as the ICE feature) detects dust and scratches on colour film using an infrared channel. It does not work reliably on classic black-and-white film with a silver image, because silver blocks infrared light much as dust does.
• Retouch in your editor (clone stamp, healing brush) at 100% magnification, a little at a time.
• Automatic “dust and scratches” filters soften the whole image; use them only locally, through a mask.

Restoring faded colour

Colour photographs from the 1960s to the 1990s often fade unevenly: some dyes weaken faster than others and the photograph takes on a strong colour cast, often towards red or magenta.

1. Start with levels or curves on the individual channels: set the black and white points separately for R, G and B.
2. Neutralise the cast using something that was originally grey or white (a shirt, a wall, a road).
3. Add saturation carefully; faded colours are easy to overdo.
4. With automatic colourisation of black-and-white photographs, remember that the colours are a guess, not a restoration. Keep the original black-and-white version as well.
5. Write down what you changed. In ten years’ time you will be glad you did.

Printing the restored photograph

• Size: you don’t have to enlarge a restored photograph. An old 9 × 13 cm print in the mount of a 30 × 40 cm frame looks finer than a blurry enlargement.
• Paper: baryta or smooth cotton paper suits black-and-white portraits; matt or satin cotton paper suits colour family photographs. Compare them in Paper Lab.
• Test print: first print a section with a face and compare it with the original in daylight.
• The original: store it in a PAT-tested enclosure and hang a copy on the wall. See Storing photographs.