How to digitise
old photos.

The Library of Congress’s advice for personal collections: scan documents and 6 × 4 or 7 × 5 inch prints at 300 dpi, and use 400 or 600 dpi for any print you might enlarge to 10 × 8 inches or more. An earlier version of the handout adds that anything above 600 dpi may be unnecessary for prints, since more dots also mean bigger files.

Dpi (dots per inch, often used interchangeably with ppi) counts the pixels captured for each inch of the original. At 300 dpi a 6 × 4 inch print becomes 1,800 × 1,200 pixels, enough to reprint it at the same size. At 600 dpi it becomes 3,600 × 2,400 pixels, enough for a 12 × 8 inch print at 300 pixels per inch.

Archives aim a little higher. The Federal Agencies Digital Guidelines Initiative (FADGI), written by US federal agencies including the Library of Congress and the National Archives, asks for 400 ppi for photographic prints at its three-star level, “a very good professional image”, and 600 ppi at its top level. If you are unsure, scan at 600 dpi: it sits at the top of both ranges, and you only have to handle a fragile print once.

Both, for different jobs. The Library of Congress’s digital preservation blog calls TIFF “the preferred format for digital photo preservation” because it keeps the most of what the scanner captured, and LZW compression can shrink a TIFF without losing any data. JPEG’s compression is “lossy”: it makes small files by discarding some of the data.

The Library of Congress names greyscale, a palette of up to 256 grey tones, as best for black-and-white photographs. With the usual settings of 8-bit greyscale and 24-bit colour, a greyscale scan is a third of the size.

When in doubt, scan in colour; a greyscale copy takes seconds to make later. FADGI images every photograph in colour at its three-star level and above, black-and-white originals included.

If there is writing on the back of a print, scan that side too and add “-back” to the file name. Our guide to labelling old photos covers what to write, and how.

Start every file name with the date. The Library of Congress recommends a yyyymmdd structure at the beginning of the name, such as 20100915-wedding.jpg, folders within folders, and a naming system you keep consistent. With the date first, files sort themselves into order.

• Folders by person, place or event, such as Family Photos / 1987 Spain.
• File names by date, subject and number, such as 19870614-beach-001.tif.
• Unknown dates: fill the parts you don’t know with zeros, such as 19620000-wedding-001.tif, so the file still sorts by year.

The Library also suggests keeping a printed summary of what is where alongside your storage. Who is in a photo, and why it matters, belongs in a caption rather than a file name; our guide to what to do with old family photos covers that part.

The Library of Congress suggests one copy on your computer and others on separate media, such as portable drives or online storage, kept in different places. Our guide to backing up family photos explains the 3-2-1 rule. And keep the prints: the US National Park Service’s guidance on colour photographs is to use digital copies for access, not preservation.

Scanning gives you files. Ancestorii is where your family looks at them and adds what they know. On the website, upload JPEG copies to your family Library, up to 20 at a time, into folders you can give a name, a description and a date. iPhone HEIC photos are converted to JPEG automatically.

Then put the best into albums, where each photo can carry a name, a date as loose as “Summer 1994”, a thread called The Story that relatives add to, and voice notes. Only the people you invite can see them.

The Free plan gives the whole family 1 GB, with files up to 20 MB. Premium, at £3.99 a month per family, gives 100 GB and files up to 10 GB. A 600 dpi colour TIFF of a 6 × 4 inch print is about 26 MB before compression, so upload JPEGs and keep the TIFF masters in your own backups. Ancestorii is for sharing and explaining photos, not a replacement for those copies.