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DRAWINGS, DPI AND FILES

Scan it once.
Scan it right.

A good scan of a drawing needs the right setting, not the highest one.

Too low and the pencil lines blur. Too high and the files balloon without adding anything you can see. Here is what library and archive guidance says about resolution, formats and keeping copies safe.

Plain English, with the sources linked.

Questions this page answers

Two hands lifting a sheet with a crayon sun and swirls onto the glass of an open flatbed scanner on a wooden desk
AI-generated image, not a photograph of a real person or place.

300 DPI for most pages

  • Set the dpi
  • Save a master
  • Keep two copies
  • Scan once, keep for good

THE SHORT ANSWER

300 dpi, saved twice.

For most drawings, that is the Library of Congress
starting point. Go higher only with a reason.

RESOLUTION

Pick the right dpi

300 dpi suits most pages. Use 400 to 600 only if you plan to print the picture bigger.

Try the dpi picker

FILE FORMAT

Save a master file

Archives prefer uncompressed or lossless files such as TIFF or PNG. Make a JPEG copy for sharing.

Which formats?

BACKUPS

Keep two copies

At least two copies in different places, moved to new storage every five to seven years.

Before you scan

A QUICK DPI PICKER

What are you
scanning for?

Pick the job and see the setting the Library of Congress personal archiving tips suggest. Dpi (dots per inch) and ppi (pixels per inch) are used interchangeably in this guidance.

DPI picker

Choose what you are scanning
A page to keep300 dpi

The Library of Congress says documents should generally be scanned at 300 dpi. That suits most sheets of drawings you just want to keep and look at.

Print it bigger400 to 600 dpi

If you plan to enlarge a small picture to 8 x 10 inches or more, the Library suggests 400 or 600 dpi so there is detail to spare.

Every pencil line600 dpi

For fine pencil work, 600 dpi is a sensible ceiling. The Library notes that anything above 600 may be unnecessary for prints and papers.

An old 35mm slideabout 1900 dpi

Slides are far smaller than prints, so the Library suggests a much higher setting, around 1900 dpi, to get a usable picture.

Settings: Library of Congress personal archiving guidance.

These are starting points for everyday home scanning, not archive standards. A scanner's stated resolution can be higher than the detail it really captures.

TWO NUMBERS WORTH KNOWING

More dots,
much bigger files.

Resolution is a trade-off between detail
and the space and time it costs.

9× the disk space

Three times the resolution

Pixels are counted across and down, so tripling the dpi gives nine times the pixels. Our own rough sum: an A4 page at 300 dpi is about 8.7 million pixels, around 26 MB uncompressed in colour; at 600 dpi it is about 35 million pixels, roughly 104 MB.

FILE SIZE · LIBRARY OF CONGRESS BLOG

~50% on some scanners

Real detail captured

An imaging expert quoted on the Library's blog warned that common scanners may be only 50% efficient, so the number on the box can overstate the detail you get. He doubted consumer scanners improve much above 1200 ppi.

SCANNER LIMITS · LIBRARY OF CONGRESS BLOG

Higher settings also mean slower scans and more storage for every backup. One photographer quoted on the same blog noted that higher resolutions mostly gave him more dust to clean up later.

BEFORE YOU SCAN

Four habits
for cleaner scans.

  • Clean the glass

    Wipe the scanner glass so dust, smudges and specks do not end up in every scan. Brush loose crumbs of crayon or rubber off the drawing too.

  • Take off clips and staples

    Library guidance says to remove paper clips, staples and tape before scanning, so the page lies flat on the glass.

  • Keep one master, share a copy

    Save the best scan as your master file, then make smaller JPEG copies to send to family or post online.

  • Copy it twice, somewhere else

    Keep one copy on your computer and another on a separate drive or online storage, then diary a check in five years.

A neat stack of children's drawings on a desk beside a small plain external drive and a closed laptop
AI-generated image, not a photograph of a real person or place.

SCAN FACTS

Five things worth
knowing first.

A magnifying loupe resting on a crayon doodle of loops, stars and a flower, showing the grain of the paper
AI-generated image, not a photograph of a real person or place.

  1. 300 dpi is the everyday standard

    The Library of Congress says documents should generally be scanned at 300 dpi, and suggests the same for ordinary 4 x 6 and 5 x 7 inch photos.

  2. Enlarging needs more, but not endless more

    For pictures you plan to enlarge to 8 x 10 inches or bigger, it suggests 400 or 600 dpi, and notes that anything above 600 may be unnecessary.

  3. Archives prefer files with nothing thrown away

    The Library's preferred formats for digital photographs include TIFF, JPEG 2000, PNG and JPEG. It prefers uncompressed files and the highest bit depth available, 16 bits per channel where possible.

  4. Light keeps working on the paper

    The Northeast Document Conservation Center says light damage is cumulative and irreversible, and that ultraviolet weakens, bleaches and yellows paper. A scan keeps the colours as they are today.

  5. Storage goes out of date

    The Library recommends at least two copies of your scans in different places, and moving them to current storage about every five to seven years.

QUICK QUESTIONS

Scanning, answered.

Short answers to the questions people ask most.

What dpi should I scan a drawing at?

For a sheet you simply want to keep, the Library of Congress says documents should generally be scanned at 300 dpi. If you want to print a small picture at 8 x 10 inches or larger, it suggests 400 or 600 dpi.

Is a higher dpi always better?

Not always. The Library notes that anything above 600 dpi may be unnecessary for prints and documents. File size grows fast: one expert quoted on its blog says a scan at three times the resolution takes up nine times as much disk space.

Should I save scans as TIFF, PNG or JPEG?

The Library of Congress lists TIFF, JPEG 2000, PNG and JPEG among its preferred formats for digital photographs, with uncompressed files preferred and lossless compression acceptable. Its personal archiving tips say a medium-quality JPEG is fine for everyday colour scans you do not plan to reprint.

How many copies of my scans should I keep?

The Library recommends at least two copies, stored in different places as far apart as practical, and moving your scans to current storage about every five to seven years.

What is FADGI?

The Federal Agencies Digital Guidelines Initiative publishes technical guidelines for digitising cultural heritage. Its star system rates images from 4-star, the highest quality, down to 1-star. The third edition was published on 10 May 2023.

Sources

Where the facts come from

  1. Scanning your collections: resolution and formatsLibrary of Congress
  2. Personal archiving: scanning tipsLibrary of Congress
  3. How many dpi/ppi is too much? (2013)The Signal, Library of Congress
  4. Recommended Formats Statement: still imagesLibrary of Congress
  5. FADGI still image guidelines, third edition (2023)The Signal, Library of Congress
  6. Protection from light damageNortheast Document Conservation Center

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