10 ways to get more accurate OCR from scans and photos

OCR accuracy depends far more on the image you give it than on the software. These ten habits make the biggest difference.

Scanning

1. Scan at 300 dpi. It's the best balance between detail and file size. Go up to 400 dpi for small print or dense scripts like Devanagari, Bengali or Malayalam. Higher than that rarely helps.

2. Use greyscale or black and white, not colour. Colour adds file size without helping OCR. For faint originals, greyscale keeps more detail than pure black and white.

3. Scan the original, not a photocopy. Every generation of photocopy loses fine strokes: dots, accent marks and vowel signs are the first to go.

4. Keep the page flat and straight. Close the scanner lid fully. For books, press the spine down gently; curved lines near the binding are a common source of errors.

Phone photos

5. Shoot straight down, in even light. Hold the phone parallel to the page. Avoid your own shadow, and avoid flash, which causes glare on glossy paper. Daylight near a window works well.

6. Fill the frame with the page. Get close enough that the page fills the photo, but keep all four corners in view. Use a scanning app's crop and "document" mode if you have one.

7. Check sharpness before you move on. Zoom in on the photo. If you can't read the small print clearly, the OCR won't either.

Settings

8. Choose the right language. This matters more than people expect. With the wrong language, OCR guesses using the wrong alphabet and vocabulary. For bilingual documents, select both languages (Docuflat allows up to three). Choose Marathi rather than Hindi for Marathi text, and Assamese rather than Bengali for Assamese, even though the scripts look alike.

9. Convert only the pages you need. Split out the relevant pages first. You'll get results faster and use less of your daily OCR allowance.

Afterwards

10. Proofread numbers, names and dates. OCR most often confuses similar-looking characters: 0 and O, 1 and l, 5 and S, and in Indian scripts, letters that differ only by a small stroke. Check anything you'll rely on against the original.

What OCR can't do well

Even with perfect technique, some things remain hard:

• Handwriting, especially joined-up writing
• Text on top of stamps, seals or watermarks
• Decorative and calligraphic fonts
• Very old printing with broken or faded letters

For these, OCR gives you a starting point, but plan to correct the output by hand.