The fastest way to improve OCR accuracy is to improve the image before recognition starts: sharp focus, even light, a straight page, dark text on a clean background and the correct language setting. OCR software can only read what the picture shows clearly. If you capture paper with the PDFNova Camera Scanner and then run OCR PDF with the right language, most everyday documents come out with far fewer errors.
The ten tips below are in rough order of impact. The first five are about the scan, the next three are about settings and the last two are about checking the result.
10 tips to improve OCR accuracy
1. Start from the best source you have
If you have the paper, scan the paper. If you have the original photo, use it and not a copy that was forwarded through a chat app, because forwarded images are often shrunk. A photocopy of a photocopy, or a screenshot of a scan, loses detail at every step.
2. Get sharp focus
Blur is the largest single cause of misread letters. Clean the camera lens, rest your arms on the table, wait for the camera to focus and hold still while capturing. Zoom in on the result. If the edges of letters look smeared to you, retake it.
3. Use even light with no shadows or glare
Daylight from a window is ideal. Stand so your phone and hand do not shade the page. Avoid flash on glossy paper, since a white glare spot erases the words under it. A dark corner of the page will be read worse than the bright centre.
4. Keep the page flat and straight
Curved or tilted lines are harder to follow. Flatten folds, press book pages down near the spine and hold the camera parallel to the paper. In the Camera Scanner, check that the corner points sit on the real corners of the page so perspective correction can square it properly.
5. Fill the frame with the text
Small letters need enough pixels. Move closer so the page fills the screen, and capture one page at a time, not two side by side. For very small print such as footnotes or the back of a form, capture that area as its own page.
6. Choose the right filter
The black and white filter gives strong contrast and suits clean printed text. On faded, stained or tinted paper it can break thin strokes or turn stains into black marks. In those cases grayscale usually reads better. Try one page both ways and compare.
7. Select the correct language
This setting matters more than people expect. OCR PDF supports English, Urdu, Arabic, Hindi, French, Spanish, German and Chinese (Simplified). Choosing the wrong one produces nonsense even from a perfect scan. For a document in two languages, run it with the main language and correct the rest by hand.
8. Turn pages the right way up
Sideways and upside-down pages are a common reason for empty or garbled output. Fix the orientation with Rotate PDF and save the file before you run recognition.
9. Process difficult pages separately
One bad page in a long file is easier to fix on its own. Use Split PDF to take out the weak pages, rescan or adjust them, and run them again. The same idea helps with multi-column pages: crop or scan each column separately if the reading order comes out mixed.
10. Proofread what matters
No OCR is perfect. Read the output against the image, and check every number, date, name and reference code character by character. Typical confusions are the letter O and zero, lowercase l and the number 1, and the letters rn read as m.
A reliable scan-then-OCR workflow
- Place the page on a dark, flat surface near a window.
- Open the Camera Scanner and allow camera access when the browser asks.
- Capture the page, then adjust the corners if automatic edge detection missed an edge.
- Choose black and white for clean print, or grayscale for faded paper, and add any further pages.
- Save the pages as one PDF.
- Open OCR PDF, add that file and select the language of the document.
- Run recognition. Language data downloads the first time a language is used.
- Copy the text, download a .txt file or download a searchable PDF, then proofread.
Match the error to its cause
| What you see in the output | Likely cause | What to change |
|---|---|---|
| Random symbols everywhere | Wrong language or rotated page | Set the language, rotate the page upright |
| Many single-letter mistakes | Blur or low resolution | Rescan closer and steadier, use the original image |
| Missing words on one side | Shadow or uneven light | Move to even light and rescan |
| Missing patch in the middle | Glare from flash or a lamp | Change the light angle, turn off flash |
| Broken, incomplete letters | Filter too harsh for faded print | Switch from black and white to grayscale |
| Lines from two columns mixed | Complex layout | Process each column or section separately |
| Stray dots and marks as characters | Stains, creases, punch holes | Flatten the page, crop out the margins |
What OCR still struggles with
Good technique raises accuracy, but some material stays hard. It helps to know the limits so you can plan the time for corrections.
- Handwriting. OCR is built mainly for print. Joined or hurried handwriting gives weak results however good the scan is.
- Decorative and very small fonts. Stylised headings, calligraphy and tiny legal print are often misread.
- Text over images. Words on photos, watermarks and colored panels are frequently skipped.
- Tables. The words are found, but the row and column structure is not kept in plain text.
- Connected scripts. Urdu Nastaliq is harder than printed English because of its sloping, stacked letter shapes.
Language-specific advice
Each script has its own difficulties, such as dots and diacritics in Arabic or the headline bar and conjunct letters in Hindi. We cover them one by one in Arabic OCR online, Hindi OCR online and Urdu OCR online. In all three, larger text and higher contrast help even more than they do for English, because small marks carry meaning.
Frequently asked questions
Why is my OCR result so inaccurate?
Usually because of the image: blur, shadows, a tilted page or small text. The second most common reason is the wrong language setting.
Does black and white or color scanning give better OCR?
Black and white is best for clean printed pages. Grayscale is safer for faded, stained or colored paper where black and white would destroy thin strokes.
Can OCR be completely accurate?
Do not expect it. Clean printed pages can come very close, but you should always proofread important text, especially numbers.
Does a bigger image always help?
More detail helps up to the point where letters are clearly formed. Beyond that, a larger file mainly makes processing slower.
Better input gives better text. Rescan your most troublesome page with these tips, run it through OCR PDF again and compare the two results.