Clear scans make recognition and human review easier. Image quality affects whether a page can be processed and how well its answers can be read.
Minimum requirements
Resolution alone does not determine whether a page can be processed. Keep the full page, alignment marks, identifiers, and answer areas visible. Blurry, faint, or cropped scans can fail processing or produce incorrect readings, including readings that are accepted automatically.
Recommended resolution
300 DPI is the recommended starting resolution. Test several completed forms and compare the recognized answers with the originals before scanning a full batch.
| Resolution | Result |
|---|---|
| 300 DPI | Recommended starting point; check a sample of results |
| 200 DPI | Test that marks and handwriting remain clear |
| 150 DPI or below | Higher chance of recognition errors |
| Above 300 DPI | Larger files; compare a sample before using for a full batch |
What affects quality
Beyond resolution, these factors impact recognition accuracy:
- Print quality - Surveys printed on a good laser printer produce clearer marks than inkjet prints
- Photocopies - Photocopied surveys lose some detail but are still readable. See Can Paper Surveys Be Photocopied?
- Pen choice - Black or blue pen produces the most consistent marks
- Page condition - Wrinkled, folded, or stained pages may cause issues
- Scanner cleanliness - Dust or smudges on the scanner glass appear on every page
Smartphone photos
Photos taken with a smartphone camera can also be processed, though they typically have lower quality than flatbed scans. For best results with phone photos, ensure good lighting and hold the camera directly above the page.
When quality is too low
Check the Uploads page for processing errors or skipped pages, and compare the processed page count with the batch you submitted. Re-scan unreadable pages with better lighting or scanner settings. For pages that did process, review flagged responses and a sample of accepted answers against the originals.