Precautions in OMR Sheet Scanning

1. Proper Placement of Sheets in the Scanner

• Place OMR sheets carefully in the scanner tray or document feeder.

• Ensure sheet holding brackets are properly adjusted to avoid the sheets from straying, tangling, or tilting.

• Although Addmen OMR Software can read rotated, skewed, or slightly distorted sheets, proper alignment reduces errors and speeds up scanning.

2. Scanner Settings and Adjustments

• Do not increase brightness or contrast unless explicitly guided. Scan at default settings.
• Keep the scanning area wide enough to capture all corner index points and sufficient white space around them.
• Scanning Mode Guidelines:

  • Black & White (1-bit): For regular OMR sheets without images. Minimizes file size and speeds up processing.

  • Color (RGB): For sheets with photos or two-color printing. Ensures clarity of photographs or colored bubbles.

  • Minimum 150 DPI: Required if the sheet contains OCR fields, barcodes, or photographs.

3. Correct Output File Format

• Save scanned images as JPG, TIFF, or BMP only.
• Do NOT save as DOC or PDF — OMR software cannot read these formats.
• When using TIFF format, ensure single-page TIFFs are created (one file per OMR sheet). Avoid multi-page TIFFs, which combine multiple sheets into a single file.

4. Influence of Scanner on Accuracy

Even with correct scanning procedures, the scanner itself can affect image quality:

1. Pencil Marks and Glare:

   • Some scanners fail to capture faint pencil marks due to glare or light angle, resulting in rarified impressions.
   • The OMR software reads the scanned image, not the paper; if the mark is missing or faint on the image, accuracy suffers.

2. Old or Worn Scanners:

   • Aging scanners may have worn drag rollers, producing skewed or distorted images.
   • Slight skew is tolerated by OMR software, but excessive or uneven distortion requires scanner repair or replacement.

3. Wobbling Rollers:

   • Some scanners stretch or compress parts of the sheet along its length, affecting bubble dimensions.
   • These internal distortions are scanner defects, not user errors.

Tip: If output quality is suspect, scan the same sheet on another scanner and compare results to identify scanner-related issues.

5. Summary of Key Precautions

Table

Step	Best Practice
Sheet Placement	Adjust holding brackets; avoid tilting or tangling
Scanner Mode	B/W (1-bit) for normal sheets; RGB for colored/photos; 150+ DPI for OCR/barcode
Scanning Area	Include all 4 corners and timeline with sufficient white space
File Format	JPG, TIFF (single-page), BMP; avoid DOC/PDF
Scanner Maintenance	Ensure rollers are functional; replace or repair old/worn scanners
Accuracy Check	Scan sample sheets on a different scanner if image quality is inconsistent

 

By following these precautions, scanning accuracy improves significantly, and the OMR software can read sheets reliably without requiring specialized hardware.

Table

Read more:

• OMR Scanning- Overview - Specifications - Precautions
• OMR Scanning- Coloured - Barcode
• OMR Scanner- Models and Price
• Download- Sheet Scanning Guide

Related Links:

• OMR Sheet Design- Overview - Process - Basic Features - Advance Features
• OMR Printing- Overview - Guidelines - Precautions - Methods