Applies to: Paper scanning modes. Bit depth comparisons describe raw samples, not final compressed file sizes.
Use color when color carries meaning, grayscale for faded text, handwriting, stamps, or photographic content, and black-and-white only for clean, high-contrast printed pages. When unsure, grayscale is the safer document setting.
Black and white is not grayscale
Black-and-white, sometimes called bitonal or monochrome, records each pixel as one of two values. Grayscale records many brightness levels. Color records separate channels, usually red, green, and blue.
Bitonal scanning can create very small files, but thresholding may erase faint pencil, light signatures, paper texture, and thin punctuation. Grayscale preserves those transitions with less data than full color.
Match the mode to the information
- Clean typed text on white paper: test black-and-white at 300 to 600 PPI.
- Faded copies, handwritten notes, stains, or halftone pictures: use grayscale.
- Colored annotations, seals, highlights, maps, or photographs: use color.
- Continuous-tone black-and-white photographs: use grayscale, not bitonal.
- Uncertain or mixed pages: capture a grayscale or color master and create smaller access copies later.
Think beyond appearance
A yellow highlight may be nearly invisible after grayscale conversion even when the text remains readable. Red and green annotations can collapse to similar gray values. If color distinguishes status, author, or meaning, retain color.
For OCR, clean contrast and straight pages matter as much as color mode. A sharp 300 PPI grayscale scan may recognize better than a noisy 600 PPI color scan.
Compare one difficult page
Choose the faintest or most complex page in the batch and scan it in two candidate modes. Inspect small text, decimal points, handwritten additions, stamps, and shaded tables.
Keep the mode that preserves all meaningful information. File size can be reduced later; missing source detail usually cannot be recovered.
Compare what each mode discards
At equal pixel dimensions, a one-bit scan records two levels; an eight-bit grayscale scan records up to 256 levels; a typical 24-bit RGB scan records three eight-bit channels. Before compression, RGB uses three times the sample bytes of grayscale and 24 times those of one-bit data.
File size alone cannot select the mode. Use a sample containing a faint pencil mark, a light highlight and a decimal point. If a mode removes any item that changes meaning, reject it even when OCR still recognizes most words. Preserve the better master and create a smaller sharing copy separately.
Sources and further reading
Vendor instructions and background references are linked below. Worked examples are our explanatory calculations, not vendor performance claims. Check the instructions for your current software and device.
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