Scan Quality Tips for AI Transcription: Get the Best Results

AI-powered tools like GermanLetters can read old German handwriting with remarkable accuracy. But here's what many people don't realize: the quality of your scan or photo affects the transcription just as much as the AI itself. A blurry image, shadows on the page, or heavy grid patterns can significantly reduce accuracy. This article explains exactly which factors matter and how to prepare your documents for the best results.

Why Image Quality Matters So Much

An AI doesn't read like a human. It analyzes pixels to identify patterns — letter shapes, spacing, stroke direction. Anything that obscures or distorts those patterns forces the AI to guess, which increases uncertainty. A human can mentally "see through" a shadow or ignore grid lines; an AI is more directly affected by visual noise than you might expect.

The Most Common Quality Issues

Low Resolution and Pixelation

When an image is too small or heavily compressed, fine strokes blur together. In Kurrent and Sütterlin, the difference between "e," "n," and "u" comes down to tiny details — a pixelated image erases exactly those distinctions. Recommendation: Scan at 300 DPI minimum. For faded or very fine handwriting, use 400–600 DPI. Smartphone photos work well if the text appears sharp and fills the frame.

Shadows and Uneven Lighting

Shadows are one of the most common quality killers. A lamp on one side creates bright and dark zones — the AI loses contrast in the shadowed areas and reads less reliably. Recommendation: Use diffused, even lighting. Overcast daylight works perfectly. Avoid direct sunlight or single-source lamps. Flatbed scanners eliminate this problem entirely with built-in even illumination.

Tilted Pages and Perspective Distortion

If the document is skewed or photographed at an angle, letters become distorted and lines aren't horizontal. Even a 15-degree tilt can noticeably reduce recognition accuracy. Recommendation: Hold your camera directly overhead. Place the document flat. A slight angle is fine, but avoid steep perspectives. Scanner apps can auto-correct minor tilt.

Grid Patterns and Lined Paper

Many old diaries and notebooks use lined or grid paper. The AI can confuse grid lines with pen strokes, especially when the grid is dark relative to the ink. Recommendation: Maximize contrast between ink and background. Some scanner apps offer a "document" mode that brightens the background and emphasizes the writing.

Faded Ink and Yellowed Paper

Decades of aging can fade ink and yellow paper, reducing the contrast the AI relies on. Recommendation: Scan in color rather than black-and-white — this preserves more visual information for the AI to work with. Slightly increasing contrast in an image editor can help, but don't overdo it.

The Ideal Scan Checklist

For optimal results with GermanLetters: Resolution of 300+ DPI. Even lighting with no shadows. Page straight in the frame. Clear contrast between ink and paper. PNG or high-quality JPEG/PDF format. The page fills most of the image. For old, yellowed documents, scan in color.

Not every document can be scanned under ideal conditions — and that's okay. GermanLetters's AI is trained to handle imperfect images. But the better your source image, the better your transcription will be. For more on digitization techniques, see our guide on how to digitize old letters for transcription. Ready to test? Upload your first pages free at GermanLetters.