Evaluating the quality of a scanned image involves examining several technical and visual aspects. Here are some criteria to consider:
✨ Resolution (DPI - Dots Per Inch)
The resolution of a scanned image is measured in dots per inch (DPI). The higher the resolution, the more detailed the image. For text documents, a resolution of 300 DPI is usually sufficient, while for images or photographs, 600 DPI or higher may be necessary.
✨ Sharpness
Sharpness refers to the clarity of details in the image. A well-scanned image should have sharp, distinct edges without excessive blurring. Blurring can be caused by movement during scanning or incorrect settings on the scanning device.
✨ Color and Contrast
The colors of the scanned image should be faithful to the original. The contrast should also be sufficient to distinguish light and dark details without losing information. Dull colors or low contrast may indicate poor scanner calibration or improper settings.
✨ Presence of Artifacts
Artifacts are unwanted defects in an image, such as lines, specks, digital noise, or moiré patterns. These can be caused by poor equipment quality, dust, or scratches on the scanner glass.
✨ Aspect Ratio and Distortion
The scanned image must maintain the correct proportions of the original. Distortion can occur if the document is not placed correctly on the scanner or if the scanner is poorly calibrated.
✨ Grayscale
For grayscale documents, it is essential that the scanned image captures a full range of grays, from deep blacks to bright whites, without loss of detail in shadows or highlights.
✨ File Size
A high-quality scanned image with high resolution and good color will typically have a larger file size. However, it is important to balance quality with file size for storage and sharing needs.
✨ Lighting Uniformity
A well-scanned image should show uniform lighting, with no areas that are too bright or too dark. Variations in lighting can indicate problems with the scanner or misalignment of the document.
✨ Color Depth
Grayscale Images: Often used for text documents, a color depth of 8 bits per pixel (256 levels of gray) is standard.
Color Images: For high-quality color images, a color depth of 24 bits (8 bits per channel for red, green, and blue, totaling 16.7 million colors) is typical.
Medical and Scientific Images: Some applications require a color depth of 16 bits or more per channel to capture a wider range of detail and nuance.
✨ File Formats
JPEG: Used for photographs and images on the web, it offers good lossy compression, but reduces quality by discarding some data.
TIFF: Used for scanned documents and photographs, this format can be lossless and is therefore preferred for maximum quality.
PNG: Used for images on the web where transparency is required, it offers lossless compression.
DICOM: A standard for medical images, including X-rays, CT scans, and MRIs, this format retains the metadata needed for accurate diagnosis.
✨ Compression Standards
JPEG 2000: An improved version of JPEG that allows for lossy and lossless compression, often used in digital archives and for medical images.
HEIF (High Efficiency Image Format): Used to compress images while maintaining high quality, often used by modern smartphones.
✨ Visual Quality Standards
ISO 12647: A series of international standards for printing processes that specifies quality criteria, including color density and gamut.
sRGB and Adobe RGB: Standard color spaces used to ensure the faithful reproduction of colors on different devices. sRGB is widely used for displays and on the web, while Adobe RGB is used in professional environments for a wider color gamut.
✨ Color Calibration and Consistency
ICC Profiles (International Color Consortium): ICC profiles are used to ensure consistent color reproduction between different devices (scanners, displays, printers).
ISO 3664: Specifies lighting conditions for color evaluation, which is essential for industries where color accuracy is critical.
ADOC Solutions teams support you in managing your documentary processes.
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