Chapter 2. Scanning Concepts

2.3 Resolution and Sizing
Depending on the contents of your documents, basically, we can classify them into three image types.

2.3.1 Resolution
Resolution determines the level of detail recorded by the scanner.
Image quality will improve with higher resolution, but after a certain point, what we called "optical resolution", it won't get any visible improvement to the image even with increase resolution.

The difference between "optical resolution" and "maximum resolution"?

  • Optical resolution is the "native" resolution of the scanner, determined by the optics of the scanner hardware( for example: 300 x 600 dpi scanner, 300 dpi is the x-coordination resolution determined by CCD (Charge-Coupled Device) and 600 dpi is the y-coordination resolution determined by the steps of motor per second).
  • Maximum resolution is the resolution enhanced through interpolated algorithm. Interpolated resolution is useful in scanning line art or enlarging small originals, however, maximum resolution is inferior to optical resolution in some image quality and crispness.
  • 2.3.2 Image Size
    A large image size could lower the system performance of your computer dramatically. The file size is affected by the selected area, file format, scaling percentage, resolution and the image type. Please refer to the following table (file compression is excluded):
    Image Type Description Image Size (Bytes)
    1-bit images Black and White Line Art or Halftones (Height x Width x Height resolution x Width resolution) x (Scaling percentages) 2 /8
    8-bits images Black and White or Color Photo, 256 gray levels or 256 colors (Height x Width x Height resolution x Width resolution) x (Scaling Percentages) 2 x 8 ) /8
    24-bits images Color Photo, Millions of Colors ((Height x Width x Height resolution x Width resolution) x (Scaling Percentages) 2 x 24 ) /8
    30-bits images Color Photo, Billions of Colors ((Height x Width x Height resolution x Width resolution) x (Scaling Percentages) 2 x 30 ) /8