Start
Previous Next

5. Working with PhotoLine / 5.6 Scanning

### 5.6.3 Resolution, Bit Depth, Document Size

Most scanner drivers allow you to define which kind of image you want to get. They usually offer black/white, gray or color. Note that it is better to scan black/white images with gray because gray allows better editing.

The various additional functions of your scanner driver - like enhancing the contrast or lighten up the image - shouldn’t be used because they modify the image data and you loose image information. Your possibilities to enhance the image afterwards with PhotoLine will be smaller.

The scan resolution value is often set false by users. The motto "the higher, the better" is not true because high resolutions dramatically increase the amount of memory needed by the image, and much memory consumption means slow image processing.

If you want to scan a color picture in order to print it on an ink jet printer, you should choose a scan resolution of 150 to 200 dpi. "dpi" means dots per inch. Of course ink jet printers offer much higher resolutions (600 dpi, 1440 dpi or even higher), but they are not real usable resolutions. They are creating their colors by placing several pixels using basic colors. These basic colors are usually cyan, magenta, yellow and black.

If you want to print the scanned image enlarged, you have to multiply the proposed resolution with the scale factor.

On printing black/white images the above color problem doesn’t exist. Therefore, you should scan in printer resolution.

Scan resolution (color images) = scale factor * 150 dpi

Scan resolution (black/white images) = scale factor * printer resolution

You should always keep in mind, that scanning can create enormous amounts of data. These data can be too much for your computer.

To calculate the memory used by a scan, you can use the following formula:

Size in bytes = (width in cm / 2.54) * (height in cm / 2.54) * resolution * resolution * 3