Scanning The Technical Information

by Rob Fraser, Systems Support Engineer

There has always been a misconception that more is better. But in the case of scanning text and pictures, that rule does not always hold true.

Though you can use image-editing programs to change image properties or to enhance image quality, you would almost always get better results from scanning at lower resolution directly, than re-sampling a high-resolution image by software afterwards.

For example, comparing two 100x100 pixel images scanned from the same 1" x 1" picture – one is scanned at 100 dpi, the other is scanned at 200 dpi (200x200 pixels) then re-sampled down to 100x100 pixels by software. The former would appear much sharper than the latter in most circumstances, plus by scanning at lower (100 dpi) resolution, it would help save disk space to save the image and also cut down the actual time required by the computer to scan and process the image.

For instance, if the image is scanned for displaying on screen, as for Web Publishing, slideshow, wallpaper and the like, due to the 1-to-1 pixel mapping from an image to monitor display, you should select a scanning resolution accordingly to the monitor resolution. One approach is to scan at the monitor resolution - 72 dpi to 96 dpi, this would maintain approximately the same physical dimensions of the image on screen and its original (a 4" x 6" photo would still be measured 4" x 6" on screen).

The other approach is to determine the outcome pixel dimensions of the image first, then calculate the scanning resolution according to the size of the original. For example, if you like to scan a 3" by 2" image and to keep it displayed within one screen on most monitors, the ideal pixel dimensions would be 600 x 400 pixels (keep in mind that a VGA monitor is set to display 640 x 480 pixels per screen). Therefore the ideal scanning resolution should be 200 dpi (600/3).

To send out an image to a fax machine, scanning at 200 dpi to 300 dpi in B&W (Line Art) mode would create the best results.

But if you want to print an image, what would be a good scanning resolution?

The problem is that the printing technology hasn’t quite caught up with the scanning technology. The stated maximum resolution of a printer is several times larger than the image resolution it can actually print out.

Scanning The Easy Way - The Recipe For Success:

File Size = 200x200 pixels

Colour = B&W

The perfect tasty scan every time! Remember smaller is better.
rob.fraser@financial.ltd.uk