Scanning is a great way to capture and archive images as well as a great way to get a high-quality version of an image. Many scanners can capture images with resolutions from 1200-9600 PPI! It is important that when scanning images, you use the correct settings. Below are some tips for scanning images:
Make sure that images are clear of any dust or debris by gently wiping them with a dry cloth. Also, make sure that the scanner glass is clean before scanning to ensure that the quality of the scan is at its highest and also to protect your images.
Whenever possible, scan from an original print. Sometimes when scanning images from magazines or other prints, we pick up unwanted printing information, such as ink dots, that can become visible when scanning at a high resolution. [Shown Below]
Obviously if your image is in color, then you will select to scan in color, however, it is sometimes hard to know when to choose B&W or Greyscale. B&W works very well for line art or sketches, but choose greyscale when your graphic has shades of gray as well as black and white. Greyscale scanning will record up to 256 shades of grey, and so the transition from white to black is smooth. This is the best choice for black and white photos. With greyscale images, each pixel can store one of 256 different shades, making greyscale images much larger than line art.
The resolution at which you scan your image will depend on the end use of that image. Will it be for the web or a presentation or will it be enlarged and printed? Use this handy Resolution/Print calculator to determine at which resolution images should be captured.
If you're unsure which type of file would be best for your scan, check out this page that explains Image File Types.
It is recommended to make some edits or touch-ups to a scanned image. Some recommended touch-ups include: cropping and straightening, correcting any color casts, and removal of dust and scratch marks.
Moiré effect is a visual perception that occurs when viewing a set of lines or dots that is superimposed on another set of lines or dots, where the sets differ in relative size, angle, or spacing. Moiré effect can produce interesting and beautiful geometric patterns. However, the phenomenon degrades the quality and resolution of graphic images. (from WhatIs.com)
Example of a Moiré pattern