What is resolution?
The word “resolution” has multiple applications. In terms of an image for web, resolution describes the level of detail and can be expressed as the total number of pixels contained within an image, or a ratio of pixels per inch (PPI). 72 PPI is the standard level of detail for web images. In terms of a monitor, or display, resolution is the number of pixels that can be displayed on screen, usually given as a ratio of columns to rows (ie: 800×600, or 1024×768).
Resolution, or ultimate sharpness, is the measure of the ability of a spotting scope or binocular to distinguish fine details. Optical glass is at its sharpest in the center, while resolution decreases toward the edges in relationship to the quality level of the lens. Larger objective lenses (with quality as a constant) tend to improve resolution. This is because they have a larger amount of sharp, center objective lens area, as opposed to the amount of lesser sharpness at the edge of the lens surface.
Your scanner converts an image into a number of adjacent “pixels”, or individual dots of color. The greater the density of these pixels, the more detail that can be seen on the final image. This is “resolution” and is measured in “Dots per Inch”, or “dpi”. That’s why the salesman talked you into getitng the highest “dpi” scanner available, right? Guess what? Unless you are going to do extreme closeups of very small areas, or are preparing images for print, you won’t need all that resolution! I don’t think I have ever made a scan of a stamp or cover at greater than 800 dpi, and that was not an entire stamp, just a small detail I wanted to show.
