Scanners

Scanner manufacturers represent the fixed, optical resolution of their products with two numbers: 1200 x 2400 dpi for example.

In this case 1200 would be the number of sensors that are positioned horizontally in the scanner head and 2400 would be the number of steps the carriage motor can take as it travels one inch down the film or document being scanned.

When they claim that their scanner has a maximum resolution of 9600 dpi they are describing the amount of information the scanner software can interpolate, or fake.

Digital image pixels that are created by scanners can be many different sizes depending on how many slices, or "samples," the scanner divides the image into. For example, a 300 sample per inch (spi) pixel is 1/300th of an inch wide. A 1 spi pixel is one full inch wide!

Scanners usually refer to the image pixels they create as dots per inch or dpi because, just like camera sensors, the scanner is recording visual information that is intended to be rendered as dots of pigment on the surface of photographs created by an ink jet printer.

One other measure of a scanner's quality is its density range. This describes the amount of contrast the scanner can record and the higher this number the greater the scanner's ability to render detail in the shadow areas. Density range numbers above 3.2 are very good.

Digital Cameras For Beginners

Digital Cameras For Beginners

Although we usually tend to think of the digital camera as the best thing since sliced bread, there are both pros and cons with its use. Nothing is available on the market that does not have both a good and a bad side, but the key is to weigh the good against the bad in order to come up with the best of both worlds.

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