.Tech help that's really helpful!
Created: 27 May 1999 ::: Last updated: 01 May 2007
Applies to:
X Win95
X Win98
X WinMe
X Win 2000/NT
X WinXP
_ WinVista
_ MacOS
By Andy Walker
Question: I recently purchased a 36-bit 600x1200-dpi scanner. I also have a Canon BJC-4200 printer with a maximum print quality of 720x360-dpi and am using Windows 95. After adjusting many settings on my computer, printer, and the scanner, I am not satisfied with the product. At this stage, I am very confused. Is it the computer, the scanner, the printer, or is it me? Could you suggest the minimum capacity of each item in order for me to get a satisfactory product? - Daphne
Answer: Scanners have become household appliances for some people, but there's still a little bit of science you need to know to get the great results you had in mind when you bought yours.
First of all, you shouldn't attempt to do any scanning on an under-powered computer. Pictures require lots of storage space and a fair amount of memory processing.
You don't say what you're dissatisfied with, but I bet it's the image quality. If you're expecting photo quality output on an inkjet printer, you’ll probably be disappointed. If you're scanning a picture at 600 x 600 dots per inch and printing it on the printer you have mentioned, you're going to get a print-out at only the maximum resolution of your printer.
Think of each dot as a tiny piece of a photo that the scanner examines. The more pieces of a photo that a scanner can detect, the more detailed it will be, and the higher the resolution of the scanned image will be, so the sharper its appearance should be.
The resolution on most scanners for sale today ranges around 600 dpi and up. If the scanner has 600 sensors per inch on the scan head, which moves across a scanned image, the resolution would be specified as 600 x 600 dpi. Sometimes, scanner makers claim their scanners are 600 x 1,200 dpi if the scan head pauses at each "dot" and takes two pictures of it.
When buying a scanner, be aware that manufacturers may refer to two different kinds of resolution. "True" or "optical" resolution means the actual dots-per-inch measurement that is physically possible with the scanner. Some scanners claim a higher dpi than is physically possible. This is called "interpolated" or "enhanced" resolution. This is achieved because the scanner has hardware or software built in that makes a best guess at what is between the dots that it can't "see".
To figure out the best resolution to scan an image, you need to know the halftone line screen resolution used for the final output on paper. A halftone is the method used to put images on paper. If you look at a newspaper picture closely, you'll discover it is made up of tiny inky dots. This is a halftone and its resolution is measured in lines per inch, not dots per inch. An image printed on a 300 dpi inkjet printer or 600 dpi laser printer would only use a line screen of 80 lpi to 105 lpi. The scanning resolution you'd need, in most cases, would be close to twice the line screen resolution of your final output. Output to a laser printer or inkjet printer would be 160 to 210 dpi and that would be fine.
If you want to enlarge the image, the scanning resolution corresponds to the percentage of enlargement. If you intend to scan a photograph of your dog Rufus and then print it on a 300 dpi printer that has a line screen resolution of 100 lpi, double the 100 lpi and scan at 200 dpi. If you plan to print the image at 200 per cent of its original size, you need to double the scanning resolution to 400 dpi.
Here are some more resources you can check:
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