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32-Bit or Bust
If your scanner doesn't have 32-bit driver support by now, get on the manufacturer's case! Almost every scanner maker now provides 32-bit Windows 95-compatible drivers for their scanners, and many also provide Windows NT drivers.
Set the Tonal
When you're testing a scanner to determine its tonal range by scanning a piece of sample artwork or a photo target, make sure you set the scanner's tonal output to prevent clipping of the image's histogram. Most scanners have a tonal range setting, usually 0-255 on each channel, that can be used to adjust the resulting signal sent back to the computer. Set each channel's tonal range to 5 minimum and 250 maximum to prevent clipping and ensure a proper calibration.
When scanning images that you will eventually convert to vector images through a tracing program, try lowering the image threshold or increasing the brightness to decrease the amount of spurious detail. What looks good for a bitmap doesn't always work as well for a raster-to-vector conversion. You might also try applying despeckling filters before tracing to remove stray dots.
Some SCSI scanners don't like to talk to anything other than a 100 percent Adaptec-compatible SCSI card, and act strangely with others. If you're buying a scanner to operate with a SCSI card you already own, talk to the manufacturer and determine if it supports your card. Also, make sure you're not going to pay extra for a bundled SCSI card you're not going to use.
No Bad Vibes
If you've got a scanner and a printer on the same workstation, try not to put them right next to each other, especially if you tend to use both at the same time. Vibrations from the printer can cause scans to come out blurred or unfocused.
RGB or CMYK?
When scanning in a new image, some TWAIN drivers give you the choice of rendering the image as CMYK or RGB. If you'll ultimately use CMYK as your output model, you may want to stay with RGB and convert to CMYK or (CIE Lab-model color) after the fact. Also, the RGB-to-CMYK conversion algorithms in different TWAIN drivers may not produce symmetric results, if you're deriving input from more than one scanner.
Both the lens and the glass in scanners need periodic cleanings. Some scanners come with pre-moistened appliquettes for cleaning the lens and glass. You can also use a chamois cloth or Tyvek and some isopropyl alcohol.
For the best results when scanning line art, scan in high-resolution grayscale mode. This way, the smoothness of curves and the crispness of lines can be preserved without the image looking jagged.
If you think your scanner's focus may be off, try scanning a piece of graph paper at the optical resolution of the scanner in full-color mode. Using an image-editing tool, zoom in on the edges of horizontal and vertical lines to see if there are blue and red fringes at the edges of lines-a sign of a scanner that's either improperly calibrated or simply not up to snuff. This is also a good in-store test for trying before you buy.
The Ol' Switcheroo
Don't be fooled by the smooth performance of 32-bit scanner drivers in Windows 95 and NT. That doesn't mean you can switch away during a scan to do other things. Experiment a little to see if this is safe. Some TWAIN drivers react badly to the CPU being taken by other programs, and images come out distorted and corrupted.
Work Better with Batches
If you're planning to OCR scanned text from a page with tinted or color areas, scan each colored area separately with different threshold and brightness levels. If your scanner does batch jobs-scanning several different areas on the same images with different settings for each-this is a perfect way to put it to use.
Back It with Black
Sometimes scans on thin paper can cause material on the other side to show through. Put black construction paper behind the image and lower the threshold or increase the brightness to compensate; what you'll lose in terms of image fidelity is negligible compared to the cleanness you gain back.
Don't waste processor time, scan memory and disk space by scanning an image at way above what your ultimate output resolution is going to be, unless you're trying to deliberately down-sample a larger image. Most scanners slow considerably at above 600dpi, especially since the TWAIN driver is doing software interpolation to obtain the image.
Profiles in Scanning
Windows NT scanner drivers take advantage of NT's versatility. With NT 4.0, you can create a hardware profile that has the scanner driver enabled or disabled. That's useful if you want to boot the system with the scanner off (without error messages about drivers not starting properly), or just want to be able to save that much more RAM.
Many TWAIN drivers now come with a descreening function, an algorithm
that removes the mesh-like artifacts that appear when you scan
a photo-offset image. Some of these algorithms are not that good,
and for comparison's sake you may want to try scanning the image
at a very high resolution, then despeckling the image and downsampling
it to a smaller size. Despeckling filters are included in Adobe
Photoshop and in Paint Shop Pro.