Today the Internet has thousands of sites offering free images
and clipart. You can't walk into a computer or office supply store
and miss the dozens of inexpensive clipart collections lining the
shelves. But there comes a time when you need to scan an image
for a Web site. You may need to scan a photograph, or maybe part
of a newspaper, magazine or brochure.
I found myself in that predicament several months ago when I
was designing a Web site for a golf course. They wanted their
score card online. A golf scorecard is basically a floor plan
of all 18 holes on a course. The only way to transfer each hole
was using a flatbed scanner. I did some research online and made
a trip to CompUSA.
There was a time when a cheap flatbed scanner cost over $5000.
Fortunately, we've come along way from those stratospheric prices.
Today scanners run from under a hundred dollars to as much as
$2000. Having forgotten the number to my secret Swiss bank account
I leaned toward the low end. But settling for inexpensive doesn't
have to mean surrendering quality.
I wanted a scanner capable of 600 dpi (dots per inch) resolution
and an 8.5" x 14" scanning bed. Although scanners can scan up
to 42-bit using proprietary technology, 30-bit is all you really
need. Resolutions above 600 dpi are also overkill if you are scanning
for the Web only. Scanners come in Parallel, USB and SCSI flavors.
Firewire configurations are also becoming available. I chose a
Parallel port. It's slower but I didn't plan on doing a lot of
scanning. I won't go into the details of installing and configuring
the scanner. The setup is fairly painless and I was doing a test
scan within fifteen minutes of opening the box.
Scanning Tips
Here are some scanning tips for Web designers wanting to import images into
their Web sites.
Choose an Optimum Scanning Resolution
Monitor output is limited to 72 dpi so there is no need to scan at the maximum
600 dpi. I would never go beyond 100 dpi. There are a couple reasons why
you should follow this rule. First, a 600 dpi scan will take longer than
a 100 dpi scan. Secondly, all that extra image quality will be lost on a
72 dpi monitor. The third and most important reason is file size. Below are
the sizes for four full color scans of a 1 x 1 inch image (these sizes are
before compression). 72 dpi - 72 x 72 = 1440 pixels (approx. 4.3k) 100 dpi
- 100 x 100 = 10,000 pixels (approx. 30 kb) 300 dpi - 300 x 300 = 90,000
pixels (approx. 270 kb) 600 dpi - 600 x 600 = 360,000 pixels (approx. 1 Mb)
As you can see, a 600 dpi image scan is over 30 times larger
than a 100 dpi scan.
Here is a simple formula to remember. For a 4 x 5 image scanned
at 100 dpi: (4 x 100 dpi) x (5 x 100 dpi) = 200, 000 pixels
To calculate the file size multiple your pixels by 3. 3 represents
RGB values: 200,000 x 3 (RGB) = 600 kb
There are reasons to do higher scans. You might want a particular
image/graphic to be downloadable and printed off a color printer.
A 72 dpi print is invariably of poor quality. My advice is to
do two separate scans. One low resolution scan and one high one.
Use the 72 or 100 dpi image on the web page but have a link to
the higher quality image if someone wishes to download it for
printing.
Problems Scanning Halftone Images
Halftones are images from magazines and newspapers. Unlike photographs or clip
art images from newspapers and magazines are created from dot patterns. If
you look closely, or use a magnifying glass, you can see the images are made
up of thousands of dots. When you scan a halftone you often get what is called
a 'moiré pattern,' a distracting pattern of lines. The best way to avoid
this distortion is to use a 'descreen option' that counters the 'moiré pattern.'
Fortunately my scanner software comes with this option. In fact a 'descreen
option' is one of the most important capabilities you will want in your scanning
software. If your software lacks this feature you can still minimize the
effect using filters found in programs like Paint Shop Pro or Photoshop.
This usually involved blurring the image to some extent.
Paint Shop Pro 7.0
I visited the JASC site to gather these scanning tips to reduce the moiré effect:
1) Rotate the image 30 degrees and rescan. 2) Scan at a higher resolution (say
266 dpi) and resample down to (100 dpi). 3) Go Image - Normal Filters - Soften
- to blur the pattern 4) Go Image - Special Filters - Median
Photoshop 5.5
I checked a number sources to gather these scanning tips: 1) Scan the image
at the actual print resolution. For example most magazines are printed at
133 lpi (lines per inch) the correct resolution for your scanner would be
266 DPI. Then resample the image down to 72 DPI. 2) Use an 'Unsharp mask.'
Go - Filter - Sharpen - Unsharp Mask. Try different settings. 3) Use the
'Despeckle' function on the entire image or only a single channel. Go - Filter
- Noise - Despeckle 4) Use the Median filter. Go - Filter - Noise - Median.
5) Use a combination of these methods.
Final Scanning Tips
Close other applications when scanning. Buy more Ram memory. When you double
your scanning resolution the memory cost goes up four times. Don't scan black & white
or grayscale art at 24 bit resolution. Scan using lineart or grayscale settings.
Keep the glass clean. Wipe gently using Windex on a soft cloth. Never spray
any cleanser directly on the glass.
