ACE Coin Scanning Tips
by Mike Dalka
Many people have easy access
to a scanner... and while it does take a bit of work, you can produce a
good-quality scan of your coin using most any scanner. There are a few mistakes or stumbling blocks
that are usually the downfall of scanner-produced images, and the steps below
attempt to circumvent those problems.
You don't have to use this technique if you have one of your own, but
this is a guide for those with little or no experience scanning 3D objects on a
scanner basically intended for 2D documents.
1. Create more image
depth by placing the coin on an incline.
Even though everything between the coin and the scanner "eye" adds a
potential source of distortion, using a piece of glass (such as from a small
picture frame) to elevate one end of the coin more than the other is
recommended. A common complaint with
scanner-made images is loss of detail.
Placing the coin on an incline will help add the effect of more natural
lighting, and create more recognizable detail.
I use a 4 x 5 piece of glass, placed on the scanner bed, and elevated on
one end by a ballpoint pen underneath.
Try placing the coin so that the top of the subject is on the high point, then try it 180 rotated. Different scanners place the "eye" in
different places, and by experimenting like this, you can see what creates the
most natural and visually appealing contours.
Of course, you can always use software to reorient the image if it is
upside down, but elevating the opposite side of the glass is easier.
2. Don't exceed the
OPTICAL scan resolution of the scanner.
Many scanners use a
technique called "Software interpolation" to produce images with an effective
resolution (image quality) that is better than the hardware inside the scanner
can actually produce. It does this by
adding "blank spaces" between every line of pixels that make up the image. The software then analyzes the pixels in
front of and behind the "blank" lines it created, and filling those blanks with
the average color of the pixels around them.
This useful technique is great for making scans of things with
relatively smooth color gradients, but it produces extremely undesirable effect
when scanning rough surfaces like those on an average coin. Most scanners today can produce scans of 300
DPI without using software interpolation.
Try scanning at 300 DPI if you are unsure of the scanner's optical
resolution; if the detail seems "soft" or blurry, you may want to step the
resolution back a notch or two and try again.
Believe it or not, for scanning coins, sometimes a lower DPI will
produce a more visually pleasing image!
4. Pay attention to the
background against which you scan.
I like to leave the lid up
on my scanner when scanning most coins.
This will produce a darker black background than anything you could
place over the scanner, so long as there isn't too much light in the room
(normal ambient light is usually ok, but any fluorescent light above the scanner
should be turned off). Some coins appear
more pleasing when scanned against a white background, and for these situations
simply laying a sheet of white paper over the coin will work well. If you have a high-quality laser or inkjet
paper available, these sheets work really well, because they are extra-bright
and extra-smooth, but don't rush out to buy some if you don't have it on hand.
5. Don't scan too much
Once you prescan the coin,
most scanners allow you to easily crop the scan area. Please make the scan area as small as
possible without getting overboard about it!
Leave just a small border of blank space around the coin when you scan
it. This will keep the image size as
small as possible and make the images upload and download faster.
6. Save the image as a JPEG
(.jpg) or GIF (.gif)
Once you have the perfect
scan, save it in the perfect format!
JPEG is a lossy (meaning it sacrifices some image quality to compress
the file size) file format designed specifically for compressing photographic
images. The GIF format is not as
effective when used for photographic type images, but it works well too. Both of these formats are widely supported. One word of caution though - it is possible
to over-compress an image in the JPEG format and ruin all your hard work. Overcompressed JPEGs lose so much detail that
small features completely disappear. To
further complicate things, there is no standard way of expressing how much
compression is being applied. For
instance, Adobe Photoshop expresses JPEG compression as a percentage of the
original (uncompressed) image quality.
As an example, in Photoshop a JPEG saved at an image quality of "70" is
better (and bigger) than an image saved at "60" quality. Conversely, Jasc Paintshop Pro expresses JPEG
compression as a percentage of maximum compression... so an image saved at "70"
compression is extremely compressed, and is the same as an image saved at "30"
in Adobe Photoshop.
Confused yet? Well, the good news is, 50% works well in
most cases. If the image you saved at
50% is a bit more blurry than you would like, then try it again, saving the
image at 60 this time... if it looks worse than the first, try 40 instead.
Ideally, the images you
produce will be less than 100K after compression (saving them as JPEG or GIF
images). If you want to play around with
the compression factor to get the best possible image to size ratio, by all
means, be our guest! If you are less
technically inclined and want to skip it, just set the compression to 50 and go
This should get you started
off on the right foot when producing the images to send to ACE for
judging. Many people have access to a
digital camera, and if you do too, you might want to try both the scanner
technique described here and the camera technique described in the accompanying
document Mark Lehman has produced.
Either way, the tips ACE has assembled will help you produce the best
image that can be produced from whatever hardware is available to you!
Good Luck and Good