Chances are you've seen a
representative sample of stamp scans - perhaps on eBay auctions, and
you'll know that they range from good to disgraceful.
Making good scans of your
stamps is simple.
What resolution to scan at
In choosing the resolution
to scan at you usually need to compromise between image detail and image
size, especially if publishing a scan onto the internet where you don't
want to cause people connected via slow modem lines to suffer a very long
If you are scanning so that
the scan will be used in a professionally printed magazine or book, you
will normally scan at 300 dpi for the stamp to be shown 'full size' (or
actual size) in the printed book.
If you want to enlarge the
image, then the best way to do this is to scan at a higher resolution
rather than to subsequently expand the scanned image - for example, a 600
dpi scan would be (obviously?) twice as big when printed out as a 300 dpi
Although I just said that
the picture would be twice as big, in actual fact, it is twice as big in
both the horizontal and vertical dimensions, meaning that, in total area,
it is four times as large, and so the file size also will be approximately
four times larger.
If you want to scan an
image to display on a typical computer screen, then because most monitors
typically have a dot pitch in the other of about 70-75 dots per inch,
you'll find that a scan in this type of setting will give you a close to
'real' size image. But it isn't going to have as much detail, of
course, and so when scanning stamps to display on the screen, I
recommend that you use a setting of 150 dpi or more so as to show a
reasonable amount of detail.
There is one other issue to
consider when choosing what size to scan your images. If the images
are intended to be displayed on a typical computer monitor, you probably
want them able to completely fit on the screen rather than only partially
appear and require scrolling. These days it is fair to assume that
everyone has a screen with at least a resolution of 800x600. You
might think, therefore, that as long as your images are no bigger than 799
pixels wide and 599 pixels high, they can easily be seen on the screen,
but remember that if the image is being viewed in a web browsing window,
then the web browser program takes up screen space at the top for its menu
bar, on the sides, and at the bottom, and so maybe you should consider
perhaps 700x550 as the maximum size that can easily be viewed (through a
web browser) on the screen at one time for most people. At 150 dpi,
this would be an image with an original size no greater than 4.6"x3.5",
and at 300 dpi, this would be 2.3"x1.8" - not very big, but larger than
just about all normal stamps.
Click on this link for
examples of scans at
different resolutions. It will open in a separate window and
probably takes quite a while to load.
Pre-scan Exposure settings
The most important time to
make adjustments to how your image appears is before you scan it.
Any changes to scanning settings is reflected in the original scan, but
after that, any time you make changes in an image editing program, you
lose some quality at the same time (sort of like what happens when you
make a photocopy of a photocopy, or a copy of a videotape).
The most important setting,
after resolution is something that might be called "Levels" or
"Brightness" or "Exposure" or something like that in your scanning
program. If you have a good scanning program, you typically take a
preliminary scan of probably the whole scanner, then you select the parts
of the image that you want to actually make a copy of, and then you can
make adjustments to the scanner settings before actually doing the scan.
Click on this link for
illustrations of different exposure settings and a discussion on how
to adjust for best results (it also will open in a new window).
There is one other
important setting that your scanning software probably allows you to
specify - the ability to 'sharpen' the scan. While you don't want to
alter the image you're scanning, a mild degree of sharpening helps to
counter the blurring that inevitably happens with the mechanical scanning
process. Click on this link for
samples of different levels of
What File Format to Save the Scan
Sooner or later, you're
going to have to tell either the scanning or image editing program what
type of file you want to save the scan as. You'll probably have
several different choices, including some or all of these :
GIF - The good news
is that this is a common type of image file type which all web browsers
can display. The bad news is that it only supports 256 colors (your
image probably scanned at 24 bit or 16.7 million colors) and it doesn't
compress very well. Never use a GIF format for stamp scans.
JPG - The good news
is that this, too, is a common type of image file type which all web
browsers can display. More good news - it can also display all 16.7
million colors that you scanned, and does compress well. The bad
news? Yes, I'm afraid there is some! :) When it
compresses a file it does this by ignoring some of the finer detail and
simplifying some of the other detail - it is what is called a 'lossy'
compression method and so each time you open and save the file, you're
potentially losing more and more data.
PCX - A largely
obsolete file format these days. Don't use.
TIF - Most browsers
can't display TIF files. Furthermore, TIF files have very little
compression, meaning that they can be enormous in size - maybe a hundred
or more times larger than a comparable JPG file. However, the good
news is that data is stored in a lossless manner - you can open and save
TIF files as often as you like and not lose any of the detail.
Accordingly, if you're
going to be doing any further work on an image (such as editing it,
cropping it, or whatever) then you should save your working and 'master'
copies as TIF files. If you're preparing images for print
publication, you should probably submit them as uncompressed TIF files.
However, when you're ready to publish the image onto a web site, at that
stage you should convert it from its TIF format to a JPG format.
The big issue when saving
an image as a jpg type file is how much compression to use.
Different graphics programs offer different sets of compression options -
for example, my Photoshop has thirteen different settings (0-12), others
might have more or less.
In choosing a compression
setting, you are making a trade-off between image size and image quality.
The smaller the size, the poorer the quality. Where is an
appropriate compromise point?
Click here to look at
examples of an image with
different compression settings. We are suggesting that the best
compromise between file size and image quality is where you compress the
file by about 25%-40%; in other words, favoring image quality slightly
more than file size.
Post scan settings
If you've set up the
parameters for your scan correctly, there shouldn't need to be much that
you need to do to the image after scanning it.
One thing to pay attention
to is cropping the image. If you're publishing the image on the
internet, you want to crop as closely to the image of the stamp itself as
possible - all the extra unnecessary border or frame that you also scanned
is merely adding to the file size and slowing the download time without
adding any interesting extra picture detail.
If you're not happy with
the image after scanning it, the best thing to do is simply to re-scan it.
However, if that isn't an option, then you might want to edit the image,
for example to sharpen it, crop it, adjust the brightness/contrast levels,
and perhaps to create thumbnails of the images in addition to the
a step by step worked example of
correcting a bad scan.