Welcome to this Tutorial page of
Your Creative Source
Assembling multiple scans of one image.
Part one: The Scanning Process.
It is often the case that when scanning images
we need to make two or more scans and assemble them
into one coherent image for printing or publishing on the web. There
are some simple methods to make the
assembly process easier...
First, look at the image in relationship to the
scanner bed size. How many scans will it take to complete the
image? If you're lucky, it's only two, but if you don't have a digital
camera that's up to the task it can be intimidating to try scanning
something as large as a poster. For example, the Space Jam
poster below was assembled with more than twenty
scans. It took a long time, but the result was a quality
image. (Click the thumbnail below to see the result.)
We wouldn't recommend you start out with assembling something
so involved, but you can apply what's here to any number of scans.
Once you've figured how many scans you'll need to make, you
need to think about the area of the overall image that's most
important to get right. Choose that area for your first pass,
and take as much time as you need within your scanning
software to make all of your color and tonal adjustments
as near as you can to the original. (For some rules of thumb
about image prep, see Tutorial 2b.) Don't worry now about
making adjustments you may have in mind to improve
the image - that is best done after you've finished assembly.
Now note your settings: This is important! You
are going to scan every successive pass using the same settings
no matter how the preview looks. Use that first scan as an anchor for
the remaining passes. Otherwise, you'll have to
adjust every scan to every other scan manually - a nightmare!
The only setting change you can safely make is rotation.
Another thing to mention here is that you may need
to remove the cover of your scanner to access the center area
of larger images - if you have a lid that must be removed using
tools you're on your own. We can't make that judgmentfor you,
but if you decide to go ahead the risks are yours.
Clean your scanner glass and dust the art thoroughly.
General tips to make your scans easier to assemble:
Show an edge wherever possible to aid in alignment.
Get each scan as "level and plumb" as you can.
Overlap each scan as much as possible without adding to the total;
if you can't get an overlap of more than a bit, add a pass.
Keep the work absolutely FLAT on the scan bed; if you must
mount the image on board to do this, it's worth the effort.
Use a logical method to scan and name each pass, as if you're
reading a book, from top left to bottom right the names
should be in order. Think "rows and columns." This
is really important if you're assembling more than four scans.
(By the way, as long as your settings are based on the
anchor area, you do not need to start with that area.)
Save all scans in one folder as they're made.
(We're going to use a simple two scan assembly for this
tutorial, but the process will work on any number of scans as
long as you and your computer can handle the complications
and precision needed to work with that many layers.)
Here are the two scans we'll be working with,
courtesy of Terry Jasinski:
Preparing for assembly.
First, open each scan file one at a time and perform
a rotation to correct any "out of plumb" scans. It seldom
happens, as shown in the shot below, that the scan angle is
exactly on zero degrees. Don't let it worry you if it's off a
little - it's easy to correct in Photoshop.
Choose one of the long border lines (a long straight edge anywhere will
work when it's all you have, but it's a bit more complicated). The edge
you choose should be seen across as much of the overall image as possible.
First, zoom in to a size where you can see the chosen line clearly on screen.
Choose the measure tool...
...and click on the chosen line (the top or bottom, but precisely on the line);
drag all the way to the other end of the line;
center your cursor in the same precise position relative to the line
as the first click, and release. If you look at the top right of
the ruler options palette, you'll see that an angle has been measured.
Now, depending on whether you're working with a border edge
or an "interior" line, you'll do one of two things:
If it's a border edge, simple go to Image>Rotate Canvas>Arbitrary
and you'll see a dialog box with the necessary correction already entered
for you in the window... how easy can it be? Just click OK, and your scan is
now "plumb and level."
Here's what a rotated image looks like:
If you're working with an interior line, it gets a little more
complicated in that you'll need to either:
Let the auto correction work and assemble
your layers at a consistent offset angle
- or -
Do the math to adjust all images to "plumb."
What' our recommendation? Use the auto correct when possible;
it's complicated enough when you're working with many layers.
Just remember that you are attempting to rotate ALL scans
to the SAME angle, so take some time to plan ahead.
You can, and probably will, need to rotate a layer individually
later on, but get them as accurate as possible now.
Perform this operation on every individual scan and save your work.
On to Part two: The Assembly Process
Click here for a printer friendly version of the complete tutorial.
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