Digital Prints

80
Mastering Digital Printing
■ But I’m scanning for printing. What about printers? Printers are very different from monitors
or computer screens. Scan resolution does NOT determine image size on the printer
as it does with monitors. The size of the original scan area in combination with Scaling
(see below) determines printed image size. Lower resolutions may look fuzzy, and higher
resolutions may look better, but the printed size on paper will be the same at any scan resolution.
The size is changed by the Scale or Magnification setting of the scanner.
■ What is Scaling? What is Resampling? What’s the difference? Scaling is a word that means
stretching or compressing the image pixels to fit a specified area of paper, and it is very
different from changing the size by resampling. Scaling is accomplished by simply changing
the value of the number used as resolution when the printer calculates the spacing of
the pixels on the paper (ppi, pixels per inch). Scaling only changes the future pixel spacing
on paper so the image prints at a different size. Scaling is a simple operation, but the
concept is a little abstract.
There are two ways to scale an image: (1) after the scan and (2) during the scan. Scaling
after the scan is discussed in “Sizing with Image Editing” later in this chapter, so we’ll concentrate
on scanner scaling here.
The scanner’s scaling control is simply a calculator to help with the arithmetic. The settings
for a sample 4x4-inch reflective color print scanning at 300 dpi are shown in Figure
3.3. If the scaling factor is 100%, then the scanning resolution (or Source or Input) is
100% of the printing resolution (or Target or Output). The 100% means that the image
is scaled to print at the same original size at the specified printing resolution. (If you switch
to scan 35mm film at 4000 dpi at 100%, and you print it just like that, it will indeed
print at original film size at 4000 ppi or at the same small size of a 35mm film frame:
.94 × 1.42 inches.)
If you change the scale factor to say 50% and keep the same 300 dpi, then the scanner
will scan at 50% of the 300 dpi value, or at 150 dpi scanning resolution, to create the
right number of pixels to print half size—or 2x2 inches—at 300 ppi (see Figure 3.3 again).
The image will be scaled to print at the specified 300 ppi that you asked for. So, if you
Figure 3.3 Left: Sample scan showing
a scaling factor of 100%. Note how
Source and Target dimensions are
equal. Right: When the scaling factor is
changed to 50%, the target print size is
cut in half.