Digital Prints

image in Chapter 8. However, this is a good point to review one part of the image-editing
workflow that always confuses people and that I introduced in the scanning section earlier.
I’m talking about scaling or resampling to change a print’s size.
As we learned earlier, scaling means stretching or compressing an image’s pixels to fit a certain
size on the paper. This is also called resizing. Resampling, on the other hand, accomplishes
the same thing but in a different way.
Let’s see how this works with a hypothetical, bitmapped photo image. (Although I’m using
Photoshop CS here, you should be able to take similar actions with other image editors
with only slight modifications).
In Photoshop’s Image Size dialogue box (Image > Image Size), you are confronted with an
array of settings and options (see Figure 3.19).
The top portion is titled Pixel Dimensions, and it
merely measures the number of pixels across (Width)
and the number down (Height). The number of
pixels determines the amount of information or
detail contained in the image; more is better.
The next section down is titled Document Size,
and this is where the critical decisions about image
size and resolution are made. The key to how this
section works is the little check box at the bottom
called Resample Image. By either checking or unchecking that box, you are committing
yourself to either scaling (resizing) or resampling, and as we already know, they are very different
things. Let me explain the impact of this important choice.
With the Resample box unchecked, there is now a direct correlation among height,
width, and resolution. If you change one, the others change, too. But, in this case—and
this is the important point—you are not changing any pixel data! You can prove this to
yourself by changing the Resolution number while keeping an eye on the Pixel
Dimensions; they won’t budge (see Figure 3.20). In essence, what you are doing is taking
the same number of pixels and spreading them over a larger or smaller amount of
space. You are only scaling or resizing the image, and since you’re not actually printing
pixels but dots, the printer driver’s (or RIP’s) dithering or screening method will try to
cover up the differences, usually successfully.
Following this latter method
with my hypothetical image, if
I have Resample Image
unchecked and change the
Resolution from 300 ppi to,
say, 200 ppi, the Document
Size has now magically changed
from 8×5.4 inches to 12×8.1
inches. In other words, the
image is now larger in size
because I lowered the image’s
Chapter 3 ■ Creating and Processing the Image 107
Figure 3.19 Photoshop’s important
Image Size screen.
Figure 3.20 With Resample Image
unchecked, decreasing the resolution
from 300 ppi to 200 ppi increases the
print size without affecting the pixel
information.