Individually, these terms might make sense (on an alert day), but when these terms
and their associated technologies are used together to edit or output a digital image,
only experienced graphic artists and photographers really understand what is going on.
Here is an example:
Sarah, an ambitious beginning photographer, is asked to photograph her best friend
Cynthia’s graduation party. She arrives at the party with her 4-megapixel digital
camera and fills up her memory card with dozens of images. At home, Sarah copies
the images to her computer. Cynthia calls and asks Sarah to put the best images on
Sarah’s Web site for review. Sarah picks the 10 best images and begins to upload.
Even with her fast DSL connection, the upload takes 20 minutes, far longer than
Sarah expected. Cynthia gets online, sees the images, calls, and says the images are
so big she can’t really see them on her screen. So, Cynthia asks Sarah to simply print
out the images and bring them to her house. Frustrated, Sarah opens each image in
Photoshop, reduces its size, and then uses the File, Print Command.
The images print out, but are pixelated and a mess. She takes them to Cynthia, who
promptly decides none of them were good enough to keep. Distraught, Sarah throws
up her arms, runs out the door, and munches on cupcakes for the rest of the week.
The images were fine, but Sarah used the wrong resolution twice: online and in
print. She took perfectly acceptable photos, but her presentation failed because she
didn’t understand when to use the appropriate resolution.Understanding Different Terms for Resolution
The term resolutionis formally defined as follows: The process or capability of mak-
ing distinguishable the individual parts of an object, closely adjacent optical images,
or sources of light.
In simpler terms, resolution is a measure of elements or pixels in an image. The
number of pixels in a digital image or dots in an inkjet printout, for example.
Cameras currently use the term megapixelto define their resolution; printers use dpi,
and scanners use ppi. Let’s sort out the terms used by digital photographers that refer
to resolution.
Photographers and printers use the following terms when discussing resolution:
■ ppi. Pixels per inchmeasures how many pixels that are lined up side by side
that fit within a one-inch square. A computer screen varies between 72 ppi
and 96 ppi. Scanners will scan anywhere from 300 ppi to 2400 ppi or more.
In other words, the number of pixels it creates within an inch as it scans an
image.174 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY