The Textbook of Digital Photography - PhotoCourse

ChApter 1. digitAl CAmerAs & imAges

34 For more on textbooks in digitAl photogrAphy, visit http://www.photoCourse.Com

http://www.photocourse.com/itext/biglie/

interPolAted reSolution

Beware of claims about resolution for cameras because there are two kinds of

resolution; optical and interpolated. The optical resolution of a camera is an

absolute number because an image sensor’s pixels or photosites are physical

devices that can be counted. However, optical resolution can be increased

using a process called interpolated resolution that adds pixels to the image

to increase the image’s size. To do so, software evaluates those pixels sur-

rounding each new pixel to determine what its color should be. For example,

if all of the pixels around a newly inserted pixel are red, the new pixel will be

red. What’s important to keep in mind is that interpolated resolution doesn’t

add any new information to the image—it just adds pixels and makes the file

larger. This same thing can be done in a photo-editing program such as Pho-

toshop by resizing the image. Beware of companies that promote or empha-

size their device’s interpolated (or enhanced) resolution. You’re getting less

than you think you are. Always check for the device’s optical resolution. If

this isn’t provided, you’re dealing with marketing people who don’t have your

best interests at heart.

one term—two meAningS

The term “resolution” has two meanings in photography. Originally it re-

ferred to the ability of a camera system to resolve pairs of fine lines such as

those on a test chart. In this usage it’s an indicator of sharpness, not image

size. With the introduction of digital cameras the term began being used to

indicate the number of pixels a camera could capture. Two meanings for the

same term is not a good turn of events in any field.

Test charts have pairs
of lines at various
spacings

If an image is too
large for a screen
(top), the viewer has
to scroll around it.
When sized correctly
(bottom) they can see
the entire image. Most
digital photography
programs automatically
resize images to fit the
available space unless
you specify a different
size.

http://www.photocourse.com/itext/resolution/

Click to explore the

resolution—The Original meaning

“resolution.”

Click to see how some
cameras inflate their
pixel counts.