V1.02
Thom Hogan’s Complete Guide to the Nikon D300
Page 745
might report your JPEG images as having 72 dpi. Are you
confused yet?
Don’t be. Most of the numbers you encounter in the
resolution world are arbitrary. Let’s make them work for us.
Your camera can capture 4288 pieces of information across
the (usually) horizontal axis. That’s an
absolute
. There really
are 4288 pieces of data to deal with in that axis. What
happens as that image moves to other devices is where things
get murky for some.
On your computer monitor, for example, you might specify to
view your 4288 x 2848 pixel image via your software’s
Fit in
Window
command. If the maximum size of that window is
640 x 480, obviously the software has to
scale
the original
data in some way. Normally, it does this by creating a
temporary, interpolated
copy
of your data. Nothing changed
in your original data. But you’re also no longer looking at
your original data! That’s why you’ll find that most tutorials
on post processing ask you to look at the effects of destructive
tools like
Sharpening
filters at
100% View
. That way you
see the exact effect on (a portion of) your original data, not a
simulation of it.
Bottom line:
viewing at different scales or
sizes on your computer monitor does not change the actual
“resolution” of your image.
Another place where we see resolution numbers is in the
software we use. For example, if you use Photoshop CS3 or
Photoshop Elements
Image Size
command, you’ll see a entry
called
Resolution
that’s specified in
pixels/inch
(or
pixels/cm
). For D300 JPEG images this value will normally
be
72
. This is an
arbitrary
assignment by the software program
and sometimes controlled by a value in the EXIF data. Above
this value you’ll see values for the width and height for the
image if it is printed at that dpi. Read it this way:
IF you print
at that pixels/inch value your photo will be X” high and Y”
wide.
That’s a big IF. Usually we want to print at a specific
pixels/inch value that will maximize the output of our printer.
