Graphics Programs Reference
In-Depth Information
you see banding, this is the result of the 8-bit video subsystem and the
Color Look-up Table. A Photoshop gradient should appear perfectly
smooth since there is no banding in the document. Rarely will you see
this unless once again, you're using a great display system like the Barco
Artisan or Eizo using a 10-bit LUT. This can be an issue since it's useful
to know that when you do see banding, you know whether it's in the
file or not. If you see banding on an Artisan, you can be assured that the
banding is in the file itself, and not an artifact of the display system. Also
view the gradient to see if it appears neutral from black to white. It is not
uncommon to see color shifts from neutral to slightly green and then
slightly magenta as you might have seen in the test using the black doc-
ument and curves above. Ideally, this gradient will look neutral from end
to end.
Tutorial #11: Using Photoshop to Build Simplified
Camera Profiles
It is common to find a situation where conventional digital camera pro-
filing tools don't work well or are too expensive for some users. Some
digital cameras provide only 8-bits per color; sometimes it is questionable
to take such files and convert from an input space to a working space
just to begin the editing process in Photoshop. Many of the consumer
and Prosumer digital cameras produce RGB data that is reasonably close
to some of the better known RGB working spaces in Photoshop, usually
sRGB or Adobe RGB (1998). The following tutorial can be useful to those
users that have cameras whose data is somewhat close to a standardized
RGB working space. It can work for users who simply do not have the
budget to buy special targets and camera profiling software or for those
that are not happy with the results using profiling packages. It should be
pointed out that this technique is no substitute for high quality custom
camera profiles.
Important
: For this technique to work properly, you must have a
calibrated and profiled display. A 24-patch Macbeth color checker target
is highly recommended as a subject for creating these profiles. Although
we will not use the target as a reference within a true profile-generating
application, this target provides an excellent visual reference in which to
produce our profile since all the work will be done visually. We will
attempt to visually match the color appearance of this standard target to
what we see on screen from this photographed target. If possible, have
the Color Checker in a D50 light box (preferably with dimmer) near your
calibrated display so you can reference the screen and actual Color
Checker.
1.
Process the data from the digital camera so it can be opened in
Photoshop. If there are various options for doing this, you may
have to try different techniques but once you have the data,
always use these settings in the camera software.
