242 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY
- Keep file size in mind while you work. If you
are pasting a large number of images, you
might need to “merge down” some layers to
keep the computer/RAM happy. The only
indication that things are out of control
(RAM-wise) is that Photoshop will slow to a
crawl. Use the Layer, Merge Down command
to keep layers organized. - Adjust the tones and colors of each individ-
ual layer using adjustment layers. If your
composition works, you will create an artifi-
cial but interesting group portrait, or a com-
plete joke!
This general exercise is just a guide to help you
consider the issues common to photographers and
artists who merge images together.Preventing Color Banding and
Data Loss in Adjustment Layers
Normally, as you edit an image, its data is altered forever. For example, if you
change gray pixels into pure white pixels, the changed pixels are given new values
of red 255, green 255, and blue 255. If you cannot Undo the change, all records of
the original values are lost forever. Often, after a series of edits, the original data is
so altered that only a few thousand of the original 16 million colors remain. The
result is that banding is visible (see Figure 16.6).
The image on the right in Figure 16.6 has gaps that look like the teeth of a comb.
These gaps represent brightness levels where data was lost during editing. At the left
is the histogram box for an image that has had the same editing done with adjust-
ment layers. The image has smooth gradations, and all of its original tones are pres-
ent in the histogram.
Without adjustment layers, colors can show bands. A histogram can be used to diag-
nose banding. This image was previously edited with Curves, Color Balance, Hue,
and Saturation commands. Banding is visible; the tonal gradation has an abrupt
staircase appearance instead of a smooth, normal transition.If you paste in an
image and it is dramati-
cally larger or smaller than the
other images, the file resolution
might need to be changed. Delete
the new layer or choose Edit,
Undo and then return to the
image and change its resolution
by choosing Image, Image Size
(Photoshop) or Image, Resize,
Image Size (Elements).