But layers come at a price. Because they are actually independent
images, each layer consumes space both in memory and on your
hard drive. So as you add layers, your composition gets bigger, and
Photoshop requires more space in memory and on disk to manage
the file. Generally speaking, you can let Photoshop worry about
these sorts of nitty-gritty details. But bear in mind, no matter how
sophisticated your computer, its memory and hard disk are finite.
And if either the memory or (worse) the hard disk fills up, your
ability to edit your marvelous multilayer creations may come to a
skidding halt. Fortunately, a few precautions are all it takes to keep
layered compositions on a diet and Photoshop running in top form:
- First, don’t let your hard disk get anywhere close to full. I rec-
ommend keeping at least 25GB available at all times, and more
than that is always welcome. (Consult your computer’s docu-
mentation to find out how to check the space available—or just
hope and pray you’re okay, like everyone else does.) - Back up your Photoshop projects regularly to DVD, an external
drive, or another storage medium. Doing so not only preserves
and protects your images but also permits you to delete files
from your hard disk if you start running out of room. - As you work in Photoshop, you can keep an eye on the size
of your image in memory by observing the Doc values at the
lower-left corner of the image window (see Figure 5-2) or in the
Info panel. The value before the slash is the size of the image if
flattened; the value after the slash tells you the size of the lay-
ered composition. - You can reduce the size of an image by merging two layers into
one using Layer→Merge Down, which we’ll put to use in this
lesson. - To merge all layers and return to a flat image, choose
Layer→Flatten Image. But beware, this is a radical step. I usu-
ally flatten an image only as a preamble to importing it for
another context like a book or my Web site. And even then, I
make sure to save the flattened image under a different name
to maintain my original layered file.
Finally, when in doubt, err on the side of too many layers. This may
sound like strange advice, but it’s better to push the limits and oc-
casionally top out than unnecessarily constrain yourself and hobble
your file. You can always upgrade your technology to better ac-
commodate your massive compositions, but you can never recover
an unsaved layer (one that you merged or flattened before saving).
Figure 5-2.The Benefits and Penalties of Layers 131