What is a "cel," anyway? Basically, it's short for "celluloid": a sheet of clear
acetate or nitrate that is hand-painted and photographed over a background.
The outline of the character is inked or copied to the front of
the cel. The colors are hand-painted on the back.
There are many different kinds of cels; below are some definitions that may help
you keep things straight.
Those that actually go under the camera are called
production cels (these are the most valuable).
Production cels and backgrounds are peg-punched so they can be aligned when photographed.
Along with the cels, of course, are
backgrounds. A background used in the production is called a
master background, and because they used the same background through
several successive cels, these are much less common. The rarest find is
a production cel WITH its matching master background.
Non-production cels include
model cels, which are for reference. Also the term
color test cel is sometimes used. These cels are produced to see
how the color mix actually looks on acetate, etc. (Note: some definitions include
model and color test cels in the production category, even though they never actually
appear under camera. If this is important to you, please be sure to ask whether
the cel appeared under camera or not.) Before such a cel is painted, it is standard
practice to create a drawing first - this shows the outline of the character, and
notes on the areas to be colored.
are hand-painted cels made as gifts.
There are also limited
edition cels, non-production hand-painted cels created specifically for
collectors (although some collectors disdain them as being "artificial"). Produced
in limited quantities, they are most easily identified by a fraction (ex: 37/500)
in the lower right-hand corner which indicates both the total number of items created
(the larger number on the right) as well as the particular number assigned to the
object being viewed. They were not used in a film, and have merely been created
to resemble original production art, whether by reproducing a scene, or more recently,
creating new scenes which often mix characters who do not traditionally belong together.
Finally, there are sericels,
a non-production silk-screened cel similar to a limited edition, but no work is
done by hand. Often produced in editions of 5,000 - no hand-painting involved. Made
for the low-end resale market.
Some of the above definitions were found on a page at the "Wonderful World of Animation
Art Gallery"; follow the link to see the page, which contains more information: