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.

Publicity cels 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: Animation Art Definitions