Understanding Photographic Plate Sizes
inAugust 30, 2012 - 7:43am
Every category of collecting has its own special terminology and photography is no exception. One of the terms that often confuse those who don’t specialize in early photography—like a general line dealer or casual collector—is plate size.
Almost all auction catalogs and sales advertisements of 19th century photographs are listed described in plate sizes such as “full plate”, “quarter plate” and so forth. But virtually never in the typical specialist’s description will you find a conversion of plate size to inches. While referring to images only as fractions of “full plates” may be easily understood by photographic specialists, many prospective buyers have no idea of how large a full plate is let alone the sizes of smaller plates.
And why should they? If you collect Colt revolvers or teddy bears or laminated rosewood furniture and just want a vintage image depicting what YOU collect, why should you have to learn a specialized language? But the folks who write the descriptions don’t take this into consideration and continue to write descriptions in their own obscure language.
So here is the secret code of plate sizes. A full plate is 6½ inches by 8½ inches (55¼ sq inches). All other sizes are simply smaller units of that surface area as shown in Table 1. A quarter plate, for example, is 3¼ X 4¼ or 13.8 sq. inches (full plate of 55¼ sq. inches divided by 4 = 13.8). Although not every plate exactly follows that formula, it was close enough to establish the custom of using “plates” rather than inches when referring to image sizes.
Photographic plates were used from about 1840 to the late 1880s. Plates were made of sheets of various metals coated with light sensitive chemicals. Photographic plates were temporarily held in wooden frames (Fig. 2) for loading into cameras. Early 19th century cameras were little more than wooden boxes with a lens. The plates were exposed by simply removing the lens cap. Each plate produced only a single image.
The daguerreotype, developed by Louis Daguerre around 1840, was the first practical photographic process. A daguerreotype plate was a sheet of copper coated with a polished silver coating. Around 1852, plates began to be made of glass coated with a chemical compound and are known as ambrotypes. In the mid 1850s, glass plates were replaced by small thin iron sheets which also used a modified chemical coating. Although these sheets never contained any tin, for some unknown reason they became popularly known as “tintypes” which is the name still used today (except of course, among photographic specialists who use the words ferrotype or melainotype when referring to tintypes).
Daguerreotypes, ambrotypes and tintypes are all one-of-a-kind unique images. In each case, the plate exposed in the camera was also the finished product. If a photographer wanted 10 final images of President Lincoln, for example, 10 separate plates would need to be loaded and exposed. Around 1890, film began to replace the rigid metal and glass plates. By shining light through a film negative onto light sensitive paper, many photographic images could be made from the single camera exposure which produced the negative.
Plate Sizes - Table 1 Full 6½" X 8½" Half 4¼" X 5½" Quarter 3¼" X 4¼" Sixth 2½" X 3" Ninth 2" X 2½" Sixteenth 1 3/8" X 1 5/8"
The relative sizes of three common plate sizes are illustrated with this image of Honest Abe. The smaller plates, middle and right, are fractions of the total square inches of a full plate, left.
plateholder.jpg A typical wood photographic plate holder used in a 19th century camera. This particular example is marked “E & HT Anthony & Co” which was one of many manufacturers of plate holders.
Written by Mark Chervenka