Most people think a fashion print is one of those hand-colored lithographs from Godey's Lady's Book or Peterson's Magazine. So many of the illustrations from these periodicals of pre- and post-Civil War days ended up in frames on the bedroom wall. They have been prized for their charm as period graphics; they also are informative social records.
Yet despite the decorative and historic interest, a Godey or a Peterson has only a mediocre rating on the current print market. Neither makes the heart of a serious collector beat faster. The connoisseur who measures them against the rest of the fashion plate outlay - which is considerable - is not giving the foldout pages from these 19th-century magazines his blue-chip rating. What he seeks instead is the Rembrandt or the Matisse of fashion prints. He will thus pass up the delightful $15 Godey and will readily write out a check for $150 (or more) if he succeeds in finding a rare 18th-century aquatint bearing the mark of Niklaus von Heideloff. He might pay almost as much for a brilliant 20th-century illustration colored by the pochoir process if it is signed by Georges Barbier.
Like any other specialized hobby, fashion-print collecting has its arcane aspects. It has an avid following that includes almost anyone who is fascinated by the changes of style and taste in clothing; it includes students of the decorative arts and members of the fashion world who have scholarly inclinations. Considering the number of excellent plates still extant (thousands were turned out in England and France during the peak period of production that spanned the whole of the last century and extended well into the present one), the field is wide open for more collectors in the future.
An exceptionally comprehensive exhibition (''Fashion Prints: 125 Years of Style'') of more than 200 plates is on display at the Cooper-Hewitt Museum, the Smithsonian Institution's National Museum of Design, in New York (through Jan. 2 , 1983). The show surveys the era when the fashionable woman gave more time and consideration to her dress (and spent more money on it) than at any other epoch in history. ''She changed outfits several times a day and bound and strapped her body to fit better the ideal silhouette of the year. . . . In 1860, at the height of the crinoline skirt period, she required four attendants armed with poles just to put her skirt on,'' according to a text that accompanies the exhibit.
Such slavish pursuit of the mode required a steady stream of up-to-date documentation. In times when the means of communication were far slower than today, the journals of the mode from Paris and London (Berlin and Vienna, too) provided the guidelines for ''proper'' attire.
The stylish way to dress for every occasion and every hour were all regularly depicted in their latest forms in such widely circulated publications as La Belle Assemblee, Ackerman's Repository of the Arts, Le Follet, Wiener Moden, Le Petit Courrier des Dames, and La Revue de la Mode. The format of one of the most exquisite 19th-century magazines, Le Journal des Dames et des Modes, was duplicated for a brief period before World War I with the same high quality engravings on handmade rag paper. Plates from La Gazette du Bon Ton, which was issued from 1912 to 1914 and from 1920 to 1925 (they now sell for from $25 to $ 75), are particularly desirable. It was possibly the most beautiful fashion magazine ever published.
Not everyone will choose to acquire prints that simply tell the story of the fluctuations of style - which is what the Cooper-Hewitt exhibition does - by going from Empire to French Restoration (when skirts were short enough to show pantalettes) to hoops, and on to first bustle, second bustle, monobosom, Poiret, Vionnet, and Chanel. Neither will everybody wish to amass as many prints as Vyvyan Holland, the son of Oscar Wilde. The demon collector of all time, Holland presented his trove of 9,000 prints to Cooper-Hewitt; selections from this legacy make up most of the exhibits.
A different approach might be to concentrate on examples by various artists. For starters, there could be a 17th-century steel engraving by Wenceslaus Hollar; later on, a French Directoire print by Carle or Horace Vernet, and a Restoration-era plate by Gavarni. Anglo-French illustration in the latter half of the 19th century was dominated by Jules David and by the family of Alexander Colin. His three daughters, Heloise Leloir, Anais Toudouze, and Laure Noel, all married painters, and their consistently handsome works are enhanced by furnishings and backgrounds that give the fashions scenic perspective.
From more recent times, the artists of La Gazette du Bon Ton would be choice additions. Besides Georges Barbier, whose plates are the most sought after, A. E. Marty, Bernard Boutet de Monvel, Pierre Brissaud, Brunelleschi, Erte, Georges Lepape, and Benito are some of the best. Raoul Dufy, surprisingly enough, also did memorable fashion drawings for the Bon Ton.