F YOU browse through the advertisements for secondhand plate cameras in old photo magazines you often find cryptic abbreviations such as BFDS, DDS, SMDS, CFS, FPA and RFA. Plate cameras have been obsolete for so long now that many people have no idea what these abbreviations mean. They stand for book form darkslide, double darkslide, single metal darkslide, cut film sheath, film pack adaptor and roll film adaptor.
     Some people call darkslides plate holders, but in the days when plate cameras were popular photographers made a distinction between the two. Plate holders were just that, a frame to hold the plate in the camera, and had to be loaded into the camera in the dark. Each time the plate was changed the camera had to be taken into the darkroom or put in a changing bag. Darkslides as the name suggests had a slide to reveal the sensitised side of the plate. They had to be loaded in the dark but a number could be taken on a photographic outing and the slide pulled out after fitting them in the camera and just before making an exposure. To save having to carry a large number, they were often double sided. Between the two plates was a thin sheet of black metal with a leaf spring each side to keep the plates pressed against the focal plane.
     Book form double darkslides are beautifully made, usually from mahogany,

Pictures fror this page to come

and are often found with large format brass and mahogany cameras from the 1800s and early 1900s. As the name suggests they were made to open like a book, and a plate was loaded into each side. The slides were also made of mahogany and weren’t taken right out before making an exposure. They were pulled as far as a stop and folded on a cloth hinge so they didn’t stick out from the camera. These cameras and the darkslides were hand made by craftsmen many of whom had served long apprenticeships as cabinet makers. They weren’t entirely entirely hand made in that woodworking machinery was used for the basic cutting out and cutting of rebates for the sliding parts, but they were hand assembled and fitted, and finished in a rich French polish.
     Book form darkslides were quite expensive, so to provide something cheaper the double darkslide was introduced. These didn’t open for loading, a plate was loaded from each side and held by rebates top and bottom. One of the rebates was deeper and had a leaf spring inside so that the plate was pushed up against the leaf spring which then pushed it down into the bottom rebate. It wasn’t unknown for the plate to jump out of the rebates if the darkslide was dropped or even tapped smartly on the top so locking devices were introduced to prevent this. A neat arrangement on the Kodak darkslides for its Premo cameras was a spring loaded bar in the top rebate controlled by two small plunger catches outside at the top.      When these catches were locked there was no chance of the plate being dislodged. Double darkslides rarely had wooden slides.
The slides were made from thin sheet metal, or in some cases a thin sheet of vulcanite, and were taken right out before making an exposure. A velvet light rap at the top saved the plate from being fogged when the slide was taken out. The divider between the plates was often made from thin black card. This, and the vulcanite slides had the advantage that they didn’t get spots of rust, as the thin sheet metal ones often did, but the vulcanite slides were very brittle, and you often find them cracked or broken.
     In the 1920s wooden darkslides gave way to much cheaper single metal darkslides which could be mass produced by machinery. They held just one plate each, but they were cheap, and they were slim so more could be carried in a camera bag – if you didn’t mind the weight. Metal darkslides weren’t often made much larger than 5x4 inches, but they went right down to VP, 6x4.5 cm.
     When cut film was introduced in the same sizes as glass plates it had the advanatge that it was much lighter and didn't get broken as glass plates often did. But though it was thicker than roll film it was still too floppy to be loaded into a drakslide by itself, and the leaf spring to keep it in the focal plane would scratch the film. Instead, you loaded the sheet of cut film into a metal sheath, a sheet of thin metal with turned-over edges on the sides and bottom, and used this in place of the plate. With these sheaths you can still use your plate camera because cut film is still available at the time of writing from specialist suppliers though the range of sizes is restricted. If you're ever loading cut film in the darkroom it's easy to forget which is the emulsion side. Most cut film has two or three notches in the shirter side to identify the emulsion and film speed. If you hold the film so that the nothes are at the top right or bottom left, the emulsion side is facing you. On the few occasions you come across cut film without notches, moisten your lips and put just the corner of the film between them. The side that sticks to your lip is the emulsion side. You can't do this, of course, if you're using a changing bag.
     Film packs, using sheets of cut film with interleaving, were much more convenient than glass plates and had the advantage that film didn’t get broken, as glass plates often did. The sheets of film were bought ready loaded into a card or paper pack, and pulling a tag on the top brought a fresh piece of film into the focal plane. The packs fitted in a film pack adaptor which was used in place of a darkslide, so the photographer had to carry only one adaptor and several packs of film to be able to take quite a lot of exposures on an outing.
     Film packs, however, were never as popular as roll film, and to enable a photographer to use roll film with his plate camera roll film adaptors were made. These held the roll of film in an adaptor which fitted in place of the darkslide and enabled the photographer to have all the advantages of roll film while keeping the versatility of his plate camera with things like double extension bellows, rise and fall, swings and tilts.