For the sake of variety in a collection, or to cut out part of a defective print, photographs are sometimes trimmed to circles or ovals (ellipses). Such fancy trimming, however, should be used with restraint. A profile head may suitably be trimmed to a circle, after the manner of a medallion, or a half-length portrait may be cut to an oval.
Professional portrait photographers for many years bound themselves to the exclusive use of a certain number of standard sizes, enumerated below, but from which, in recent years, they have cut completely adrift, at least as far as concerns the outside size of the mounts 704. Trimming. The trimming of prints is usually done with a shearing blade or cutter, operated by hand or foot. The usual pattern is one in which the cutting blade is fixed to a base on pivots which allow it to swing to and fro slightly. The print is placed on a bed which butts against the blade by the operation of a spring. On the bed being pressed down against the cutting edge of the blade, any margin of print projecting from the bed is cut cleanly off. Those models are to be preferred which comprise a squared guide or a bed ruled in squares, the object, in either case, being to ensure rectangular corners when trimming. The alternative means is to use a cutting tool, guided by a rule or set square of glass or steel. 2 For this is used either a bookbinder's knife, fixed in a handle with a tightening screw, or a penknife, or a vaccination lancet in the form of a pen mounted in a stout penholder. Whatever may be the tool chosen, it should be frequently sharpened on an oilstone.
The transparency of trimming shapes and set-squares of polished glass is an advantage, but there is always a risk of their slipping over the print during cutting. Moreover, there is no need to see the picture if the cutting line has been determined beforehand (§ 703). Ground glass set-squares, which are sometimes used, have no advantages over those of steel. In order to prevent steel rules and set-squares from slipping over the print it is a good plan to roughen the under side with glass paper or emery cloth. Rules and set-squares made of wood or ebonite should not be employed ; they are liable to get chipped and so be rendered useless.
When photographs are trimmed to a certain number of set one uses a cutting shape made of glass 2 or metal (usually zinc). The glass shapes are generally made with roughened or ground surfaces, with or without a squared scale, to facilitate placing in the correct position. The metal shapes are generally made in the form of a mask, the cut being made along the inside edge.
For trimming, the print should lie on a fiat bed, soft enough to avoid the necessity for frequent sharpening of the tool. The best cutting beds are those of wood, made with the surface at right angles to the grain of the wood, as is done in the case of butchers' blocks ; cuts made by the trimming knife thus disappear on wetting with water. Sheets of roofing zinc are often used (if new, they should be roughened to prevent slipping). The disadvantage of glass is that it very quickly blunts the tools. Again, the bed may be a sheet of cardboard or a pile of waste sheets of paper.
For trimming with a shape it is convenient to use a trimming table, consisting of a board turning freely on a vertical axis.
Trimming to a circle 3 or oval is usually done by means of glass or zinc shapes, which may be bought in various forms and sizes ; a wheel cutter is used with them. The wheels are not usually re-sharpened, but are replaced as needed.
Prints may be trimmed wet, using glass shapes and a wheel cutter, laying the prints face down on the glass.
Trimming with the deckled edges sometimes adopted for prints with wide margins on coarse grained cards, and obviating the necessity of mounting on cardboard, is often done by the manufacturer of the sensitive paper, the sheets being left as they are, precautions being taken not to damage the edges.' Photographs printed in large numbers are, preferably, cut up in piles on a guillotine. For this it is necessary that the various sheets are piled in such a way that the pictures are exactly superposed, either by bringing two sides of each sensitive sheet against fixed studs when printing them, or by punches on the bed of the printer by which each sheet is perforated, these perforations allowing of the finished prints being registered on the bed of the cutting machine.