What is a bromide?

And why do I need one?

A bromide is a high contrast black and white image on photographic paper. It needs to be high contrast i.e. the black is very black and the white is very white so that a sharp, clear image is produced when a printing plate is made from it. Because the photographic paper has no fibres on the surface the image produced is always razor sharp, and because the image is produced by a chemical change in the surface of the paper the image on a bromide is always a dense black.

A printing press can only print two things-a solid area of ink or nothing, it is not possible to print areas of partial colour. To achieve the illusion of partially coloured areas such as the different shades in a photograph, the image on the bromide is broken up into patterns of dots called halftones. The spacing and size of these halftone dots is varied to suit the type of printing press and paper being used.

A bromide is produced by an imagesetter which is a very high resolution printer that outputs onto photographic media. The imagesetter must have a high resolution so that it can properly form the halftone dots and also reproduce type at small sizes without the characters becoming jagged.

Sometimes you can use a laser or bubblejet output as a master for printing as long as you don't have any small type, fine halftone areas or photographs and you make sure that the blackness of the ink or toner is very dark and the paper is fairly white, but to get the best result from any printing work you are doing it is best to use a bromide.

Sometimes, for very high quality work, your printer may require negatives, which are also produced by an imagesetter using a clear photographic film rather than bromide paper. Printing plates made from negatives can hold finer detail and larger solid areas than the plates made from bromides.