Magnifying frame

A magnifying frame is a device used to hold photo paper firmly under the enlarger . This is necessary in order to be able to enlarge a negative to the intended image size. On the one hand, the photo paper is kept flat in order to preserve the depth of field without unnecessary stopping down ; on the other hand, the photo paper is secured against slipping and finally, evenly straight, white picture edges can be created on the sides of the picture. For this purpose, magnifying frames have adjustable masking strips that cover the edge areas that are not to be exposed. In borderless enlarging frames, the sheet of photo paper is not fixed with the help of the masking tape that creates the edges, but rather by a glass plate .

Magnifying frames with a perforated surface are particularly elegant : behind the passage openings there is a housing with a connected vacuum pump (self-made vacuum cleaner ). The negative pressure created in the housing sucks the photo paper onto the surface of the frame. In a professional environment, this solution can be found in prepress , more precisely in reproduction cameras that process negative sizes of up to 30 × 40 cm. The disadvantage of this construction , however, lies in the power consumption as well as in the noise and heat development .

In the horizontal projection , used when enlarging on the largest scale, one uses an enlarging frame attached to the wall, up to several meters wide, on the top of which a suspension for rolled goods and a cutting device is already attached. So large enlargements are feasible.