Using an Enlarger as a Copier

By Ken Smith (Area 4).

Making duplicate slides, colour negatives from slides, monochrome negatives from slides or black and white slides from black and white negatives can be very rewarding. If one is lucky enough to have an Illumitran none of these procedures present a problem although for best results a flat field macro lens should be used.

Recently I needed some copy slides and, after pondering for a while, realised that my 35mm enlarger and SLR could easily be adapted for the procedure. An enlarger is ideal for evenly illuminating a 35mm slide or negative and an enlarger lens is computed for a flat field at close range. So I set about making trials and finally came up with the following method which has proved very satisfactory.

The basic principle is to use the enlarger to project the image from the slide or negative to be copied onto the chosen film loaded in a SLR camera body with its lens removed. A clear view of the image can be seen through the camera viewfinder and this facilitates framing and focusing.

Now, the vast majority of enlargers operate vertically and if the camera is to receive the projected image it would take a contortionist to see through the viewfinder. The answer is to detach the enlarger column from the baseboard and remount it horizontally using home made brackets. With a little bit of inginuity the bracket which is to support what was the base of the column can incorporate an adjustable mounting for the camera. Enlargers differ a lot so the design of brackets must vary to suit individual models but the sketch from my last article shows the arrangement for my Durst 300.

To ensure maximum adjustment for framing and degree of magnification it is advisable to incorporate both vertical and lateral movement of the camera in relation to the enlrager lens axis. The support for the "top" end of the column can be a simple foot drilled out to a sliding fit on the column.

In operation the material to be copies is mounted in the negative carrier of the enlarger and with the enlarger lens at full aperture the camera can be aligned with that part of the image chosen for copying. Focusing is acheived by a combination of the enlarger lens adjustment and the racking mechnaism. With some enlargers it may be necessary to fit an extension tube behind the lens to get down to 1:1 magnification but to enlarge part of an original presents no problem. Once a satisfactory image is acheived the lens is topped down to F8 or F11 to optimise its performance and exposure is made using the camera shutter.

Exposure deteminiation is a very personal control as there are several ways of approaching the problem. It is possible to use an enlarging meter in either spot or intirated mode by holding the sensor and close to the film plane as possible. With some cameras, usually those with shutter priority mode, it is possible to use the TTL metering system even when the camera lens is removed. However, cameras which have programme or aperture priority modes require the aperture to be indicated to the metering system before it can compute the exposure. In any event it pays to bracket exposures at least for initial tests. As a rough guide for a starting point using ISO 100 film try 1/60th sec. with apertures between F8 and F11.

When copying it is inevitable that contrast will be increased but home processors can control this during development. For colour slide duplicates try increasing exposure by 50% and reducing first development by 30%.

In the previous article on producing black and white slides from black and white negatives the developing time was inadvertently missed out. For Technical Pan 2415 rated at 200 ISO the time is 8 mins. at 20C in Kodak D19B developer with four inversions every 30 secs.