SLIDE DUPLICATION

by Fred Roberts ARPS 

From the April 1997 issue of the North & East Midlands Photographic Federation Newsletter (No. 61), with the kind permission of Editor, Peter Cheetham for reproduction here.

On retirement I invested in a Kaiser Colour enlarger and the accompanying literature gave details of using it for slide duplication. I had always been interested in the latter using an Ohmar zoom copier with flash diffused by a white card at 45o and exposure regulated by the distance from the flash to card then back to the camera. The results were reasonable but the set-up was a bit fiddly, so I decided to buy the special Kaiser kit which consisted of a well engineered camera bracket to fit on to the enlarger column and a plastic tray with light traps to accommodate the complete inverted colour head. A 2" x 2" slide insert fits neatly into the carrier assembly but there is a tiny leeway in the fit of the latter so the slide should be gently pushed in the same horizontal and vertical direction for each exposure to achieve perfect placement. Further to the latter I selected a very dark negative (over exposed lith is perfect), taped it over the perforations to a board then, using a Stanley blade at an angle and a steel rule, scraped the two diagonals on the 36 x  24 format followed by three lines at 2, 4 and 6mm from  each of the four sides then mounted it as a permanent check slide. 

Originally I used a Spotmatic with a  50mm macro lens plus a 300mm extension tube to bring me down to 1:1 but since then I bought a Pentax Z1 and a 100mm macro lens which are perfect for the job. It is used at full macro range and, strangely enough, I use the Kaiser crank, which has a firm friction drive, for precise focusing. 

Turning now to film stock, several years ago a friend gave me 15 yards of Fuji CDU to experiment with and I have stuck with this brand ever since. I have no doubt that Kodak and Ektachrome dupe film are every bit as good but up till recently Fuji was the only option for bulk loaders and is still less than £50 for 30 metres i.e. 19 rolls of 36 exposures. I find no problems with extreme contrast and do not need to use any pre-flashing methods and the grain is very fine. 

Re Bulk loading I must mention a little tip I learned from an article  in the S.P.F. Bulletin written by Steve Dunning ARPS. Where the loader has a mechanical circular light trap take a Stanley knife and cut out a section of both leading edges about 3mm deep by 24mm in the centre area which the film slides over. As the film is wound off the central spool it will rest only on the perforated edges and tramlines will miraculously disappear. 

The next step is to assess the dupe film for colour and exposure. At this stage a working knowledge of E6 processing is very handy as short rolls of a dozen exposures can be wound off and processed immediately. Failing that a 24 exposure is the only economical answer for a processing lab. Speed must be fine tuned before colour is adjusted as the former has a bearing on the latter result. I would suggest setting the colour head at an average of 30 cyan and 30 yellow then making exposures from F11 to F22 at both a half second and one second. Comparison against the original on the light box should reveal the correct exposure. 

Opinions vary as to the best type of slide for using as filtration check. A well exposed church stained glass window has helped me with a myriad of colours but a landscape quickly shows any faults in blue skies and green foliage. Normally contrasty slides are not suitable. Some purists argue that filtration should be altered to accommodate any bias in different film brands but I have never found this necessary. Start at ten units of cyan and yellow and increase these by five units up to a total of 40 with as many different combinations as possible on a 36 roll, making a careful note of each setting and frame number. Once again the light box should reveal the best compromise and might even suggest some further small adjustments. As a matter of interest my present setting is half a second at F19 with a 36 cyan and 34 yellow. All this may seem a tedious task but you now have a setting which is valid for 30 metres. With a large run of dupes stick with this exposure and filtration at all times for ordinary copies ignoring the fact that the originals may be dark or light. However, on the creative side, experiments with filtration can add atmosphere and under exposed slides with good detail can benefit from one to two stops extra. 

To recap:- 

Set up camera at 1:1. 

Using the scratched register slide, use anti-static brush on slide to be copied and insert using slight pressure as directed. 

Turn off all darkroom lights. 

Exposure using a cable release or in built delay. 

If copying a large number for an exhibition for example always repeat the last slide on a cassette as the first slide on a new one. 

Finally, my work is done on a Kaiser enlarger but Durst and some  other manufacturers supply their own kits.