Slides and color negatives can be duplicated using the same techniques. The best way to duplicate both is to use a computer. Scan the original in using a scanner that can go to a high resolution (2000-3000dpi or more) and that has high-density level specification (3.6 or better). Drum scanners are best, but very acceptable work can be produced on dedicated film scanners and some high-end flat-bed scanners. We use the Nikon Super CoolScan 2000 for all of our 35mm and APS film work. We use the UMAX PowerLook III for scanning our medium format film. Once the image has been converted to digital data, it can be stored on CD-ROMs. Such storage pretty much stops the clock on any further deterioration of the image. Meanwhile, the original silver halide image will, of course, continue to slowly deteriorate.
Having said that, if you are dead set on doing things the traditional way, here is how I used to duplicate slides and color negatives in my darkroom.

Duplicating slides and color negatives can be done with two types of film: 1) real duplicating film, and 2) regular camera transparency film. There are pros and cons to using each type of film.

Making Duplicates Using Duplicating Film. Kodak and Fuji make excellent duplicating films. Kodak makes several different kinds of duplicating film designed to fill the needs of specific problems. Fuji makes one duplicating film that is sort of a catchall product. Personally, I like the Fuji product. It can be used with quartz halogen or electronic flash illumination. One of the Kodak products--Kodak Ektachrome Slide Duplicating Film, No. 5071--can also be used with either type of illumination. If I were to use a Kodak product, that would be my choice. Kodak No. 5071 is a rollfilm product that is available in 35mm, 46mm, and 70mm sizes. The sheet film version of it is called Kodak Ektachrome Duplicating Film No. 6121, and is available in sizes of 4x5, 8x10, and 11x14. Fujichrome Dupli-cating Film CDU Type II is available in 35mm, 70mm, and sheet sizes of 4x5, 8x10, and 11x14.

Aside from the type of duplicating film that you will use, you will need to decide on what type of equipment you will use.

I would suggest that the best way is to use equipment that has been especially made for that purpose. I like the Beseler Deluxe Dual Mode Slide Duplicator, Cat. No. 4120. It has several nice features. It offers a choice of quartz halogen or electronic flash illumination. The color filtration can be adjusted with either type of illumination. It has a built-in method of inducing a controlled fog to the duping film for contrast control. It will accommodate original films up to and including 4x5 with an optional accessory. Duplicates can be made onto 35mm film using a 35mm camera body of your choosing. I've had people tell me that they were able to jury-rig a medium format camera onto the machine.
However, if you need to make duplicates (or copies) that are going to be larger than 35mm, then I strongly suggest that you need to use a color enlarger and buy duplicating film in sheets.

The Beseler Deluxe Dual Mode Slide Duplicator requires that you furnish your own 35mm or medium format camera body to hold the duplicating film. You will need to get from Beseler the correct adapter ring for your brand of camera. You will need to buy a duplicating lens to use. A 75mm (or longer) duplicating lens is required. APO lenses made for use on enlargers are best. Regular enlarging lenses are next best. I would avoid using regular camera lenses. You will also need a cable release for the camera that you are using.

If you are doing 35mm work, I would buy the 35mm duplicating film in 100' rolls and manually load empty 35mm cassettes. You will need several cassettes of film to use for color balance and density testing and setup before making any acceptable duplicates. You will have to have a sufficient supply of the film in a matching emulsion batch to allow you to do the testing and the final production work.

You can send the E-6 processing to an out-lab or do it yourself. In either case, be sure the processing is done carefully and correctly. Inexpensive out-labs are not recommended. Their results vary too much from day to day.

Establishing Color Balance And Density. You will need to decide if you are going to use quartz halogen or electronic flash illumination.
Quartz halogen illumination is commonly used because most duplicating films have been optimized for use with that color of light. However, when using quartz halogen lighting, your exposure times will be naturally long. This can present some problems in getting the correct density set for the exposure and can possibly result in blurred duplicates due to slight vibrations during what will be a rather long exposure.

I prefer to use electronic flash illumination. The Beseler Deluxe Dual Mode Slide Duplicator allows you to further tweak the color of the illumination using conventional, dial-in, dichroic filters. Since the Kodak and Fuji duplicating films will allow you to use electronic flash, I think it is the best way to go. Set your camera's focal plane shutter for the correct synchronization and then adjust the lens' f/stop for the correct density. Use a starting filter pack of +65Y --15C plus the data on the box of film when working with electronic flash illumination and duplicating film.

Make a series of density exposures on to a test roll of film. When using electronic flash illumination, set the camera shutter to "X" synchronization, and make a series of test exposures in 1/2 or 1/3 f/stop increments.

On the Beseler Deluxe Dual Mode Slide Duplicator there is a setting to control how much "fog" feedback the device allows onto the film. This amount of fogging is crucial to controlling the contrast level of the duplicated image. Use the "X" setting (no fog) on the Contrast Control module for the first series of tests. If you do a real critical evaluation of the duplicated image, I expect that you will find that most duplicating films (Kodak and Fuji) will probably produce images that are a tad too low in contrast. You might be able to deal with this by carefully underexposing the E-6 film and then push processing it. Try a one f/stop underexposure and a one f/stop push process. If that trick doesn't solve the problem, you may want to consider doing your duplicating with regular camera film where you can carefully adjust the contrast by using the fog control setting. More fog will produce a lower contrast.

After you have processed the first roll of test exposures, examine them carefully and select the image that produced the best density. Then, evaluate that image and make a decision on how to adjust the dial-in filters for color balance adjustment. Then, crank in the estimated color filtration adjustment and do a series of color ring-around exposures in 5cc increments based on the new estimated filter pack. Process the roll of film and re-evaluate the results. You will probably have to make several such test rolls of film in order to get zeroed in on the correct density and color balance.

The original slides or negatives that you want to duplicate should be sorted into groups of film type and age. Older images will have faded a bit even if your eye can't detect it. Such fading will reproduce and require a little color balance tweaking. Different brands of film will also perform differently and require slight color balance tweaking.

For doing your setup testing, select an original image that includes lots of nice neutral gray tones (not the Ektachrome blues) and that also has some delicate, pastel, highlights and some deep, dark, shadow tones. Use the neutral gray tones to judge the accuracy of your color filtration settings. Use the highlights and shadow tones to judge the accuracy of your density and contrast control.

When you finally have the best settings that you think you can get, proceed to make your duplicates. Then, examine the finished duplicates carefully. You will probably find that about 80 percent will be acceptable. The remaining 20 percent will have to be remade with some slight tweaking for each one. That's about normal.

Making Duplicates Using Regular Camera Film. You might want to use regular camera film if you have had trouble getting the contrast high enough when using real duplicating film.

If you decide to use regular camera film, be sure to use a slow speed daylight type of transparency film. With electronic flash illumination, use a starting filter pack of: +20Y +30C. Set the camera shutter to "X" synchronization, and make a series of test exposures in 1/2 or 1/3 f/stop increments.

Use the "X" setting (no fog) on the Contrast Control module for the first series of density tests.

After you get zeroed in on the correct density level, proceed to adjust the color balance and, as you get pretty close to the final settings, begin to evaluate the contrast of the image. The contrast will naturally be too high when using regular camera film. So, start making tests using the fog control settings by cranking in a little controlled fog. The Beseler Deluxe Dual Mode Slide Duplicator offers 11 different fog settings to choose from. You will very quickly determine how much fog is just right for the contrast level that you want in the duplicate image. All of this trial and error testing will consume several rolls of film.

The E-6 Process. A well controlled, properly maintained, E-6 process is absolutely necessary if any of the tests are to mean anything. The full, seven-step, E-6 process is strongly recommended instead of the shortened, three-step systems.

I believe that the three-step systems are more susceptible to local water conditions and shelf-life aging than the seven-step systems, but those problems need to be controlled for all types of E-6 processing.

I strongly recommend that you include E-6 control strips with all process batches of duplicate slides as a check against potential E-6 processing problems. Use Kodak Control Strips, E-6, No. 151-9750 (box of 50 strips) or Kodak Control Strips, E-6, No. 122-6554, 35mmx100'.

If you'd like more detailed help with your duplicating, you can send me e-mail at: editorial@shutterbug.net or write to me care of Shutterbug.

Tips For Making Duplicates
· Slides and color negatives can be duplicated using the same film and techniques.
· You can use duplicating film or regular transparency camera film.
· You can use quartz halogen or electronic flash illumination.
· APO enlarging lenses are best, but regular enlarging lenses can be used.
· Careful trial and error testing for density, color balance, and contrast are required.
· Duplicating films may produce too low a contrast.
· The contrast of regular camera films can be lowered by using controlled amounts of fog.
· Accurate and repeatable E-6 processing of the duping film is a must.