Highlight masking using duplicate transparency film

How to duplicate transparencies and make masks for creative colours and not a computer in sight!
Words and pictures Peter Bargh

While many of the traditional darkroom techniques can be copied, often quite easily using digital techniques with a computer there's one that is quite difficult, even with a program such as Photoshop or Paint Shop Pro, that have layers and versatile blend modes. The technique, known as highlight masking, is also quite difficult to do traditionally but if you have the patience it can produce rewarding images of graphical quality with vivid colours.

What you need
First off you need an idea of what makes a good transparency to apply this technique. I've found items with bold areas of contrasting tones work best. The example I've included here is a perfect example - large areas of glass with bold cross-cutting structures. This, along with the collection of colours in the windows below adds vibrancy around the image. Landscapes with white clouds against deep polarised skies also work well, as do light flowers against dark green foliage.

It also helps if you work with a larger transparency 5x4in gives you most scope, but few of us have the facility to print from this size negative so a medium-format is a second choice. Working with 35mm can be very fiddly and needs extra effort to ensure good register.

You need some lith film to make the high contrast negative. This is made by Kodak and is sold in bulk rolls or sheets. Buying sheets is best as you can cut a piece to whatever size you want, especially if you use medium format. You also need three trays and lith developer to process the film. Have a look at our previous articles on using lith film to find out how to do this. Contact frame or glass to keep the pair of films pressed together while the exposure is made You'll also need some masking tape to attach the two pieces of film together.

Prepared and ready
1 In the dark place the transparency on top of the sheet of lith film and place the clean contact glass over the top. Place this under the enlarger.

2 You will have to do a test strip to determine the best exposure for the lith film. If the exposure is too short only the lightest areas of the image will be masked and if it's too long the masking will affect too many of the mid tones. Once you have determined which exposure appears to work best make a contact exposure. As this is your first attempt at neg masking it's worth, at this stage, bracketing the exposure and making a copy negative with a slightly longer exposure and one with less to ensure that one of the three gives excellent results. When you are more familiar you will become more adept at picking a good exposure first time.

3 Develop, fix and wash the lith contact film and dry fully.

4 Ideally with the aid of a light box, sandwich the transparency and its negative together and adjust both carefully so that they align. You will see all the highlight areas of the transparency become black and possibly a very fine key-line around edges where dark areas meet light.

5 You could now duplicate this sandwich using a 35mm camera with a slide duplicator attached if you have a 35mm sandwich or extension tubes and use a light box as illumination to copy a medium-format sandwich.

You could also crop in tightly and make different selective enlargements. From my example I have been able to make three very different images.