Help from the Pros
Les McLean
How it works.
The initial exposure to white light will produce no tone on enlarging paper - it simply eliminates the paper’s inertia to light. Therefore, when exposing the paper with a negative in the enlarger a certain amount of the exposure is not producing tone, and, more importantly, detail. Flashing is a method of controlling contrast by pre-sensitising the paper with an exposure to white light that overcomes the paper’s inertia.
Once the paper is flashed, all units of image-forming exposure passed through the negative will produce tone, therefore less exposure is required. Consequently, because of the reduced image-forming exposure the lower values are less likely to block up, resulting in better separation in the shadows. At the other end of the tonal scale, highlights are improved because, in effect, the paper is getting more exposure to the image-forming light that produces tone and detail. Because the inertia is overcome by the white light flashing-exposure all light transmitted through the negative is ‘working’ to ensure that the detail in the negative is recorded on the paper, hence the lowering of overall contrast and the improvement of detail throughout.
In describing how I make prints using this method I use two terms to describe the light; white light and image-forming light. White light is any source of light that can be used for flashing, for example, an enlarger with no negative in the carrier, or the Paper Flasher (by RH Designs) that I use. However, it is important that you can accurately control the time of the exposure and that the light source will provide constant illumination. Image-forming light is the light projected onto the baseboard by the enlarger with the negative in place.
Two light sources are required; the enlarger, to form the image, and a second source to provide the white light. A second enlarger will do, but I prefer the PaperFlasher, which can easily be attached to the enlarger. I find it quick, convenient and accurate.
A second method is to leave the negative in the carrier and place a piece of diffusing material, such as Opal Perspex under the carrier, although this method will make the flashing exposure quite lengthy.
Making the Pre-Flash Test Strip.
Use a full 8 x 10 sheet of enlarging paper to make your pre-flash teststrip or cut a piece into 10 x 1 inch strips. With the paper held flat in an easel, use a black card to cover a one inch section of the test strip. This strip will receive no exposure and remain paper-base white.
With a pencil put indicator marks at about one inch intervals along the edge of the test strip. Eight to ten should be sufficient. Expose the test strip to white light in the same way you would when making a normal test strip. I use one or two second intervals. Move the card in sequence over the remaining indicator marks, exposing for the chosen time at each one. Process the test strip as normal and after a short wash and fix, dry the strip, either in a microwave over or with a hair-dryer. The maximum pre-flash exposure is the one immediately before the first step to show any tone. All further exposure tests, as well as the final print, should be pre-flashed prior to the image-forming light exposure.
Controlled Fogging.
When faced with a particularly difficult high-contrast negative, where the highlights appear to be completely burned-out, I use controlled fogging to help print in the detail. Fogging puts tone onto the paper, whereas flashing simply eliminates the inertia. A correctly pre- or post-flashed and developed sheet of paper will show no trace of tone, but a pre-fogged sheet will clearly show an even grey tone. How then can we fog the paper and retain delicate highlight detail and not end up with a degraded, flat image?
How to Calculate the Fogging Exposure.
To determine the post-fogging exposure I first make the image-forming exposure on a test strip-size piece of paper ensuring that the paper is placed across the area that requires post-fogging. I then cover part of the highlight area with a piece of card to ensure it receives no fogging exposure - this is used as a reference area after the test is developed. Using my PaperFlasher I then expose the test strip to white light in increments of, say, three seconds - you will need to experiment with different times depending on the size print you are making. Develop the test strip and examine it to determine the post-fog step that provides the information you require in the image then compare with the adjacent area not fogged to see the full extent of the fogging. Having worked out the required exposures using test strips it is essential that the final print is made using the same sequence.