Split Filtering

The photographic paper we have been using so far in the darkroom is “multi-grade”, which has been around since the 1940’s. Before this multi-grade, paper used to come in 5 grades, each one varying in the level of contrast. A grade 1 paper would be used to ensure detail in the hi-lights is clearly visible. However, it would then have no detail in the shadow areas. A grade 5 on the other hand would do the reverse. Shadow detail would be great but the hi-lights would be blown. A grade 3 would be great for mid tones but hi-lights and shadows would be lost. These single grades of paper had just on layer and would be sensitive to blue light.

Multi-grade is made up of 3 layers with the additional layer being sensitive to green light in varying degrees. By adjusting the amount of green light you can alter the contrast of the image, this is done of course with the use of a magenta filter in the enlarger.

We can however, gain more control of the contrast with the use of split filtering process. Rather than using the built in filter on an enlarger, graded filters can be used to control and adjust the contrast. Filters come in grades that essentially mimic the old single graded papers from 0 to 5. Split filtering is where you would use two of the filters to balance and enhance the contrast of your image.

As part of the Fuji competition I had selected Fuji Neopan CN41 film to use. This was to be printed on colour paper. However, I also took some more images on the roll and took them into the darkroom to print black and white. I have to say that I was extremely disappointed in the results.

After going through the process of test strips for timings and varying levels of magenta to add some contrast the result was a rather flat image. 

I think the reason for this is the design of the film. With an ISO of 400 it is however designed to be very forgiving and can be pushed or pulled anywhere between 100 and 800 without any serious loss of quality and retaining detail in the shadows and hi-lights. The downside to this is a lack of contrast and a flat image

This made these images a prime candidate to try out split filtering on. Our first attempt was not too successful. Steve had suggested that as my first print was at a 10 second exposure, for the split filtering it needed dividing in to two. Five seconds each for the 0 grade filter and 5 grade filter. From the image left however, this came out heavily under exposed. 

After a little experimentation we decided the best option was to do two separate test strips for the hi-lights and shadows. Testing for the different filters worked out much better. The image now has great tonal value through-out but also has contrast and a depth that results, essentially from a double exposure. The final settings were to use 0 grade filter for 15 seconds and then 30 seconds with the 5 grade filter.

Another image from the roll, originally printed image followed by a split filtered version.