Expansion ~ Compaction Negative Control

There remains old terminology in photography like "overexposed" or "underexposed" to denote the level of recorded light upon the negative. This is but one variable in a three variable relationship. The amount of light is only over or under exposed if, and only if, the developer, its dilution, and the development time remains constant. That would be a shame, as there are variations upon the theme for mixing these three variables to arrive at the contrast index/density range, desired.

Redefining the variables; 1) amount of light given the negative, 2) developing agent, 3) dilution of the developer. One of the primary reasons the third variable is seldom if ever used is simply because most photographers continue to use pre-packaged developers and dilution is not a normal part of that setup. Pre-packaged developers were meant to use as is. Because of this, I restate that this article is based upon mixing your own chemistry, and can therefore control dilution levels of the developer.

As was covered in the previous article on "Time & Dilution", those are two of the variables available the photographer. The third leg of that calculus is how much light to give the negative before adding the other variables. Back in the day, I was most interested in visual texture of the image, printing silver gelatin prints. To maximize texture of an image it is beneficial to have the contrast index curve favor the higher densities, another way of describing pushing the densities up to the shoulder of the curve. My method of doing that was "overexposing" the negative by setting my ISO from ISO 125 to ISO 80, ISO 400 to ISO 320. To compensate for that in order not to blow out the upper end of the densities (highlights) I reduced the development time slightly (approximately 1 min), or, I diluted the formula.

That method is referred to as a 'compaction'. Compacting the tonal range by holding back the upper tonal ranges from Zone 6 thru Zone 8, which are the tonal ranges that are affected by development, either more or less. Zone 5 down, remain unchanged by further development, after they have reached their maximum density during development. The rough calculus for this arrangement is 1 min reduction in development for every stop over the standard constant. If you overexpose one stop, a one minute reduction in developing time compensates for the 'overexposure'.

Reciprocally, an expansion is the reverse of this, when an image is 'underexposed', lacking sufficient light on the film to arrive at a full scaled negative that otherwise would have been in a printable range had it had more light. Again, for every stop under normal exposure, adding one minute of developing time increases the upper densities to arrive at a longer tonal range (density range).

Compaction: Reducing the development time:
N-1 = 1 min less development   ~ N-2 = 2 minutes less development

Expansion: Adding to the development time:
N+1 = 1 min more development  ~ N+2 = 2 minutes more development

The uses for this method is simply to offset lighting conditions when they are not optimal. When confronted with a flat day of less than five stops, be it a rainy day or just soft flat lighting, meter the scene for an average, stop down one, or two stops, then shoot. When developing, use the N+1 or N+2 developing times, respective of the number of stops used when shooting. This stretches out the contrast index curve, increasing contrast proportionate to the N-factor used during shooting & developing.

Conversely, the opposite can be used when it is very high contrast shooting. By reversing the procedure, there is the option of simply reducing the development using N-1 or N-2 times, the upper densities (highlights) can be held within a printable range. One can also 'overexpose' just a bit for more shadow detail, which would then require a more robust use of the N-2 development to keep the upper densities from becoming too dense to print well.

For any of the above to be of any use to the photographer, film testing is necessary. The photographer needs to know what the baseline is for that film, lens and developer/development time being used. That is easily done using the towel test. That is next. An example of an image using compaction is below. It was shot in my home studio space I built around an existing carport. The front window of that studio area is seen in the image. The view is north, thus true north lighting, which still was quite different than the ambient light inside the studio. I exposed one stop over standard meter reading, then used the N-1 development to hold in the brightness through the window. Then there's the visual translation from the scanned slide and the digital representation I arrived at with the image. Forgive the loss between the two images.

Silver Gelatin Print ~ "Studio Light"
1986 ~ 8"x10" ~ Unique
Eugene, Oregon