With or Without Pre-soak?

Objective

To try to determine if there is any difference between a film processed with and without a pre-soak


Exposure Method
The film used was a roll of 120 sized Ilford FP4 Plus with an expiry date of April 2009. For convenience it was rated at 100 ISO. This gave a good correlation between speed and stop without having to estimate thirds on the aperture scale.

The camera used was a Rolleiflex 3.5F focused on infinity to take out any variation due to ‘bellows’ effect.

The Target was a piece of mid grey mounting board lit by north light from a north facing window. The light was constant throughout. The camera was positioned so that the card filled the full negative area.

The meter was a Pentax Digital spot meter. The reading of the card was 8, which at 100 ISO gave a Zone V exposure of 1/15 sec at F4.

The film was then shot as follows:

Frame   Zone     Exposure Given
  1.    Zone V    1/15 @ f4
  2.    ZO        1/15 @ f22
  3.    ZI        1/15 @ f16
  4.    ZII       1/15 @ f11
  5.    ZVIII     ½ @ f4
  6.    Blank
  7.    Blank
  8.    Zone V    1/15 @ f4
  9.    ZO        1/15 @ f22
  10.   ZI        1/15 @ F16
  11.   ZII       1/15 @ f11 
  12.   ZVIII     ½ @ f4

The meter reading was checked at the end of the shoot showing no deviation.


Development
The film was split into 2 halves and each half loaded into a development tank. It was then processed as follows.

Part 1 Processed in ID 11 1 + 1 at 20 oC for 7 minutes 30 seconds. The film was agitated by inversion constantly for the first 30 seconds followed by a rap on the working top. It was then inverted once each 30 seconds for the rest of the development time. Following development a stop bath of Ilford Ilfostop was used for 30 seconds at 20oC. This was then followed by 10 minutes in Ilford Hypam at 1:4 again at 20 oC agitated at 5 minutes.

Part 2 This received a 5 minute pre-soak in plain water agitated by 1 inversion each minute. The film then received the same treatment as Part 1.
I checked the temperature of the developer at the end of the processing time. Without the pre-soak it was 19.7 oC while with the pre-soak it had remained at 20 oC. The room ambient temperature during development was 18.9 oC. All temperatures were measured with a RH Designs digital thermometer.

The films were washed by the Ilford method and hung to dry.

Readings
The following density readings were taken using the densitometer feature built into the RH Designs Analyser Pro.
The negatives were placed in the carrier of a Durst M605K using the 6x6 film mask. The lens used was an 80 mm f4 Schneider Componon S and the lamp was allowed to ‘warm up’ for 5 minutes before any readings were taken.
Initial readings were of base fog above the enlarger light level with no film in the carrier. They were without pre-soak - 0.1 and with pre-soak - 0.08.

The meter was then zeroed on base fog and the following density readings taken and so are above base fog.

Negative   Without      With
           pre-soak   pre-soak
  ZO         0.2        0.17
  ZI         0.37       0.30
  ZII        0.54       0.42
  ZV         1.09       1.06
  ZVIII      1.82       1.83

Conclusion
While this is not a definitive and exhaustive test it does show that there is a difference between with and without pre-soak. Those without seem to give a denser negative, which suggests that the pre-soak does have a diluting effect on the developer albeit small. This may be offset by the developer holding its temperature better because the pre-soak is building heat into the tank which helps maintain the developer temperature. This should help to improve consistency between films.

From the density readings it looks like I am over exposing and over developing my films or the shutter is running slow. This will be the subject of further personal testing.

All tests reflect the equipment and working practices of the person doing that test. Similar test by other people may give different results.