Densitometry for Ilford HP5 Plus developed in Rodinal

This data represents my efforts to reach and maintain optimal wet-lab processing of Ilford HP5 Plus black-and-white film using Rodinal developer.

The test exposures were made using 35mm film. Thirteen frames of the film were exposed to a blank white wall, or equivalent. Using the photographic zone system as a guide, the frames were bracketed in one-stop increments from Zone 0 (approximating film base) through Zone V (gray card) to Zone XII (approximating maximum density). My guide to this process was Ansel Adams’ The Negative. (See Appendix 1 – Film Testing Procedures, pages 239-244.)

Processing of the film was in Rodinal film developer marketed in Canada as “Blazinal.” The Blazinal product label indicates Compard (Germany) as the manufacturer with product number AFRO15, corresponding to Compard’s R09 One Shot packaging for Rodinal.

The developer concentrate was diluted 1+50 with distilled water. Various unverified sources indicate that a minimum of 10ml of Rodinal concentrate per 35mm, 36-exposure roll (or equivalent) is necessary to prevent developer depletion. My own tests appear to confirm this. Thus, one 35mm roll of film would require 500ml of working developer.

The results shown here are based on film processed on November 10, 2013. The film was processed for a time of 9:00 at a temperature of 22ºC. According to Ilford’s time and temperature compensation guidelines, this would be an equivalent of 11:00 at 20ºC. However, Ilford’s guide does not indicate the temperature coefficient–that is, the variance in reaction time with changes in temperature–a factor that varies by developer. Using a known temperature coefficient for Rodinal (2.0), the equivalent development time would be 10:00 at 20ºC.

A Paterson System 4 tank was used for processing. Initial agitation was one inversion every two seconds for the first 60 seconds. Subsequent agitation took place every 60 seconds with one inversion every two seconds for ten seconds.

An acid stop bath was used along with a two-bath fixer.

Densitometric readings were taken with a Tobias TQ+ densitometer. Results were plotted in a spreadsheet and graphed, as shown below.


In this graph, the horizontal axis plots target zones from film base plus fog (FBF), through Zones 0 and XII, and then maximum density (Dmax), if available. The vertical axis plots the measured film density as determined by the densitometer.

The pink line indicates normal development assuming an EI of 400. The orange and yellow lines represent one-stop over- and under-exposure, respectively. The black dashed line represents a film development curve from data recommended by Ansel Adams (1981, p. 220). The grey dashed line would represent the manufacturer’s suggested curve, however, none was found to be available. The blue line indicates a film development curve as suggested by data provided by Lambrecht and Woodhouse (2010, p. 507).



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