Rodinal Testing

This post looks at how I have established a standard development time for my home-made Rodinal …

Introduction

We film photographers are always striving for consistency so that we can print in the manner of our choosing and bring into effect what we visualise. This means that equipment, exposure and development times, chemistry and technique should be calibrated to the printing paper that is being used. For someone who uses several cameras in different formats and several films, developing agents and papers, the range of possible combinations is large. I calculated mine to be 720 different combinations! It isn’t possible nor necessary to calibrate so many options because once some benchmarks are established, one can interpolate (i.e. guess) untested options.

One of my ambitions is to succeed in fine monochromatic printing so I need some benchmarks. Although I wouldn’t use 35mm film for fine printing, 35mm does give a good test bed from which to judge standards for the larger formats. One of the standards I wish to establish in 35mm format is Ilford HP5 developed in home-made Rodinal in a dilution of 1:50 printed on the new Ilford Portfolio RC paper.

As my Rodinal is home-made, (and my paper is new to me) I reckoned that the first step was to find a standard development time for HP5 in Rodinal calibrated to the new Portfolio paper. I figured that homemade developer would behave differently to commercial ones.

Furthermore, I had problems making the Rodinal. I used the recipe in John Finch’s excellent book ¹ as follows:

Solution A:

• Water at 80C – 625mls
• P-aminophenol hydrochloride – 50g
• Sodium metabisulphite – 150g

Solution B:

• Cold water 350mls – less than 5C
• Potassium Hydroxide – 215g (strongly exothermic: care!)
• Cool water to make 500mls

But I was unable to get all of the P-aminophenol hydrochloride to dissolve despite 30 minutes of stirring in a 80C water bath. It’s possible that the insoluble sludge was an impurity rather than the hydrochloride. I ignored the problem and filtered the sludge out. But it has left me with an uncertainty in that I don’t know what concentration of active agent I have ended up with – hence the need to establish a base development time.

Film exposure

I set up my 35mm camera loaded with HP5 on a tripod at the back of my barn, and measured the subject brightness range of my scene with my spot-meter. This told me there was a range of 5 stops between darkest and lightest areas. I used Ilford HP5 box speed (ISO 400) on the spot-meter. 5 stops is within the range of the film so there would be no need to push or pull the development. I metered the scene for zone 3 in the shadows and took a series of pictures with the exposure as indicated by the spot-meter, followed by an over-exposure of 1 stop and an under-exposure of 1 stop until I used up the film. The procedure is described in Finch’s book.

Calibration is planned with a particular paper in mind. So a standard practice is vital if you are to get comparable results across scenarios. This includes temperatures, agitation in film development, agitation in print processing and so on.

Since I am working with a new developer and a new paper, the initial aim is to get a ballpark print that contains the full range of tonality of the scene (I chose a scene with a subject brightness range of 5 stops for this reason) and shows the accutance effects that I expect from Rodinal in a dilution of 1:50.

I developed 9 frames of the film in my Rodinal 1:50 for 10 minutes at 20C. The 10 minutes was an initial guess. I agitated using the inversion method for the first minute then every minute for 10 seconds (4 inversions each minute) .

The negatives below have been placed on a lightbox and a picture taken with my smartphone. The left hand negative is n-1 exposure, the middle is ‘n’ (400 ISO) exposure and the right hand one is n+1 exposure.

I don’t advise that calibrations for darkroom printing are done through scanning the negatives on screen and observing the results. I have seen a number of people online recommending this. The scanner seems to flatten out the images and increases the grain unless you adjust, in which case you are departing further from the image on the negatives.

Printing

I took my guessed ‘n’ negative (ISO 400) and ran some test-strips on new Portfolio paper under a grade 3 filter, looking only at areas of the negative that would give black (clear film on edge of negative and a small part of the negative itself. I then exposed the negative for this ‘minimum time for maximum black’ and printed, fixed and washed. I used the same exposure time for the n+1 and n-1 negatives. It’s important not to adjust the enlarger exposure times to produce a more pleasing picture at this stage as this would defeat the object of the exercise.

Below is a scan from print of the ISO 400 negative. The only adjustments made have been to correct for the green tinge that is not evident on the actual print and to reduce the contrast a little to visually match the actual print. Scanning prints seem to increase contrast.

That’s an acceptable result, perhaps slightly losing the highlights:

• The tonal range of the scene has been captured by the film/paper
• There is shadow detail – I metered for zone 3 in the shadow of the barn door
• There is quite high acutance.

I have not shown the ‘n+1’ and ‘n-1’ prints as they just show darker and lighter versions of the above.

Conclusion

My home made Rodinal at a 1:50 dilution does the job required for 35mm HP5 at box speed. It takes 10 minutes. This gives me a ballpark development time to work around. It is faster than I anticipated – I had been expecting a time in the range of 12 to 14 minutes. One reason for this is that I might have added to much alkali in making the Rodinal. As you slowly add the Potassium Hydroxide you are meant to stop just as the solution clears. I was a bit heavy handed with it, so my Rodinal is perhaps more vigorous than the standard Rodinal. But that doesn’t matter as it’s all about calibration.

In my next post I will review my ‘personal time ‘ for HP5/Rodinal/Portfolio. This will also double check my results above and perhaps confirm that 10 minutes is slightly too long.