Response to Effect of Rodinal dilutions?

I have been using Calbe R09 (also sold as Fomatol R09, Classic F09), the original Rodinal formula (Calbe is a former Agfa company, formula 9 is the number of Rodinal in the Agfa receipe book), which differs from what Agfa sells as Rodinal today, as my standard developer for about 10 years. Since according to my tests R09 is more versatile and provides superior results in most respects in comparison with Agfa Rodinal I can highly recommend its use. That both products are different can be seen from the fact that Agfa Rodinal needs a restrainer (potassium bromide) whereas R09 is clear working without this. Also there is obviously more p-aminophenol contained in R09, which makes is more expensive to produce (this may be the reason for Agfa having altered the formula). As most readers will already know, the dilution will largely affect the overall contrast. The higher the dilution the more compensating does it work. In low concentrations areas with large amount of exposure will "suck up" more developer than areas with little exposure. If the agitation is right (about 10sec per minute) this will give an excellent compensating effect, since the developer is not replenished. R09 will provide this effect in a significant way in the dilutions 1:100 and 1:200. In 1:40 and higher (1:20) R09 can give quite high contrasts and will not work compensating. Due to the wide achievable contrast range the developer is excellent in adapting to differing contrast situations. On the other hand not every film can be developed in any dilution: High speed films from ISO400 up would simply be too soft and would not have enough contrast in 1:100 dilution, unless extreme contrast ranges have to be recorded as in interior photography. On the other hand low speed films, which tend to be overly contrasty in standard situations, will get an excellent contrast rendition with superior tonal scale. Even Technical Pan can be developed in R09 1:200 or 1:250. For low speed films (Ilford PanF, Agfa APX 25, Efke 25) dilutions of 1:100 and 1:200 are highly recommended. 35mm films up to an ISO speed of 200 should generally be developed in R09 1:100 or higher to minimize grain. Grain gets finer with higher dilutions, probably due to the fact that a modest grain reducing effect occurs through the longer time the agent p-aminophenol can work in the silver halides. Still it is not possible to turn R09 into a true fine grain developer and high speed films will show significant grain especially in 35mm. I cannot recommend to add sodium sulfite to Rodinal to reduce grain (as describe in the British Journal of Photography), since this will adversely affect accutance and working characteristics due to the changing PH. Although the dilutions for R09 and Agfa Rodinal are different and direct comparisons are therefore difficult, R09 generally seems to achieve finer grain. Higher dilution will provide more significant edge effect. Especially in this respect I see differences to Agfa Rodinal. The edge effect of R09 is magnificent and hard to believe if not seen. I do not favour Kodak TMAX 100 due to its very low acutance (one might even call it fuzziness) and mediocre tonal scale, but R09 greatly affects both in a very positive way. The compensating effect of R09 in high dilutions will positively improve highlight contrast and will achieve highlight rendition and separation similar to development in pyro formulas such as PMK, with the positive side effect of being significantly cheaper. Mid tone separation is absoluetly beautiful, especially when the film is silver rich, such as the classic emulsions by Foma, Efke, Forte and Ilford. One last word: The developing times provided by Calbe and other sources should be used with great caution. Often only a developing time for dilution 1:40 is given in the data sheets and a general table how to adjust this when diluting differently is added. The mulitplication factor for 1:100 would be 3x and this is definitly too long. The developing time for my standard film Fomapan T200 is 12 minutes for grade 3 paper and diffusion head, instead of the more than 20 minutes that the table would suggest. Higher dilution inevitably affects film speed. The relatively long developing times suggested by the manufacturer could be based on the assumption that the base contrast (= film speed) could be improved by developing relatively long. My measurements show that this is hardly the case and grain will be affected in a negative way, also contrast when developing too long. Statements about film speed on film boxes are very relative. When I check them with my densitometer I generally find them to be about half of what the manufacturer says (with the exception of Efke, which is very close), which is also a good starting point for R09 1:100. Fomapan T200 has an effective speed in R09 1:100 of ISO 64-80.

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