Information on yield can be found in the data sheet (under the heading ‘Usability’). The data sheet is available at
http://www.calbe-fotochemie.com/prod/pdf/R09.pdf
. Even when I enquired with Calbe, they were unable to provide any further details on this.
Development times for various dilutions are listed under extension factors. If one plots the stated values on a graph (X-axis: dilution, Y-axis: extension factor), one obtains the corresponding extension factors for dilutions 1+25 and 1+50 by interpolation. For example, this yields a factor of 1.25 for 1+50 and a factor of 0.63 for the 1+25 dilution. This means that the development times obtained in this way can now be compared with Agfa’s specifications for Rodinal (taking into account any differences in sensitivity).
With Ilford Delta 400, the speeds are the same for both manufacturers, as are the development times for the 1+25 and 1+50 dilutions. It is also known from the literature that the photographic result is indistinguishable. Now everyone can draw their own conclusions.
In my admittedly not very scientific tests with the APX100, I was also unable to detect any differences between the two developers. I used 10 ml of concentrate per film. In my opinion, it really isn’t worth skimping on the concentrate. The risk of non-reproducible results is out of all proportion to the extra cost of the concentrate. Furthermore, it’s very practical to always develop a film in a Jobo 1520 at a 1+50 dilution, whether it’s roll film or 35mm.
Best of luck for the future.
Regards, Otto Beyer!
