BTZS Plotter and Film Testing

I recently had a long conversation on the phone with a photographer who has the BTZS Plotter program and we were talking about film testing. Normally the film test involves exposing 5 sheets/rolls of film under an enlarger light source. The film is placed emulsion up with a 21 step step tablet (just like making a contact print except you are in the dark). The film are processed one for 4', one for 5.5', one for 8' one for 11' and one for 16'.

I recently changed my testing procedure to doing the 4' test first and putting the density readings in the BTZS plotter program. The results for that film test should be about a SBR (subject brightness range) of about 9 (two stops more contrast than normal) or a little bit more. If the results are over or under SBR 9 you can change the dilution of the developer and do the 4' test again. This saves you the trouble of doing all 5 sheets and the results are too contrasty or not enough contrast.

This is now the procedure I use for myself and for photographers whe use our film testing service. It saves the trouble of doing multiple film tests.

An example of this is in the article I did on the new 400 T-Max-2 film for Photo Techniques. The film developer I now use after Phil Davis did an article in Volume 9 Issue 1 & 2 of the D-Max newsletter is Ilford DDX, testing 9 different films and 5 different developers. This developer gives the best film speeds of any film developer I have seen. My normal developing temperature is 75 degrees and the Ilford DDX is diluted 1+9. That seemed to be the best dilution that I found from my BTZS film testing. So when I first tried the new 400 T_Max-2 I did the 4' film test and found the test way to contrasty (about an SBR of 7). So I increased the dilution to 1+12 and it worked fine. Please see the article in Photo Techniques.

This test was done in a Jobo 3010 film drum and in the Jobo I use a 5' presoak (water) before the developer. What is interesting is that I did the same test with Ilford DDX in the BTZS tubes at a dilution and it was fine at the dilution of 1+9. There is no presoak when using the BTZS film tubes (see the video on youtube.com).

I did not expect to see such a large difference in the tests and the dilution of the developer for the same film when doing a presoak or not doing a presoak.

Hope this helps and saves some time and film when testing.

Fred Newman

Very informative Fred. I much appreciate your taking the time and effort to post the information provided.

I have ordered the program. Will a 4 min. Test alone give me full benefit when using thet btzs program?

I'll let the expert answer, but I suspect that the reason for the 4 minute test is to establish the "correct" dilution for your developer. One can see if the results at 4 mintues are "correct" at the dilution of developer that you have used. If "yes", then you can use that concentration for the rest of the testing. If "no", then Fred will suggest another developer concentration to use. Another 4 minute developing time test will likely be recommended. If such results are within certain parameters that Fred will explain, then one will then use the new dilution for all of the other developing times. Fred? Again, the reason for the first 4 minute developing test is to avoid having to run all of the other times and then to discover that the results in the BTZS system are not entirely satisfactory. The 4 minute test helps set the dilution for all of the other developing times.

I'll let Fred answer definitively, but I don't believe a 4' test alone will give you full information.

I mean I don't think the idea is to match Fred's 4' test and then adopt the rest of the data from a gold standard family of tests that Fred did.

I think the idea is to get through the trial and error stage one sheet at a time until the results for a 4' test are reasonable. Then do a full set of tests that gives you full personal information.

I know he is trying to save you running 5 sheets and finding out that you messed up and have to run 5 more sheets.

I agree Bill.