So, I wanted to investigate the age-old “use the C41 chemistry in 2 weeks/one month/6 weeks/whatever” otherwise it’ll stop working altogether and/or provide horrible color casts. And also whether my DIY “Jobo CPP2” can provide the proper temperature control and agitation.
Test conditions:
– Pentax ME Super 50mm f1.7
– 2 x 300w halogen video lights, 80cm away-
– 80B correction filter
– various printed color test targets and assorted stuff
– Fuji C200 film, fresh
– all chemistry was constantly kept in the fridge (4C degrees approx.); in PET bottles, tightly capped and all oxygen squeezed out; chemistry was never poured in plastic mugs or such, to prevent oxidation to the best of my abilities
– home development was done using my DIY constant temperature bath with continuous rotation (using old Tetanal and freshly mixed Fuji Xpress)
– reference development was done by a Jobo ATL, using one shot Fuji Xpress chemistry, at a good local lab
Modus operandi:
– exposed brackets from -3 to +3, over and over again
– split the film into three: one was developed in 2/3 year old Tetenal C41 with 16 films already passed through it; one was developed in fresh Fuji C41 Xpress; the other was sent to the proper lab
– scanned using Pentax KP on tungsten backlight in a acrylic glass sandwich
– minor corrections were done in either LR or C1; nothing that I wouldn’t do to any negative
– to see how much color shift wes introduced, I copied (directly, using Ctrl+Shift+C) all settings from the DIY Fuji normal exposure shot to the other two and the other way around(“copied settings” folder); taking into account that NLP has color shifts (perfectly normal when using color curves) with different shot exposures (and they definitely were slightly different, as I was using aperture priority), I feel that there isn’t any real cause for concern regarding color shifts
File names contain the following numbers, for identification:
Tetenal – 483, 481, 485
DIY Fuji Express – 470, 472, 477
Lab development- 456, 458, 463
Link to the JPGs:
http://s.go.ro/9czd9800
I’ve used the extended times, as instructed by Tetenal; by the naked eye, I think I’m safe to say that the Tetenal negatives are sliiiighlty overedeveloped. Maybe because they prefer to be safe then sorry, as the keeping conditions of the chemistry are so varied in the wild. But I guess that with proper conditions, the extended times are a bit too much – at least for the developer, the BLIX definitely got a lot slower in my clip tests.
Conclusions:
1. taking into account the above storage conditions, I can safely say that the Tetenal C41 kit can be used for at least the 16-20 films Tetenal claims, and kept at least 1/2 a year; will do another test at 1.5 years, as I still have that chemistry; my bet is on it still working properly
2. there do seem to be some smaaaaaaalish color shifts; maybe because of the negative to positive conversion, maybe because of the processing; but as we’re mostly scanning negatives, I’m fully confident to say that even the old and weary Tetanal is good enough for rock’n’roll. 🙂