musikbaer
Hello,
What should I expect, or what do I need to bear in mind, if, for example, I prepare the developer (e.g. Adonal) in a Jobo tank at a ratio of ~1:42 (6 ml of concentrate to 254 ml of water)?
Best regards
Urnes
I was tempted to write something sarcastic just now. But that wouldn’t be helpful.
If it’s a developer that you can dilute that much (HC-110), you’ll end up with a perfectly developed film. Every developer has a minimum concentration that you shouldn’t go below, if that’s what you wanted to know.
Regards, Sven.
musikbaer
Usually, people say the dilution should be 1:25 or 1:50; now, 6 ml in the bottle gives a ratio of 1:42, or with 5 ml (which you shouldn’t go below per development), it would be a ratio of 1:52.
I once tried to work this out using digitaltruth photo with a Fomapan 100 and an Ilford FP4+, and arrived at a development time of 7 minutes for the first and 13½ minutes for the second. Can that be right?
The question is, how precise does it need to be, or are these just tolerance values?
Urnes
Do you mean in general, or in relation to a specific developer?
Regardless of the developer, the time intervals are too wide apart. It’s probably too short for the Foma.
landpfarrer
Hello,
I
don’t think the fact that the development times for the films vary so widely means much. After all, they are two different films. With Adonal/Rodinal in particular, the times often vary considerably. For a 1+50 solution, the Foma takes 7 minutes and 15 seconds at 100 ISO and the FP4+ takes 15 minutes at 125 ISO (both figures from Darkroom Solutions; I’ve had better results with their data than with that from digitaltruth). I’m not sure how you arrived at the 1+42 ratio, but both times seem a bit too long to me.
I’m not quite sure what the background to the question is yet. Which Jobo tank would require 260ml? The 1510 needs 250ml. It works well with 5ml + 250ml; although that leaves 5ml ‘too much’ in the tank, it doesn’t matter.
I
Regards, Jörg
musikbaer
Hello Urnes,
I mean this in general terms. I’m trying to understand the relationships between the developer, dilution agent and time.
€
Hello Jörg,
I have a Jobo 1100 here for practice, and I’ve tried to work out the times based on ratios of 1:25 and 1:50. I calculated an average factor based on time and dilution and applied it to the 1:42 dilution; I know you could also use a factor derived from 42/50 (that seemed a bit too simple to me at first ;) ).
Regards
fototiger
Hello,
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Am I right in thinking that you’re interested in some sort of formula or guide showing how dilutions affect development time? For example, 1+25 gives … minutes, 1+26 gives …, 1+27 gives
… and so on. I’m not aware of anything like that existing in this form.
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I mean, developing is a science, but you don’t have to turn it into one. Especially with Rodinal, I like to round off the liquid quantities a bit if it helps me measure it out more accurately. That’s why I often use a bit more liquid overall than I’d need to submerge the reels.
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I’m also wondering whether it’s actually possible to measure out exactly 5 or 6 ml every single time; that alone introduces a degree of uncertainty. The most important thing, therefore, is consistency. Find your own workflow when developing and fine-tune it to suit you. It’s similar with temperatures; you won’t know 100% for certain whether your thermometer is accurate and whether 20°C is actually 20°C. What’s important, however, is that you always use the same thermometer and use it to gradually achieve the desired results.
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For 500ml of Rodinal, I use 500ml of water and 10ml of Rodinal; anything else is too fiddly for me to measure. I’ve also realised that my results improve when the water is around 19.5°C rather than 20°C (as measured on my thermometer).
Renate
There is no formula for calculating development times for different concentrations of developer. Every developer has their own relationship between concentration and development time. The only thing to do is guess and experiment. The simplest approach is to stick to the concentrations tested by the manufacturer.
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Best regards
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Renate
grommi
With Rodinal (Adonal), the processing times are proportional. For example, half the concentration means double the time. This isn’t the case with many other developers.
And no, developing film isn’t a science but a craft.
Florek
With Rodinal (Adonal), the processing times are proportional. For example, half the concentration means double the time. This is not the case with many other developers.
Furthermore, the contrast changes with dilution, which can be used to great effect for control. Adjusting the development time to account for the changed dilution therefore does not necessarily produce an identical negative.
