# Developer Ratios ?

Discussion in 'Black and White' started by paul_c|8, Sep 10, 2014.

1. ### paul_c|8

Sorry for asking this and I hope I have been correct for the last 2 years, but I'm after a time for a roll of 35mm Ilford fp4+ that I rated @ 80 and my developer is Rodinal (the original stuff)
Anyways I came across a few times 15 mins same as box speed, 13 mins, 10 mins and 9 mins ?
One of the guys was explaining how 1+50 means 500ml water + 10ml of Developer, now I always thought it was 490ml of water and 10ml developer making up a total of 500ml.
If anyone can recommend a time for my film it was shot indoors quite flat light on a tripod that would be great but also have i been developing correctly for the past 2 years or have i been getting my ratios wrong ?

2. ### nicolas_renon

If dilution is 1+50, in real life it should translate by 10ml of developer + 500ml of water for a grand total of 510ml.

3. ### paul_c|8

So the real world doesn't factor in to the b&w world ?
surly its easier to say yes 1+50 or no it should be 1:50 when developing, ill come back tomorrow hopefully there a proper answer for me

4. ### nicolas_renon

1+50 and 1:50 are not the same to me but I doubt it would make a noticeable difference (2%) on your negatives in the real world...

5. ### alan_marcus|2

Dilution Math:
1 + 50 or 1:50 reads 1 part concentrate to 50 parts solvent (water).
My approach:
First know the final volume. Why not place the film reel in its tank and fill with water to cover. Pour off the water into a measuring vessel.
Let’s work with 1:50 with a final volume of 1000ml.
First add the two parts of the ratio. Thus 50 + 1 = 51.
This is the fractional volume of the concentrate.
Thus the developer volume is 1000/51 (1000 ÷ 51) = 19.6 (why not round to 20) = 20ml
The solvent volume (water) is 1000 – 20 = 980ml

Suppose the ratio is 1:25 with a final volume of 600ml
Then 1 + 25 = 26 (fractional volume of developer)
Thus 600/26 = 23ml of developer
Water = 600 – 26 = 574ml.

How about 500ml total volume dilution ratio 1:50
Then 1 + 50 = 51
500/51 = 9.8 round up to 10ml of developer concentrate
Water = 500 – 10 =490ml

6. ### mendel_leisk

I think it's mostly the language that's tripping us up. As an example, I prefer to describe Kodak HC110 Dilution B as:
1/4 oz concentrate plus water to make 8 oz
The "correct" way to describe it is apparently:
1/4 oz concentrate and 7 3/4 oz water
The latter contains an awkward and self-evident bit of math, that helps no one, confuses many.

7. Posted dilutions, times and temperatures are starting points. You may have to adjust for your preferences, working conditions, etc.
The test for proper development is how the negatives print (or scan). If you are happy with the results from the last two years, then you have been doing it right, whatever ratio you used.

8. ### nicolas_renon

1:50 means 1 part of developer for a total volume of 50 (2% concentration). Said differently, it is 1+49.
1:1 means no dilution, 100% concentration or 1+0.

9. ### paul_c|8

Ok. so I was just looking at The Massive Dev chart app on my phone, as it shows when you look up a recipe it shows 1+50 dilution if anyone has this app click on the 1+50 and it takes you through you to another page
Volume 500ml
Dilution 1+50
Final Mix 500ml = 10 +490ml so who's right and wrong guys ? when the actual app is mixing both of them up.

10. ### chris_waller

Speaking a s a user of Rodinal for 30-odd years, I mix 10 ml of Rodinal to 490 of water to make 500 ml total of developer solution. This, strictly speaking is 1+49 but the difference from 1+50 is so small as to be of absolutely no practical importance.

11. ### paul_c|8

Thanks Chris, Ill stick with my Rodinal 490ml and 10ml of developer.
Just coming across the 1+50 and then being told its different to 1:50 and then seeing the massive dev chart using both on the same thing totally threw me.
I developed my negs today, water temp is currently coming out of the tap at 21c so I went with 10:45mins for my fp4+ @80 iso and they look good and scan good.

12. ### nicolas_renon

If you follow the chemistry notation rules, there is no ambiguity.

13. ### steve m smith

If you follow the chemistry notation rules, there is no ambiguity.​

Until someone tells you to dilute 1:1.

14. ### nicolas_renon

If you know the rules, you know what 1:1 means as well as any other dilution...

15. ### steve m smith

The problem is, there are chemists' rules and normal people's rules!

A chemist sees 1:4 as 1 part in a total of 4 whereas non chemists see 1:4 as a ratio of 1 to 4 to make a total of 5.
The only un-ambiguous way is to use 1+4.

16. ### nicolas_renon

I fully agree with you that 1+4 is clearer but you have to deal with data as they are communicated and be prepared to understand what 1:4 means...

17. ### lex_jenkins

If you Google around for images of Rodinal labels and instructions you'll see that since the early 1900s the manufacturer has changed the labels and nomenclature, but has always advised Rodinal be diluted "one part Rodinal in (or with) 20/50/etc. parts water". Decades ago the label, including on my oldest bottle of Rodinal, was indeed marked 1:20, 1:25, 1:50, 1:100, etc. - which was a departure from the usual chemistry interpretation of the ratio symbol. Later the manufacturer switched to the less ambiguous 1+20, 1+50, etc. But the dilution instructions have always been the same. And at any solution more dilute than 1+20 it's moot - there's hardly any difference in activity.
Interestingly, as early as 1909 Rodinal included instructions for the 1:100 dilution for stand development (actually 1+100, but the earliest labels used the ratio symbol), promising "soft but detailed" results. Presumably they meant soft contrast but high resolution of detail. Nowadays some new film photographers tend to associate Rodinal with high contrast and gritty grain but that's usually a consequence of following the postmodern conceit of underexposing film and extending development. With some normally exposed films extended development in Rodinal will continue to exaggerate grain but not contrast.
There were also instructions for use as a print developer. Over the decades better print developers were introduced and Rodinal became less cost effective as a print developer. I tried it a few times for print processing but the results were no better than the more cost effective print developers from Kodak, Ilford and others.

18. ### ralph_lundvall

From above:
"The problem is, there are chemists' rules and normal people's rules!
A chemist sees 1:4 as 1 part in a total of 4 whereas non chemists see 1:4 as a ratio of 1 to 4 to make a total of 5.
The only un-ambiguous way is to use 1+4."
I cannot find an example where a chemist sees a total of 4 when presented with 1:4. I only find that it is a total of 5 parts. Everything I find (thank you Google) shows that 1:4 is the same as 1+4.
Here's an example of a chemistry view that they are the same:
https://www.shodor.org/unchem/math/r_p/
Can someone provide an example of 1:4 meaning total of 4 parts from a chemist's point of view?

19. ### wm._j._rentenbach

The way I see it, it's one part stock and four parts of water. ......... I'm a photographer not a chemist and I dislike confusion (got enough to think about) so 40 ml stock A, 40 ml stock B and 400 ml water total of 480 ml is the way I calculate it for Pyrocat HD. Works for me.
For D76 one part stock and one part water .... 8 oz stock and 8 oz water. Always works for me.
Bill