Rodinal dilution question?

[stradibarrius]

When you dilute Rodinal 1+100 or 1+200 is there a minium amount of the Rodinal that needs to be in the tank?

Example if I dilute 1+50 in 500 ml there is 10ml of Rodinal.
If I dilute 1+100 in 500 ml there is only 5ml of Rodinal and obviously if I dilute 1+200 there is only 2.5ml.

Is there a minimum amount of chemistry that needs to be in the tank????

 

[mablo]

5ml Rodinal in a 500ml tank is quite normal if you are developing one roll of film. If I intend to develop two 135 rolls in the same 500ml tank I usually add 1-2ml of Rodinal on top. So my own minimum rule is 3-3,5ml per roll but at least 5ml. I know it's not the absolute minimum but the one I personally use.

Perhaps I should add that I don't use stand development no more. My 1+100 recipe is a 'semi-stand' where I agitate every 3 minutes for 20 minutes in total. Works better with 100 speed or slower films.

 

[burchyk]

I use 5ml per roll often, seems to work well

 

[RobertV]

The official minimum amount of concentrate for Rodinal according original Agfa specs is 10ml. However 5-6ml is the practical minimum for one 135-36 or one 120 roll film. When you lower this concentrate you will depend randomn of the amount Black and White in the negative.

Greetz,

Robert

 

[BetterSense]

I often use 5mL in a 250mL tank.

 

[Jim Noel]

10 ml of concentrate per roll or equivalent.
If you are using less than that you must be consistent to get the same degree of development.

 

[Ian Grant]

I often use 5mL in a 250mL tank.

5ml in 250ml is 1:50.

The problems arise when there's too little developing agent and exhaustion causes compression of the high-lights.

it's not as simple as it first appears because 5 ml in 250ml for a 35mm film is enough to develop a 35mm film with out exhaustion playing much part, 5ml in 500ml is half the strength but one roll of 120 uses the same amount of developing agents to reach a roughly similar density/gamma (contrast).

The actual amount of developing agents used to process an average roll of film is known, it's used to calculate replenishment rates in some developers.

Once a developer begins to exhaust it can be thought of as acting like a two bathe developer, as it's retains it's alkalinity, where the developing agents exhaust in the high-lights but continue in the shadows.

So having the right amount of developing agent present with Rodinal is critical, below the 1+50 dilution, and it was common to use different dilutions for different contrasts.

Ian

 

[stradibarrius]

Ian, you understand exactly why I am asking the question. I am concerned about have enough of the developing agent so that it does not become exhausted. I am shooting some Adox CMS 20 and 1+50 dilution is too much contrast.
I re-read part of another thread where georg16nik says he uses 4 ml in 1200ml of water (1+300) and I saw the results. They were outstanding so I think I will try that.

 

[Ian Grant]

The film in question would benefit from the compensating effects of higher dilution & exhaustion. That's how many low contrast developers work.

So what your reading is along the right lines. I can't add more specifics as films have changes since I used the equivalents in the 1970's

Ian

 

[piu58]

CMS 20 has a very thin emuslion and needs therefore less developer. It may be that 2-3 ml for that film are enough.
It is clear, of course, that developing a document film to normal contrast arises problems. SPUR developer is intended to solve them.

 

[Ian Grant]

CMS 20 has a very thin emuslion and needs therefore less developer. It may be that 2-3 ml for that film are enough.
It is clear, of course, that developing a document film to normal contrast arises problems. SPUR developer is intended to solve them.

Don't confuse thin layer emulsions with low silver content, some have a higher silver content than normal films and others aren't substantially less.

The reason you need less developing agent(s) is you need to deliberately prevent the film developing to it's normal full contrast, and this is done by allowing the developer to exhaust.

Ian