I have a Paterson Universal Tank for developing film. It's written underneath that for 35mm we need 290ml to fill.
I plan to put in 500ml into it. Simply because it's easier to make the solution.
I see that the tank can hold up to 600ml-700ml.
Will it affect the final result of development if I do so? Or should I strictly follow Paterson instruction 290ml?
Provided your Paterson tank is of type 115 - the one that can take either two 135 or one 120 films - it is the best practice to fill it with 500 ml (or so... can be up to 520 if using Rodinal 1+25 dilution) of developer.
You can load the second reel empty, to ensure uniform cover or your film.
For most developing situations this is merely a convenience issue, but if you plan to do stand development with heavily diluted Rodinal (say 1+100) you could have real problem with 290 ml only (2.9 ml of stock Rodinal is not enough to ensure even development).
Developing film is a combination of chemical processes. These processes utilize an interaction between the film and a chemical dissolved in a solution.
What do you think happens if there is too little of a chemical for the needed reaction? That's simple: the reaction stops.
Just about everything in the film developing process is based on providing the reaction more chemical than is actually needed and controlling for the reaction through time and temperature.
Development: In developing, 99% of developing is done with an abundance of developer chemical and the total development reaction controlled by temperature and time. This is why you make 1+X of your developer and develop at (usually) 20C/68F for Y minutes (whatever your developer tells you).
You need to make enough developer to cover the film, which is a function of volume. Anything extra is there for padding. What you want to avoid is streaky negatives. This can occur when there is too little developer (volume) and it runs down the partially submerged film. The film can become partially submerged through agitation when not enough fluid is used.
So, your Patterson tank says to use a minimum of 290mL - anything you add is extra padding on this. If the math works out easier to make 500mL, then do it. Keep in mind that this is using up more of your developer than necessary, but it doesn't hurt (except maybe your wallet).
Developer Exception to the Rule: When doing stand development with Rodinal, developing the chemical to exhaustion is the goal. One typically uses 1+50 or 1+100 (or even more dilution) and lets the film "soup" in it for an hour (or more). Rodinal recommends using no less than 5mL of developer (I've seen people say less. This is a highly experimental practice). But, keeping in mind that 5mL is used per 35mm roll, then your minimum volume is 500mL and you'll need to use every.last.drop to get results.
Stop Bath: I don't even measure this. Pour from the jug until the tank is full. Return to jug when done.
Fix/PermaWash: Again, the exact volume doesn't matter as the idea is that the chemical has plenty to react. Pour to cover plus a little extra to ensure proper submersion during agitation.
Photo Flow: Yep, same thing here. Although using any more than enough to cover the film is simply wasteful at this step.
Take the top off of the tank, put in the real/reals and fill with water until the top of the real/reals are covered with water.
Pour the the water into a measuring vessel and then read how much liquid it took to cover the real/reals.
Write the amount down for one real and for two reals ( or more if it holds them ) and pin it to your darkroom wall over your sinks.
You may want to round it up to a nice round number ( metric ) for ease of mixing.
Now you can figure out your amount for mixing the different amounts for any number of reals then post those formulas on the wall.
Agitation with Paterson tanks is done by spinning the reel, so it's only necessary to cover the film. Other systems, where agitation may be by inversion or other means, require the tank to be nearly full (some air is required).
The necessary chemical reactions occur based on concentration and time. Having more or less solution in the tank won't affect results, as long as the film is adequately covered. For convenience, it's fine to just fill the tank to capacity.
Using low volumes of low-concentration solutions can result in developer being exhausted prior to the full development of the film. The problem is developer is exhausted and concentration essentially drops to zero midway through development. To avoid this issue, you can use higher concentrations or larger volumes to prevent the concentration from dropping too low. These can be characterized within a recommendation to use a minimum amount of developer, prior to mixing. (Using more developer without increasing volume increases concentration; while using more developer, with the same concentration, increases volume.)
