can you elaborate? I don't get this one
MikeSeb hasn't visited us for about 3 months Ralph but I think he was saying that the minimum quantity of stock D76 is 250ml to get the best negative So if you use 1+1 you need a tank that holds 500ml ( 250ml stock a plus 250 ml water ) If you uses 1+3 then you need a 1 litre tank
So a normal tank that is for 35 mm film is no good except for undiluted D76 and even a normal 120 tank is no good for 1+3
Ít begs this question in my mind: Why does the development time then increase so dramatically and likewise increase dramatically again for 1+3 if it doesn't take into account using less than the minimum stock of 250ml ?
I had always thought that it was because you used less stock with dilutions so need more time in the diluted stock to get fully developed negatives. The final point is this kind of progressively weaker solution is Stand Development where in the case of Rodinal you have gone from 1+ 25 to 1+100 and times increase to as long as an hour or more. Rodinal of course is an exception but not the only one (HC110 or Ilfotec HC is another ) in that the acceptable dilutions are high so the minimum stock level is quite small
If you always use the same minimum stock of 250ml in the case of D76 but dilute that stock then are you not still ensuring that that film gets developed to the same level as undiluted film so if you follow the 1+1 times with the equivalent of undiluted stock and extra water why don't you get over developed film given the extra time that is recommended for 1+1?
Maybe the fact that you have extra water in with the same amount stock required for the best development of a film means that the film with extra water is subject to a different effect but that whatever that effect is still takes a longer time to change the film into a negative that is properly developed ?
What would happen if you used the same stock required then added the same in water but developed it for the same time as for undiluted time? So to give an example: If the time for HP5+ with only stock is 8 mins then what do the negs look like if you dilute 1+1 but stick with 8 mins? Is the film underdeveloped because the extra water has prevented the full development of the film Logically this has to be the case it seems
If on the other hand you use the 1+1 time of say 14 mins with the same 250ml minimum stock then what do the negs look like? Logically the extra time has allowed the diluted developer to complete its job of fully developing the negative
However if you cut the recommended minimum of 250ml in half to say 125ml then add on an extra 10% to the 1+1 time of 14 mins this compensates but only partially for the reduction in the minimum stock quantity?
Presumably 125ml is not set in stone but further reductions eventually reach a point where no increase in time greater than 10 % will compensate and give acceptable negatives - a kind of a point of no return?
Where that point is will vary with individuals but Matt's example of 125ml might serve as that point and it does still allow a 1+1 dilution in a 250 ml tank and a 1+3 in a 500ml tank for either a 120 or 135 film
My experience with Perceptol as an example is that simply dividing the 1 litre of stock solution by the 4 films that Ilford say can be developed and then stating that the minimum of stock required must be 1 litre divided by 4 so 250ml is the minimum stock gives an amount that is generous to say the least
I wrote to Ilford about using 62.5 ml as the minimum for one 135 film in a 250ml tank and it said in reply that this was a little below what it thought to be safe which was 70ml Let's say that as I was a customer it was prepared to "humour me" to an extent but I find it difficult to believe that if 250 was the absolute minimum it was prepared to go as low as 70. So what might be the safe minimum for any scene using 1+3?
We can each stipulate what this might be according to our feelings but it looks as if 250 ml in Perceptol's case may involve at least some area of unnecessary waste for the user
pentaxuser
Does that cover the subject
