ill second this. I don’t replenish my C-41 developer, and I process *a lot* of film. I also run control strips, and frankly, mixing up a batch of stock developer, then using that to make working solution with the Flexicolor starter has been absolutely predictable and reliable. I know exactly what it’ll do, and can verify it with the control strip. I suspect a lot of variation that people are seeing is actually down to trying to run with too little developer per roll of film. C-41 is not immune to minimum amount of developer per roll requirements. I used to try to squeeze as much as possible out of the developer, and ran 5 rolls in 600ml of developer... well... that only works sometimes. Depending on the content of those rolls, the resulting contrast developed would vary from run to run and thus introduce color cast and other subtle visual artifacts. If you’re an amateur doing it at home and hand inverting each frame, you probably won’t notice or care, but if you’re running control strips and have a fairly tightly calibrated environment, that happening is your bane... so, I started to back off on the number of rolls per ml of developer to see if that made a difference... and it does, and I can actually measure the difference because it shows up in the control strip. I went from 5 to 4 rolls per 600ml, and it stabilized by a measurable amount, but still bumped around a bit over time, so then I backed off to 3 rolls per 600ml, and it just plain stopped bumping around at all and became rock solid, same amount of contrast in each color channel every time, so now that is my minimum for C-41. 200ml per roll. Kodak recommends 250ml per roll, and that probably is a good idea if you expose heavy, but so far, 200ml seems to be a happy medium for a minimum amount per roll.
for replenished XTOL,
@Old Gregg you might want to up your minimum amount per roll. That variation you’re seeing is probably due to not having enough developer per roll. I noticed the same behavior with XTOL, if I ran 5 rolls in 600ml of developer, I was replacing 350ml of fresh back into the working solution bottle, only giving me 250 ml of the just used developer to pour back into the bottle. I found that this effectively is stepping too hard on the developer. Not only is 120ml of developer per roll not enough for consistent and reliable development no matter the content of the roll (which I can measure with control strips), it throws off the replenishment ratio and will vary the overall activity of your bottle over time. I did the same experiment with my replenished xtol as I did the C-41 and started to back off how many rolls per ml and once again arrived at the same 200ml per roll number where roll to roll and overall activity over time stabilized out to a happy medium. Depending on the size of your working solution bottle, this may be more or less sensitive to the number of rolls or may take more time to manifest itself, but it does manifest eventually. I run a 2Liter bottle, and it only takes 2-3 processing runs to show up with that amount of working solution. I used to run with 1L, and when my processing volume went up, I had real problems with roll to roll consistency. I figured it was due to the size of my working solution. The real problem was actually not enough developer per roll. The 1L bottle just manifested a lot faster.
now that I’m officially switching over to replenished Ilfotec DD, I’m going through that exercise right now. I’ve got a 2L bottle that I’m seasoning as I write this, and I suspect that I’ll arrive at about the volume per roll as before.