Uneven negatives

Discussion in 'Film and Processing' started by oliverthompson, May 5, 2021.

  1. Hi all,

    I've been developing my own film for a little over a year now. First results were very positive, the negatives would always be nice and even, good natural colours. Now I seem to be having more and more issues, mainly with 120 film. I seem to always get patches or streaks of uneven colour. 35mm I've managed to sort this for, I just make sure to give a nice hot presoak so it's all evenly wet before developing, and I make sure to go heavy on the agitation. For 120 I've had less luck, no matter how much I agitate (and I've really gone ham on it a couple of times) there are always uneven patches.

    I use a large plastic tub to keep my chemicals and tank consistent temperatures, heated by a sous vide the entire way through, so I'm confident that's not a factor. Age of chemicals doesn't seem to make a difference in the evenness for me so far. Plus I've had some shots professionally scanned and they still come out with unevenness, so I don't think it's my scanning process.

    I've attached some examples below. The only thing I can think of that has changed since I started developing is I've slowly started developing at higher temperatures as I've got more confident. I think I started at 20 or 25 degrees, moved up to 30, now up to 38.5, with timings taken from my kit's manual (digibase c41). I always give the bleach and fix extra time, and I've rebleached/fixed some shots with no changes. My only thought is that with shorter development times there's more chance for unevenness, and longer/colder development means for agitation for inconsistencies to even out.

    I'd be very thankful for any advice. 0-3.jpg 0-4.jpg
  2. I'm not sure image 2 supports one solution to the image 1 problem - insufficient agitation, or letting it stand too long somewhere in the process. Maybe the problem is insufficient amount of fluid, since you say you are agitating a lot. That would be possible for image 2 as well, one side on the bottom, then the other. Good luck, maybe somebody's got a better idea.
  3. It's possible to agitate too much and too little. These samples suggest excessive agitation, leading to longitudinal streaks on the film. It tends to affect denser areas on the film more than lighter areas. The spool is not a dreidel. Three partial turns, back and forth every 15 seconds is ample. Take care when turning the film against the spiral so you don't dislodge it from the grooves. I've always used metal tanks, agitated by inversion - 3x every 15 seconds.

    Too little agitation tends to leave blotches, and halos around denser regions on the negative where the chemicals are locally depleted.

    I suggest you develop at lower temperatures, 20-25 C if possible. Room temperature probably works well if you adjust the times accordingly, and you don't have to heat or cool the solutions. Maintaining 38-40 C is difficult unless you have a thermostatic mixing faucet and stir the water bath continuously. Chemical activity increases exponentially with temperature (qv, Arrhenius' Equation).

    Streaks can also appear if the film is badly underexposed. Even small variations in density are magnified when you scan or print it.
    Last edited: May 6, 2021
  4. Give us a clue! Please explain your agitation technique in more detail. Such as; tank and reels used, amount of solution, pouring and emptying times, etc.
    Hmmm. That there sounds suspicious. 'Hot' isn't an adjective that should be attached to any photographic processing solution. A presoak, if used at all, should be at the intended developer temperature - no more, no less.
    Hot water clinging to the film will provoke quicker development in some areas and not others. Too hot and it may even distort the emulsion.

    The amount of air-space in the tank is important too. Too little, or no airspace will greatly impede inversion agitation. It's air bubbling past the film during inversion that does the work of shifting stale developer from the film surface, to be replaced with fresh.

    Ignore almost all Youtube videos demonstrating processing technique. Nearly every one that I've viewed has been made by some idiot child with no knowledge or experience!
    murray_kelly likes this.
  5. Is this going to be another 'drive-by' posting I wonder?
  6. Thank you all for the suggestions! I'll try them out on my next development, I've got a roll of 35 on the go right now so it could be a week or so before I get to see if these work for 35mm. I'm going to try a slower/colder development, that's the only thing I've changed since I started developing.

    I have a patterson tank that claims 500ml is enough for 120, but I'm a bit worried that isn't enough. Perhaps I should just make a full litre and then just use enough of it to ensure the film is well covered each time? I can only really buy kits in 1l or 500ml so it'll be one of the two.

    I also noticed a lot of people are agitating every 15 seconds, but I've only been doing it every 30 seconds (as per my kit's instructions). Perhaps if I switched from 3 sharp inversions every 30 seconds to 2 every 20 seconds?
  7. For some people, 100F/38C qualify as hot.

    When I first started doing E6, it was in a darkroom where the hot water faucet had 100F water,
    so I had a little immersion heater to warm up a bowl of water. I could then pour some into
    the water bath to put the tank in, and also little plastic containers with lids, like for food
    storage, to warm up the chemicals.

    But if the OP means over 100F/38C, then I agree.
  8. I usually use the water from my heating bath, it's a very steady 38C, I have an immersion heater which is constantly circulating the water and keeping it up to temp, it rarely deviated more than 0.1 degree so I don't think temperature consistency is the problem
  9. If it states 500ml on the bottom, then that's the amount to use. Overfilling a tank and using inversion agitation is a very bad thing. As previously explained, you need some airspace in the tank for inversion agitation to work properly.

    My SS tank only needs 450ml for a 120 reel. So 500ml sounds right for the slightly bigger Paterson tanks.
    I'm not sure who these 'lot of people' are, or how experienced they are, but every 15 seconds is excessive for hand inversion agitation IME. You're much more likely to get streaking from over agitation than from a modest amount.

    The C-41 process was designed to be used at 38 Celcius. A lower temperature may give rise to colour issues, and may result in inadequate bleach-fixing. The bleach-fixing stage is just as critical as development, with most maker's recommended times being only just adequate with a fresh solution. With multiple use you can easily get under-bleaching that reduces colour saturation and makes scanning difficult.

    Keep the same agitation regimen for the bleach-fix bath as for your developer. Two inversions and a knock of the tank (to dislodge any air bells) every 30 seconds should be more than enough, since it should take about 10 seconds per agitation cycle - with two or three seconds with the tank upside down. That only leaves the film 'standing' for 20 seconds between agitations. Any more frequently and you're basically giving continuous agitation and the processing solution almost never stops sloshing about in the tank!
    Last edited: May 9, 2021

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