film reel: full immersion vs partial immersion

Most of us fully immerse our film reels when developing, with agitation every 30 or 60 seconds. However, some processes use the rotation method (JOBO?), keeping reel turning so that the film is exposed to air only for tiny amounts of time.

Assuming the 'rotation method' has a working solution that covers exactly half of the stagnant film reel (when it is turned on its side). Thus, with rotation, half of the time the film will actually be exposed to air (albeit for maybe one or two seconds at a time). My query is this: with a development time of, say 10 minutes, a full 5 of those minutes have the film fully in the working solution and a full 5 of those minutes have the film exposed to air.

Some of you might have tried both and taken accurate notes concerning both methods. Does the time that the film is exposed to air in the rotation method really count, since that time is for only one of two seconds and might not affect the development at all? In other words, does the rotation method demand a longer development time due to the in and out nature of the film into the developer with this method vs the full immersion method?

Please, for sake of this argument, consider 'developer capacity issues' to be irrelevant. Assume that even with the lower quantity of developer with the rotation method, there is still adequate developer capacity. - David Lyga

In my limited experience there is a difference in development time but I'm not sure it has to do with air exposure. Is there enough surface adhesion so that the air is not really a factor?

Development times for rotary are some 20% shorter than intermittent agitation in a tank. This is because of the constant agitation with rotary processing. When the film is up in the air, the emulsion still contains processing chemistry that has soaked into it and this is replenished as the film hits the fluid again. Oxidation rates are of course higher due to the aeration of the chemistry, which can be an issue with some chemicals (notably staining developers).

Hi David,

I don't do 'rotation film development', but as far as I've read and understood the process, I though one had to TAKE OFF 10% of the usual exposure time?

I do know though, that occasionally when using my Nova print processor, I do take the print in and out of the developer quite often sometimes, exposing it to the air, to see how maybe a difficult negs print is processing. These periods could add up to a good percentage of the time that the print should be in the developer, but I have not noticed any difference between one print immersed fully for 100% of the time and one that has been taken in and out through the development time. I've always assumed that the developer remains active in the paper / film emulsion for longer in time, than the period that the paper / film is out of it, ie equalising it all out?

Just thinking about it, doesn't your usual point mirror what most do when using 'inversion development' of film, where the film is in and out of the developer and into the air upon each inversion? Whatever way it's done, I would think that the times would be minimal and not affect the overall result, but I'm willing to be told otherwise.

And another thought... what about 'dip and dunk' processing of film? Are there any time differences to be made for doing this over the 'inversion' method etc?

I hope this is not too long winded of a reply and that it may be of some help and I look forward to reading others comments.

Terry S

OK, this is rather interesting. Koraks seems to be most in tune with what I presumed. The time out of the developer is not sufficient to qualify for NOT being in the developer, thus the 'constant agitation' of the rotary method actually presents a need to DECREASE development time. Interesting and I thought as much before I posted. Tezzasmall seems to corroborate this thinking. But it was a topic that I see rarely addressed and maybe we all will learn other things from this simple query. - David Lyga

No matter what type of tank you have, development is only affected by the developer that is soaked into the emulsion and the thin layer of developer that is immediately adjacent to the emulsion.
That developer does get used up and development byproducts (which impede development) do build up in and around the emulsion, but the combination of agitation and the availability of the rest of the developer in the tank replenishes the used developer with fresh and active new developer and moves those byproducts away, which allows development to continue without pause.
In agitation by rotation systems, the film is still saturated with developer when it is rotating through the air, and development would continue until exhaustion, except that before it reaches exhaustion, that developer is replenished when that segment of the film is rotated further and, as a result, re-immersed in the solution.
The replenishment process that happens when you agitate the film (whatever system you use) controls how much the development activity is affected by exhaustion and build up of byproducts. The choices you make about how and when you agitate affect the total amount of development over a period of time. You need to adjust the combination of those variables to obtain the result you want. Continuous rotary agitation is obviously more extensive and energetic than other systems of agitation, so it has the tendency to speed up development, but there are other factors that also have effects.
As koraks mentions above, rotary agitation adds a fair bit of air to the developer, which because of oxidation can affect its activity in other ways. Oxidation will vary with different developers, and different dilutions of the same developer. For those reasons alone, if you switch between inversion and rotary agitation, there isn't one, single time adjustment that works for all options.

Excellent and detailed post MattKing.

MattKing said:

No matter what type of tank you have, development is only affected by the developer that is soaked into the emulsion and the thin layer of developer that is immediately adjacent to the emulsion.
That developer does get used up and development byproducts (which impede development) do build up in and around the emulsion, but the combination of agitation and the availability of the rest of the developer in the tank replenishes the used developer with fresh and active new developer and moves those byproducts away, which allows development to continue without pause.
In agitation by rotation systems, the film is still saturated with developer when it is rotating through the air, and development would continue until exhaustion, except that before it reaches exhaustion, that developer is replenished when that segment of the film is rotated further and, as a result, re-immersed in the solution.
The replenishment process that happens when you agitate the film (whatever system you use) controls how much the development activity is affected by exhaustion and build up of byproducts. The choices you make about how and when you agitate affect the total amount of development over a period of time. You need to adjust the combination of those variables to obtain the result you want. Continuous rotary agitation is obviously more extensive and energetic than other systems of agitation, so it has the tendency to speed up development, but there are other factors that also have effects.
As koraks mentions above, rotary agitation adds a fair bit of air to the developer, which because of oxidation can affect its activity in other ways. Oxidation will vary with different developers, and different dilutions of the same developer. For those reasons alone, if you switch between inversion and rotary agitation, there isn't one, single time adjustment that works for all options.

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Right, a long way to corroborate what we just discussed, but in a more comprehensive way. The lining of developing clinging to the film is not YET exhausted (or even nearly so) before another plunge into 'new' developer manifests. However, you bring up the possibility of other developers exhausting before others and state (or infer) that one method is not good for all. Here I might mildly disagree, given the fact the the time out of the developer is rather trivial and, thus, universally unimportant. (Many will agree with me here, but others disagreeing are welcome to respond.) Thank you for further delineating this topic. Others, given the surprisingly robust initial impetus of this thread, will elaborate even more. - David Lyga

David Lyga said:

Here I might mildly disagree, given the fact the the time out of the developer is rather trivial and, thus, universally unimportant. (Many will agree with me here, but others disagreeing are welcome to respond.)

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Within certain bounds, yes. Once rotation speed drops too far, the time in the air will be of influence. Jobo processors have a speed of about 30rpm at their low setting (at least my cpe2 does), wich is not low enough to be of influence - even lower speeds, I don't know what happens. The fact that many experience uneven density at certain rotation speeds suggests that fluid dynamics do make a difference, but I think this is mostly due to turbulence and hence locally higher rates of replenishment and not so much due to oxidation of developer.

It isn't the time in the air that affects the development so much. It is the speed and extent of rotation and movement of the fluid that affects it.
I expect that the time in the air combined with the speed of rotation probably does have a significant effect on oxidation.

Yes, I agree. I think you formulated it more clearly than I did.

Gentlemen:

MattKing: I feel that there is more than adequate movement in the solution with rotary to state that development time modification becomes a factor ONLY when the air time is increased greatly (with slow rotation) and NOT by movement of the fluid as you might presume. So I politely disagree that air time is the deciding factor at work here. I rotate by hand and the 360 degrees is achieved about each few seconds. That is slower than the norm but I feel that this does not give ample time for exhaustion troubles.

koraks: "uneven density at certain rotation speeds suggests that fluid dynamics do make a difference"
Well, what does this mean? Does it mean what I want it to mean, in that slower speeds increase air time? However, given my 54 years developing film (back then, 45 cents a roll for 120 B&W Kodak Verichrome Pan) I think that even a rotation rate slower than 30 rpm would NOT present exhaustion problems. Maybe, just maybe, the 'surge' of development is too consistent with auto rotors and presents a problem of UNeven agitation. There are many answers to this query and I am discovering them as I read. However, you will have to excuse me now, as I must leave computer until tomorrow. Thank you. - David Lyga

David Lyga said:

Maybe, just maybe, the 'surge' of development is too consistent with auto rotors and presents a problem of UNeven agitation.

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Local variations between laminar and turbulent flows, I think that is the cause of the longitudinal "cart track" unevenness experienced sometimes with rotary development in Jobo tanks.

In rotary process , the emulsion jelly never is free from the developer until it hits the stop process. The air (oxygen) in the tank is exposing the developer to a great surface area (the developer on the film which is not submerged). This situation should emphasize the need for adequate developer concentrate in the tank to avoid exhaustion from oxidation. This is a point emphasized in every Jobo rotary processing manual.

A five minute pre-rinse of any black and white film works with the developer to produce a negative with manageable contrast and good tonal range, using the manufacturer's recommended 'hand process' (intermittent agitation) times. To pre-rinse, put a quantity of process temperature water in the tank, equal to, or slightly greater than, the amount of developer. Allow this loaded tank to rotate on the processor for five minutes. At the end of that period, pour out the pre-rinse water, and pour in the developer. Pre- Rinse times shorter than five minutes may produce irregular development, and should be avoided.
If you do not want to use a pre-rinse, you will need to determine the appropriate developer time for each specific situation. Rotary agitation affects different film and developer/dilution combinations to differing extents. Some developing times may be essentially the same, while others are significantly shortened or even extended. As a rough guide, try shortening the developer time by about 15%. This could vary by anywhere from about -25% to +10% from the original 'hand process' (intermittent agitation) times. A five minute 'pre-warm' is recommended when foregoing the pre-rinse. This time allows the film, reel(s), and tank to stabilize at the development temperature, before the developing begins.

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There are numerous black and white film developers on the market. Many different dilutions of these developers can be used. You must pay attention to the developer concentration and quantity of that specific dilution you plan to use. A specific area of film (square inches) will require a specific quantity of developer to process the film properly. If you use a more highly diluted developer, test to ensure the quantity of diluted developer used will properly develop your film. Not enough developer could cause underdevelopment. This type of underdevelopment cannot be compensated for by extending the developer time.

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Matt said it pretty much as it is. I have found no significant difference between hand and machine agitation at the same times and temperatures. I think that the fill and empty times of rotary processors is slightly longer, and the exchange of fresh vs exhausted developer as the tank rotates vs full submersion is kind of the balance between the two. Also, the greater agitation in rotary processing vs hand agitation makes up for the time the film is not submerged. In fact, I did an experiment long ago wherein I overfilled the tank on my Jobo and got lower contrast and speed even though there was good agitation. It was lower than a partly full tank.

However, you must add enough solution to an upright Jobo or other tank, such that the film is covered before you turn it on its side.

PE

Photo Engineer said:

However, you must add enough solution to an upright Jobo or other tank, such that the film is covered before you turn it on its side.
PE

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In the case of a Jobo 35mm tank the rotary processing amount is 140ml which is 100ml less than that required(240ml) for full immersion inversion agitation. So wouldn't some of the film be uncovered until you had turned it on its side with rotary agitation? I had always presumed this worked OK because the 3-5 secs that some of the film is completely uncovered does not matter, even when it is C41 film and the total time is only 3 mins 15 secs i.e. the percentage time is too small to make any difference.

While most "agencies" suggest that you cut rotary processing time for B&W film by up to 20% this is by no means universally true based on articles in Unblinkingeye and in J Tinsley's book on rotary processing where for certain Ilford films and certain Ilford developers the time is the same for both methods. Tinsley believed this to be the result of pre-soaking the film when he rotary processed B&W but not doing so when using inversion agitation.

Equally strangely or maybe more so, the times for agitation and rotary processing for C41 would seem to be the same even if both use a pre-wash routine for warming the film up to 38C degrees.

pentaxuser

I cannot remember the fill amounts and the coverage OTOMH so I cannot answer except to say that I ran my experiment with 2 rolls on 2 reels and filled it to cover the reels IIRC. As for times, I use the exact times for the films with 8 seconds fill and drain included in the time meaning that I start my clock as I start pouring.

I've found, in general, I need to reduce development time about 15% over intermittent agitation in a hand tank given same film, developer, etc. I use a CPP-2 with lift and in 20+ years of use I've never had uneven development on anything from 35mm to 8x10. I run the tanks/drums at Jobo's recommended speeds, except with using Pyrocat-HD which I run on the slowest speed. Never had any issues with this staining developer, either.

Someone on another thread mentioned the strange fact that whether it is inversion agitation or rotary agitation, both processes involve a pre-soak to bring the film up to operating temperature so no difference there and yet despite the common consensus, endorsed by Ilford that rotary agitation for B&W films generally needs up to 20% less time than inversion, the same does not apparently apply to C41.

I may be doing a correspondent(s) in that other thread a disservice but I cannot recall anyone giving a reason for this. It might be that there is no difference because the film is in fact covered by "sticky" developer for the slightly longer period which occurs when the tank is inverted compared to the very rapid rotation of the film through the inversion i.e. the developer "sticks" to the film long enough so that inversion becomes the same as rotation in terms of complete coverage. However if that explains why C41 inversion still only requires 3 mins 15 secs as does rotation, then doesn't the same reasoning mean that inversion and rotation should be the same for B&W film?

What might explain why this isn't the case is if the C41 developer "sticks" to the surface of the film in a way that none of the B&W developers do, so for B&W film with inversion the surface loses developer contact time which it does not lose in the more rapid rotation method but even with the Ilford method of inversion which is constant inversion for 10 secs per minute all of the film is still "washed" with developer pretty constantly.

The truth is out there but it may be more complicated than we thought in the conventional inversion v rotation scenario. If anyone has an argument that reconciles the above difference between B&W and C41 then please tell us.

pentaxuser

I'm not sure if C41 developed in tank inversions will give the same gamma as rotary processing. I also doubt that many of the people who develop it using periodic inversions would notice the difference, which would be most apparent if the negatives were printed on RA4 - most of the color film is scanned these days and limited reductions of gamma are not necessarily an issue in that scenario.

Remember that color emulsions are many many times thicker than B&W emulsions. There are sometimes over 9 of them. Pre-wetting helps them develop more evenly. This is not as evident in B&W. Also, there is the high temperature to consider.

PE

Kodak has published times for each method (XTOL). Same with C-41. Small tank, deep tank, rotary etc. Be careful following older instructions for Jobo published by 3rd parties. The E6 1st developer time, from an old Jobo publication calls for 7'30" instead of 6'30" for "Fuji films" . I found the standard 6'30" published by Kodak, Tetenal and Fuji to work well.

Kodak doesn't recommend reuse of chemistry used in rotary processing. Makes sense from an oxidation standpoint.

The film emulsion is saturated with solution, and swollen, especially in very warm color solutions. I don't think the brief exposure to the warm, moist air in the drum would have much effect.
Best Regards Mike

So we maybe have now one potential reason why inversion of C41 might be equal in outcome to rotary, namely the C41 developer is much thicker than B&W developers so might result in it effectively sticking to the film for long enough while inverting the tank to continue acting on the surface as effectively as is the case with continuous rotary motion? In other words some of the extra agitation created by continuous rotary motion compared to the "standstill effect" of maybe 15 secs each time for inversion is, in effect, redundant thus the two systems remain equal in their development effect. In this reasoning I have made an assumption that when PE uses the word "thicker" the thickness does confer more stickiness and activity on the film surface but that is me interpreting his word "thicker" . I might be wrong to do this.

The counter argument is the one put forward by koraks, namely it does make a difference to use inversion for C41 and it manifests itself in lower gamma so a C41 developed by inversion is of a lower contrast?. As he says, this can be corrected for if the process is hybrid so doesn't show up. However if there are those using C41 inversion and RA4 printing then you might expect them to post about a lack of contrast in their prints- a kind of slightly washed out /desaturated effect, if you will . If this is the case then I cannot recall such a theme being mentioned but there may be too few "inverters and RA4 printers" for this to show up.

The other explanation might be that the gamma is measurably lower by means of a "measuring machine" but still not low enough to be seen except by a direct comparison of two identical RA4 prints of identical scenes in the true sense identical i.e. same scene, light, camera, film etc

Until we were to see such a comparison then no definite conclusions as to the difference between C41 inversion and rotation may be possible

Is this a reasonable conclusion?

Thanks

pentaxuser

When PE mentioned thicker, he was referring to the emulsion of the film, not the developer. C41 developer has virtually the same viscosity as any other water-based developer (which, effectively, is every developer I've ever come across either IRL or in theory).

koraks said:

When PE mentioned thicker, he was referring to the emulsion of the film, not the developer. C41 developer has virtually the same viscosity as any other water-based developer (which, effectively, is every developer I've ever come across either IRL or in theory).

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Thanks for that. You are quite right. I hadn't noticed he was referring to thicker emulsions or had become too fixated on C41 developer being of a different viscosity from B&W developers. This leaves us with your suggestion. It sounds good to me so the key question is: Does the difference in rotary v inversion really result in a noticeable difference in gamma and if so, why do none of the inversion processes say: as the inversion process results in less active agitation use an extra X number of seconds. I suppose we may be dealing with a process ( inversion ) that is a home enthusiasts one driven by lack of rotary equipment but you would think that in the early days of colour neg processing when money was tight Kodak would have devoted long enough to have checked out what the difference was between the two processes and suggested what to do.

Maybe Kodak and other colour neg film makers never considered the cash-strapped home processor having to use inversion C41 to be a worthwhile market to address, so chose to ignore it?

pentaxuser