Continuous vs. intermitant agitation for film

[ghuber480]

I have been involved in our great passtime for nearly 30 years and

have been very anal about my processing for consistancies sake.

Recently, I read a short article on developing film using continuous

agitation. The process began with a water bath then used half of the

chemistry and about a third less time. I have experimented with it

and so far I have liked the results, and the savings. As I have

searched the net I keep finding that it is recommended that

continuous agitation be avoided but the reasons are sketchy at best.

Most of the reasons seem to be a knee-jerk reaction to trying

something different. Professional (machine) processors are

continuous but why is it not recommended for small tanks?

[al_divenuti]

Well, the quick answer to your question is that continuous agitation of tanks by 'manual' means tends to lead to bromide streaking which pretty much ruins your negatives. JOBO rotary processors do prevent this streaking to a large degree.

 

However, there are a couple of notable areaswhere continuous agitation negatively affects image quality:

1) Sharpness. Continuous agitation suppresses the creation of sharpness-enhancing edge effects.

2) Film speed. Continous agitation minimizes development time because the highlights developer quicker than they would otherwise. However, this decrease in development time can also result in diminished shadow detail because the shadows continue to develop (albeit to a steadily decreasing extend) with longer development times.

[ronald_moravec1]

The longer development time with rest cycles gives more speed as the shadows develope longer, but you only gain a little.

 

My stainless tanks are 45 years old and I use them weekly. My Jobo does a great job on color neg, 35 to 4x5, but I will not haul it out to develope a roll of b&w. I will do tmx 4x5 in the jobo expert drum, but tri x goes in a hangar or tray.

 

My nikor tanks never fail even if the power goes out. Keep it simple.

[jimvanson]

George -- this is an interesting subject. I thought I'd gotten it somewhat figured out till John Hicks stepped in with a couple of very thought provoking posts --

 

<a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=006GW2"><b>here</b></a>

 

and

 

 

<a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=001KBr"><b>here</b></a>

 

and

 

<a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=002bb6"><b>here</b></a>.<P>You'll probably notice John refers to an article he wrote that is posted on Ed Buffaloe's site <a href="http://unblinkingeye.com/Articles/Rotary/rotary.html"><b>here</b></a>.<P>Lots to read, lots to think about.

[bruce watson]

Depends on who you believe.

<p>

Many people here believe fervently that continuous agitation prevents the formation of "edge effects" and therefore decreases apparent sharpness. I've never found any actual published scientific research to back this claim up, however. And I've looked.

<p>

The only thing I could find that was creditable is from Henry in his book <i>Controls in Black-And-White Photography.</i> Henry apparently found no connection between agitation technique and the formation of edge effects.

<p>

Sadly, there is little actual science being done in this area anymore, what with Kodak getting as far away from us film users as they can, and Ilford having its troubles. We may never know the actual method of the formation of edge effects.

<p>

For my part, I process 4x5 film in a Jobo 3010 tank on a CPP-2. I get perfectly even development, every sheet now for several thousand sheets. My Tri-X is nice and sharp. If you want consistency, continuous agitation is a good thing.

<p>

I suspect that continuous agitation is not recommended for small tanks for a couple of reasons. First, it would wear you out, and you would be hard pressed to maintain a consistent technique for the entire processing time. Second, intermittent agitation with small tanks works really well such that continuous agitation isn't really needed to establish consistent results.

<p>

But that's just my opinion. Clearly, YMMV.

[lex_jenkins]

Jim, thanks for the references to those comments here from John Hicks, as well as his article on the unblinkingeye.com website.

 

I've been thinking about this topic lately because a relative is taking her first photography class as a high school junior. While she and I were developing some film in my darkroom the other day I discovered that her teacher had told students to use continuous agitation (handheld Paterson tanks).

 

That surprised me because I find that continuous agitation is more demanding in every way and unforgiving of mistakes. It typically reduces the EI for films; shortens development times; and results in blocked highlights even if shadow detail is adequate. (These are generalizations, of course.)

 

Also, there's often less tested data available for continuous agitation.

 

My cousin (I tend to think of her as my niece because of the age difference but being country bumpkins we actually have a big passel of cousins of various degrees of removal and I believe she's actually my third cousin once removed but who the hell cares...) had been complaining that her negatives "weren't coming out right" but all she could show me were some test strips and a partial contact sheet. Other problems aside, they seemed to indicate dense, mushy negatives.

 

So I encouraged her to agitate using only two inversions every 30 seconds for this roll and we'd see how it turned out.

 

As I expected there were some exposure problems, partially due to inexperience and partially due to the difficulty of using the TTL meter on the OM-1 she'd borrowed from me, which has a near full-frame pattern, tho' it's slightly oval shaped and center biased. Also the metering cells in the prism are vulnerable to being affected by stray light entering the eyepiece, misleading the user into underexposure.

 

However the negatives weren't overdeveloped and the frames with full shadow detail didn't suffer from blocked highlights.

 

My personal experience with continuous, handheld agitation is that it's more difficult to determine the appropriate development time, highlights do indeed tend to be blocked and, generally, I don't see much advantage to it. I haven't seen any difference in acutance or compensating effects. Those differences are tied to the choice of developer.

 

However with extremes in agitation intervals I have definitely seen differences in acutance and, especially, compensating effects with certain developers. But not with all developers.

 

Oh, yeh, my cousin's teacher also had the students using a one-minute presoak. Their standard film is HP5+ and I told her that altho' Ilford advises against presoaking she should go ahead and follow her teacher's instructions. Per my usual practice, we didn't presoak the rolls we developed that night (one of nominally exposed HP5+ in HC-110 for her, two of Tri-X at 1250 in Diafine for me) and, as usual, they came out fine.

 

I did, however, explain that some films under some circumstances may benefit from presoaking. For example, APX 100 and Efke R100 generate an impressive amount of liberated dye the moment they come into contact with water.

 

Ilford and Kodak films generally don't show any signs of liberated dye after a plain water presoak so I'm skeptical of that particular benefit. I'm also skeptical of the claimed benefit that it prevents "airbells" (why not just call 'em "bubbles"?), pre-swells the emulsion or removes excess tar and nicotine.

 

But I haven't read any credible reports that normal presoaking (1-5 minutes) causes any harm. And pouring out that lovely aquamarine offal from presoaked Efke R100 is awfully impressive so it at least *feels* like I'm doing something necessary and useful.

[rowland_mowrey]

Guys;

 

If you pour a liquid out of one container and into another, it tends to 'entrain' or capture air. This air forms bubbles which adhere to any surface in the recieving container, such as the sides of the container or film, if there is any present. You can demonstrate this by pouring water into a black film processing drum and observing the small silver bubbles that form on the sides of the drum.

 

If the liquid is developer, then no development takes place until the bubble is dislodged somehow, and this is not easy. It leads to small light spots on film.

 

Presoaking simply wets the surface and when you pour out the water, leaves a preswollen even wet gelatin behind, that has less tendancy to allow the bubbles to stick.

 

As for agitation, continuous agitation can lead to bromide streaking and oxidation of the developing agent, decreasing activity of the developer by oxidation and increasing contrast by increased agitation. These two effects tend to work in opposite directions.

 

I have run agitation series with nitrogen burst, hand agitation, and mixtures of both and observed increased contrast as agitation increased. I have rotated a drum in one constant direction and demonstrated bromide drag. (Remember the EK drum processor for color paper? It was notorious for bromide drag if you did not use the special developer compounded for it.) I have only seen or demonstrated the aerial oxidation by shaking the developer in an air filled container and watching it turn color. I have never personally run experiments to demonstrate its effects. I have run experiments to demonstrate the effects of aerial oxidation on film. It is considerable, but countered by antioxidants such as sulfite in the developer.

 

If agitation is uniform, then bromide drag or streaking takes place from high to low silver density areas. Therefore, it is best to have an excess of developer solution, and to agitate in a random fashion at all times. The more the agitation, the more development and contrast.

 

Ron Mowrey

[lex_jenkins]

Ron, I've also read plenty of claims that *insufficient* agitation can result in bromide drag (among these the older Ilford Manual of Photography).

 

Is it any wonder there's confusion and skepticism out there?

 

As for the benefits of presoaking, respectfully, I'll decline a pig-in-a-poke. When I've read credible reports based on repeated tests and *repeatable* methodology, then I *might* buy it. Or I might not, never having actually seen any benefit in my own darkroom.

 

If presoaking ever served a purpose it was in the days, usually preceded by the phrase "good old", when film manufacturers were presumed to adhere faithfully to the motto: "...let her paint an inch thick, to this favour she must come."

 

Nowadays experts try repeatedly to disabuse us of the notions that modern films are either "thick" or "silver rich".

 

Lacking such qualities I'm unconvinced that the contemporary thin films we're stuck with need more than a few seconds in the soup to swell to their full, bubble-resistant glory.

 

Let me see it in my own darkroom and I will believe.

[chris_waller]

Speaking from the standpoint of twenty years experience of developing in Paterson tanks I have always used intermittent agitation. Intermittent agitation, as Lex states above, gives the low values in the negative time to build up while not adding density in the highlights. I keep agitation to the minimum compatible with avoiding bromide streaking or mottling.

[david l.]

Ron, I'd be very interested in any observations/thoughts that you might have regarding continuous agitation and acutance. I was under the impression that "edge effects" are the result of diffusion within the emulsion, and thus agitation, which is a surface action, would have little or no effect - especially given that modern emulsions are significantly thinner than older ones. My source on this somewhat fuzzy area is work of Strobel et al. I'm primarily interested in the effects on T-Max.

[jimvanson]

I figured John Hicks was an agitator.<P>

I also use the least possible intermittent agitation possible. I do that because I believe it gives the shadows time to catch up. I was dumbfounded when John reported that there is no difference in shadow detail between intermittent and continuous agitation I was stunned.<P>

<a href="http://www.photo.net/bboard/q-and-a-post-reply-form"><b>Here</b></a>

is the post that REALLY got me wondering...

[sandy_king]

"The only thing I could find that was creditable is from Henry in his book Controls in

Black-And-White Photography. Henry apparently found no connection between

agitation technique and the formation of edge effects. "

 

The people I know who have reported increased adjacency effects with minimal

agitation and stand development procedures are using agitation intervals ranging

from three minutes to as much as twenty or thirty minutes, or even longer with stand

development. The tests made by Dr. Henry did not include either stand

development, or for that matter even minimal agitation. What he tested was constant

agitation, and inversion of the tank at 1-minute and 20 second intervals. I quote from

p. 214 of the second edition of Controls in Black and White Photography. "Since the

edge effects occur because of lateral diffusion in the emulsion layer, the degree of

agitation should have no effect on them and Barrows and Wolfe stated that agitation

produced relatively little effect. Schwalberg (471) disagrees, stating that violet

agitation will completely eliminate these edge effects. I cannon agree since identical

results were obtained on my machine mixed with very vigorous agitation, and

inversion of the tank at 1-min intervals, and at 20 second intervals." This is a far cry

from the three minute and longer agitation intevals recommended by those who have

observed and reported a connection between reduced agitation and the creation of

adjacency effects.

 

I would also note that the developer used by Dr. Hendry to make this test was D76, a

high sulphite solvent developer that is not in the class of high definition developers

that give enhanced adjacency effects with reduced agitation, at least not when used

straight or 1:1.

 

Sandy King

[rowland_mowrey]

Sandy has a good point there.

 

In general, agitation involving normal developers involves a bell shaped curve which represents the optimum in agitation in the center with worse at either end. (I'm excluding stand developing from this, and the developers used for it).

 

Bromide can drift downwards during some conditions causing streaks, if agitation is insufficient. It can move opposite to the agitation direction if constant unidirectional agitation is applied. I demonstrated this with the EK drum processor and color paper at one time.

 

Edge effects arise by having the concentration of an inhibitor peak in the center of fine detail causing 'ears' of high and low density to form around this fine detail, thus enhancing the edge. Too much agitation can disperse the inhibitor too rapidly, thereby losing the enhanced edges. Too little can cause smear of the edge, draggged edges and too high of an ear. (remember, this excludes stand developing)

 

Presoaking helps me with my Jobo process. I see nonuniformity in color prints without the prewet. I probably would see it with film, but I don't want to waste any film. I see air bubbles in B&W films processed without the presoak, using SS tanks and Jobo inversion tanks.

 

Lex, try the little experiment I outlined above. You will see the silver bubbles form on the surface of the tank.

 

I have excluded stand development, as I have never done it. I know little about the developers, and don't feel qualified to even comment on it either way. I am a bit suspicious of it, I must admit. It seems inherently 'wrong' to me from a chemical or engineering standpoint, but that means nothing in the face of results. It also may just indicate my lack of study of the subject. I have enough other things to keep me busy. If I ever get around to it, I'll give it a thorough go and then comment on it.

 

If you want more on edge effects, and 'ears' see Mees or Mees and James, or post a note here and I'll try to draw some curves and post them.

 

Ron Mowrey

[paul_hoyt]

Back in college when I had my first and only course in photography, the instructor gave us a demonstration on how to agitate a SS tanks with 120 film. He warned us about over agitation which would cause developer to channel (spin) around the SS reels and over develop the edges of the film. I followed his technique and my negatives were overdeveloped at the edges or under developed in the center. His reaction was I was too aggressive in the agitation.

 

In retrospect, his technique could be described as how to move the tank and make it look like agitation is taking place, but the solution remains stagnant. A week later I read an article in a photography magazine in which the subject was: "Too little agitation can look like too much agitation. Techniques for film development from tanks to tray." I followed their procedure and for the last 40 years I have never had a development problem that could be traced to agitation. I still do not understand why the lack of agitation developed the edges of the film more than the center and I have never continuously agitated film in SS tanks to see if it truly over developed the edges by channeling at the spirals of the SS reels. All I know is continuous agitation by tank inversion for the first minute and intermittent agitation by tank inversion every 30 second until development is complete works for me.

 

Paul

[lex_jenkins]

I've seen the bubbles ("airbells") you're referring to, Ron. I've done tests on scrap film, loaded onto reels, removing the tank lid to examine results. Bubbles are easily dislodged by rapping metal tank/reel systems. Nothing to it.

 

With the plastic Spanish tank/reels that are sorta-Paterson clones, the combination twist-bump agitation dislodges bubbles. There's a doodad at the bottom of the tank designed to cam the reels up and down along with the twisting motion. In my tests that was sufficient to dislodge bubbles.

 

The only time I had a problem with persistent bubbles was when any Photo-Flo residue was left dried on the tank or reels. But that's a whole 'nuther problem.

[rowland_mowrey]

Lex;

 

I agree completely. But some people don't rap their tanks enough and sometimes there is too much air entrained in the developer. I prefer to take the safe road, thats all. I advocate using what works. (see the stop bath thread - I really really want people to use what works.)

 

Al Weber told me that the biggest problems with residual photo flo are at schools. I would suspect that the same is true of air bubbles - either due to photo flo residue, if your observation holds up, or just as a part of the 'learning curve' in photography.

 

I have not had air bubbles since I was a teen. I have had streaks before I started using a prewet. I do bang on my SS tanks and Jobo hand tanks, and I do use random agitation when doing the job manually, but why take a chance?

 

Ron Mowrey

[al_divenuti]

>>I would also note that the developer used by Dr. Hendry to make this test was D76, a high sulphite solvent developer that is not in the class of high definition developers that give enhanced adjacency effects with reduced agitation, at least not when used straight or 1:1.

 

Yes, and Henry also did experiments that that led him to conclude there was no change in accutance in straight Microdol-X vs. Microdol-X 1:3 for Tri-X and Pan-X - results that Zawadski (among others) disagree with and intuitively just seem strange. So I'm not inclined to let R. Henry have the last word on any "photographic control" determining accutance of a negative unless at least one other credible experimentalist agrees.

[d_poinsett]

Isn't bromide drag dependent on agitation pattern/frequency and the developer itself? In other words, aren't some developers more prone than others?

[__jon__]

I use continuous agitation for both 35mm and 4x5. I get no streaking--actually no

problems at all. Just excellent negs. I do a 5 min. wash and subtract 10% from small tank

times. Works beautifully. I think Henry was right.