Agitation: Intermittent inversions VS continuous rotary

[gabriele turchi]

Hi all,

Stand process aside ,
i would like to ask your opinions regarding agitation methods , more specifically intermittent inversions VS continuous agitation (rotary process ( jobo)) ....(i guess continuous inversions does not quite make sense ..)

i have a jobo and i find very useful but now i was i am wondering if some of you consider agitation done trough inversions superior than rotary-continuous agitation (quantity of chemistry needed aside )...also i would imagine it also depends on which developer used ...

(if inversions would produce superior results i would consider buying a Heiland TAS , so consistency and time saving would be similar to using a Jobo i guess )..

anyway,
if anyone has any opinion about rotary producing somehow not the """""ultimate"""" quality for some sort of reason , please let me know .

thanks

g

[alberto_zh]

The rotation with a jobo as the advantage of the temperature control. The heiland can’t keep a water bath.



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[gabriele turchi]

The rotation with a jobo as the advantage of the temperature control. The heiland can’t keep a water bath.



Sent from my iPhone using Tapatalk

Good point , but honestly for black and white processing I find that not being a determining factor , since processing times usually are under 10 minutes therefore starting the processing at the right temperature should not Drift much (unless the darkroom is tremendously cold / hot )

I am interested about tonality and grain comparing rotary versus intermittent inversions .

Thanks
g

[Pere Casals]

if anyone has any opinion about rotary producing somehow not the """""ultimate"""" quality for some sort of reason , please let me know .

Rotary development produces perfect standard developments.

Rotary has a drawback, it has a fixed agitation pattern, rotating slower delivers the same result than if faster, so for rotary HC-110 developer is popular because adjusting dilution allows for a certain degree of control.

In regular (non rotary) conditions agitating more or less modifies the developing speed, so time should be adjusted depending on agitation frequency/intensity.

But if you develop in tanks or trays then you have interesting effectes with agitation. First with a lower agitation (combined with diluted developer) chem is exhausted earlier (before an agitation happens) in highlight areas that are building density faster, so the effective development in the highlights is lower, so you have a kind of compensating result, and it prevents highlights building excessive density, helping to conserve highlight detail.

Another thing with reduced agitation is edge effects, that can have some importance mostly in smaller formats. With a reduced agitation (from 1 min intervals, IIRC) you have more acute edges between clear and dark areas,

I'd suggest you reading Darkroom Cookbook, it can be found used and cheap, the 1st edition it's very cheap ($8) (IMHO) because it had some erratas, but the erratas are described here: http://anchellworkshops.com/books/errata/fdc_errata.pdf

For small batches tray development it's really interesting, you can use a paper safe to do it in daylight conditions. With trays you waste little chem in one shot if diluting a bit(1:1 xtol, for example), and as the sheet is horizontal you have way lower risk of bromide drags with low agitation patterns.

About temperature control, this is not an issue for BW, it's really easy to get the right temperature accuracy, or even you can adjust time depending on actual temperature by using a graph or table for the correction.

[Bruce Watson]

I am interested about tonality and grain comparing rotary versus intermittent inversions.

Agitation technique has zero effect on film grain, or film grain clumps. This according to Grant Haist, perhaps Kodak's (and the world's) foremost expert on B&W film development. His two volume tome Modern Photographic Processing is the definitive source still.

What agitation changes, if you don't control for it, is density. That is, if you keep the time and temperature the same, continuous agitation usually gives you greater highlight density (and therefore a greater contrast index) than does intermittent agitation. And since density is made from the formation of silver grains and grain clumps (that is, more density is created by more and bigger grain clumps), it can appear that continuous agitation gives you grainier highlights and more contrast. However, if you control development to give you the same contrast index, and therefore the same highlight density (easy to say but darn difficult to do in the lab), you find that graininess is identical from continuous and intermittent agitation. Haist showed it and published it.

As to tonality, that's more baked into the film. Case in point, Dick Dickerson and Silvia Zawadzki, the research chemists who created XTOL for Kodak, developed XTOL for rotary development using a Jobo system in their labs. I doubt they would have done that if continuous agitation created inferior tonality. Just sayin'.

Things that effect tonality in roughly descending order of importance are, film choice, developer choice, exposure (shadow detail), development (highlight detail and contrast index). Temperature can have an effect with certain developers (mostly MQ developers, as hydroquinone's effectiveness changes fairly noticeably with temperature). But agitation technique alone has little effect on tonality IME.

All that said, the most frustrating thing for me in the darkroom was getting a perfectly smooth gradient like an open stretch of cloudless sky. And this is where a Jobo expert drum (a 3010 in my case) and continuous rotary agitation just shines. No matter what else it does, the fact that it is perfectly repeatable and delivers perfectly smooth development results every time makes it my method of choice.

[MichaelPRyan]

I don't think there is a better method than tubes spinning and bobbing in a water bath. BTZS tubes are great for 4x5 and homemade ABS for 5x7. No streaking, no uneven densities. Round and round, back and forth, up and down. The tube spinning and bobbing in the water defeats in its tracks, any type of laminar flow patterns.

[Pere Casals]

But agitation technique alone has little effect on tonality IME.

Bruce, you posted very interesting references, I'll read on what you cite.

I think that you are right in that, in regular developing conditions, agitation alone has a little effect in tonality, but for contrasty scenes agitation can be a major resource. This is specially important (IMHO) with xtol, that has a tendence to blow highlights.

It is for sure that stand development has a clear impact in the result, as highlights are compressed and detail is preserved there.

With stand development we also get higher microcontrast for the same tonality (in the mids-highlights), this is something that I've measured with histograms. Of course reduced agitation is not stand, but by controlling agitation/dilution we can obtain a result that would shift more or less in the direction of the stand development result.

The effect of stand development in microcontrast it's quite easy to recognize in a side by side test targeting the same tonality in both shots. For that we need to shot an scene that has some contrasty textures, then we scan with any image enhancing disabled, then in Ps we select the same region with the texture, that has the same gray level (average density) in both shots, if we plot the histogram from both regions we see that the one from the stand development is way wider, showing that the texture from the stand development has a greater dynamic range.

I'd say that this is the important factor from agitation, at the end tonality can be adjusted in the post process, and in reality tonality comes more from filtering or from film spectral response (ortho!, blue sensitivity, valleys in the spectrum...), but the effect in micro contrast cannot be overlooked...


I agree that with moderate agitation changes alone we'll see little difference, but a low agitation combined with diluted developer for sure it has a remarkable impact with contrasty scenes... the first effect we see is that we don't blow highlights, or we blow it less, with same effective N- contraction.

[Michael Wellman]

Well, I am going to swim against the tide of Jobo. I have used a Jobo for 15 years. It was nice with good results. I also disagree that agitation doesn't have any affect on grain or contrast development. I think there is evidence against that thought. After seeing negatives developed in Minimal Agitation Development I have switched over to it believing it to be superior to continuous agitation. I am at the early stages of this so I can't give you years of experience to base this on only what I have seen that is possible with it. I suggest you check out Steve Sherman and the Power of Process to get a better understanding of what he calls Extreme Minimal Agitation. This is all on the assumption that you are doing B&W. As for temperature control in a 70° room developing at 70° there shouldn't be any concerns for any rapid temp changes. I use the Stearan SP 445 tank in a water bath without any problems. I am also using pyro which I believe gives you much better tonality than of the standard developers.

[Alan9940]

Good point , but honestly for black and white processing I find that not being a determining factor , since processing times usually are under 10 minutes therefore starting the processing at the right temperature should not Drift much (unless the darkroom is tremendously cold / hot )

Not true! My darkroom generally runs at about 80F during the summer months and, if I start development at 70F the temperature will drift upwards by about 3 degrees over 10 mins. This will vary a bit when using stainless tanks vs plastic, but it will go up. I've tested it. And, trust me, a 2 - 3 degree shift in temp will affect the final results.

Also, I agree with Micheal W that agitation style most definitely will affect negative contrast.

[Pere Casals]

I also disagree that agitation doesn't have any affect on grain or contrast development. I think there is evidence against that thought.

Well, about EMA grain, we also have to account the Pyro effect. The stain reduces the grain perception, as part of the density is built by the stain itself.

Regarding contrast, the Pyro stain also have a remarkable effect on multigrade papers, as the stain blocks more the blue light than the green light it works like if we placed a multigrade low contrast filter in the enlarger that is stronger in the highlights, this may require a shift in the multigrade filtering that favors contrast in the shadows, working like a mild SCIM, I'd say.

These effects comes from the stain rather than from the agitation...

seeing negatives developed in Minimal Agitation Development

Time ago Steve sent me some scans of a side by side test he made, targeting same contrast and densitities, same developer but comparing regular tray development vs EMA. Subject was a rough wall with paintings from white to black. I extracted for him local histograms of different Zones, what I saw is that EMA negatives had a noticeable greated DR in the same local area.

I saw it clearly, anyway this is a repeatable test, anybody can make a side by side test of EMA vs regular.

The nice thing is that (IMHO) while stand is a compensating development at the same time it enhances microcontrast, and this is quite amazing effect that combines with the pyro look in the Steve's recipe.

I don't say that this look it's better or worse than the one from a regular development, this is a personal issue, but for sure that there is a difference.

I guess that for wet printing this effect it's difficult to be emulated with the enlarger. For hybrid process Ps is a powerful tool, but anyway also I guess that fit would be difficult to emulate it well with it.