Agitation Question

[IanBarber]

When processing black and white film in a paterson tank, does agitation build up contrast in just the high values or does it also build up contrast in the mid-tones.

[koraks]

I would say more the higher up you get on the curve, as the effect should be most noticeable where the developer exhausts the quickest. However, with normal agitation schemes of a few turns every minute or every 30 seconds, I think not a lot of depletion actually occurs anywhere, so I'd guess that the issue is mostly relevant for reduced agitation schemes.

[stawastawa]

related question, if some one has curves comparing agitation schemes (with all else equal) Id be curious to see.

[chassis]

The general idea is that agitation preferentially builds density in the highlights. Lack of agitation lessens this, and the idea is that shadows and mid tones receive preferential development. Or it can be considered that, with little or no agitation, highlights receive less development than they otherwise would. Lots available to read online on this topic. I didn't run across and testing or data. I changed to semi-stand development with a more dilute developer a few years ago and it was, for me, a significant step forward in my darkroom results.

An undesirable phenomenon of greatly reduced agitation is bromine drag. These are visual marks indicating uneven development due to insufficient agitation. Not to be confused with surge marks. There are examples on this site showing bromine drag. The Queensboro Bridge image on my Flickr site has some bromine drag effects. They can be interesting but generally not desired.

[N Dhananjay]

The purpose of agitation is to replace exhausted developer and bring fresh developer to the developing silver halide particles. Since developer exhaustion is a function of the amount of development (which is itself a function of exposure), exhaustion happens more quickly in the highlights. So, if you reduce development, development in the highlights can reduce while development in the shadows and midtones continue. Reduce agitation even further and maybe development in the highlights and midtones reduce while the shadows continue to develop. So you can get a shouldering of the characteristic curve at various points on the curve depending on how much you reduce agitation.

As already mentioned, there are other side effects of reduced agitation. You can get bromide drag (usually bad) and adjacency effects (usually good as it increases the perception of sharpness). Adjacency effects happen at the border of two tones when the fresher developer from the less exposed side and the more used developer for the more exposed side diffuse through the emulsion across these areas. It results in the edge of the high exposure area getting a little more development than the rest of the high exposure area and the edge of the low exposure area developing a little less than the rest of the low exposure area. So at the edge of these two areas, you get this added contrast.

Having said all of this, it feels like the available modern films respond more grudgingly to this development technique. You often seem to need fairly extreme techniques (such as stand agitation or minimal agitation). I also have an individual preference for getting my negative as close to a straight line as possible because I prefer manipulations at the print stage. In general, I think losing contrast in some area of the curve is easy to do but putting in more contrast is more difficult.

Cheers, DJ

[stawastawa]

... I also have an individual preference for getting my negative as close to a straight line as possible because I prefer manipulations at the print stage. In general, I think losing contrast in some area of the curve is easy to do but putting in more contrast is more difficult.

DJ, does this mean you have a standard development? or did you have to adjust your agitation to straighten your curve? if so how?

[Bruce Watson]

related question, if some one has curves comparing agitation schemes (with all else equal) Id be curious to see.

"All else being equal" is bloody difficult to do. Requires a well equipped laboratory. Like they had at Kodak. I'm thinking your best bet for this would be Grant Haist's (Kodak researcher) two volume tome Modern Photographic Processing. He covered the effects of agitation rather extensively IIRC.

Most university research libraries will have a copy.

[IanBarber]

Am I right in thinking that in a situation where you have strong light, reducing agitation with a dilute developer may control those areas whilst at the same time help to increase shadow areas.

[chassis]

Ian, yes. Additionally the old adage still applies - expose for the shadows. Infrequent agitation and dilute developer will not improve shadow density, if it is not there in the first place.

[Tobias Key]

I don't think agitation is the best tool for contrast control. Too little agitation increases the risk of uneven development or bromide drag, so you always run the risk of solving one problem only to introduce another one. Much better to use exposure to make sure you have decent shadow areas and just cut development time if you have highlights that are too dense. Times are always consistent between users too whereas agitation isn't. Two inversions might be gentle or strong, or 10 seconds inversion might mean invert twice or five times.

[Steve Sherman]

Am I right in thinking that in a situation where you have strong light, reducing agitation with a dilute developer may control those areas whilst at the same time help to increase shadow areas.

In theory your statement is correct IMHO. What real world wisdom tells me is that the shadows will benefit but only if the delicate balance allows enough time for the shadows to fully develop. That is essentially why so many photographers must double their ISO when using manufacturer's suggested development times, times and dilution being too strong for shadows to fully develop because of the short time, hence the need for more bottom end exposure and reduced development to produce negatives more in keeping with most people's taste.

[Steve Sherman]

Ian, yes. Additionally the old adage still applies - expose for the shadows. Infrequent agitation and dilute developer will not improve shadow density, if it is not there in the first place.

I would slightly change the wording to shadow densities will fully develop when the dilution, agitation frequency and development time most exploit mid tone densities while preventing the highlights to rise to "where they ordinarily would" given how high on the straight line or shoulder given the field relationship was elative to the mid tones

[Steve Sherman]

I don't think agitation is the best tool for contrast control. Too little agitation increases the risk of uneven development or bromide drag, so you always run the risk of solving one problem only to introduce another one. Much better to use exposure to make sure you have decent shadow areas and just cut development time if you have highlights that are too dense. Times are always consistent between users too whereas agitation isn't. Two inversions might be gentle or strong, or 10 seconds inversion might mean invert twice or five times.

I regularly control N - 4 and N - 5 through dilution and agitation frequency and length of agitation, virtually never do I have bromide drag or uneven development, even toned skies don't show signs of extremely dilute or infrequent agitation. The key I found is very early on in the perfection of Semi-Stand development was that the initial agitation was paramount to the success, the initial agitation sequence must be fairly aggressive, not violent yet not gentle either for the Process I use to process film in this manner. To truly realize Adjacency Effects the developer must exhaust at the boundaries of dissimilar tonalities. This is what DJ refers to and Edward Weston used to refer to as a Mackie Line, of course EW had the benefit of thick emulsion films back then and the effect was every bit as dramatic back then. The effects nowadays can be just as powerful under exacting conditions but the balance of the initial agitation, dilution, intermittent agitation, and frequency of agitation are the keys. The formula that works for my 5x7 film will not work for 4x5 film as there is less sq. inches of film and therefore exhaustion rates will certainly differ. If you have further interest in this topic take a look at a free video I just released on the topic here: https://www.youtube.com/watch?v=Rfx22wbksaA

Cheers, SS

[HiHoSilver]

Ian, 'nothing useful to add, but I'm following w/ lots of interest. 'Glad you posted the question.

[IanBarber]

Sp picking up on what people are saying... In an opposite scenario (Flat lighting very low subject brightness range) using a semi-stand type development with little agitation is going to be of no use what so ever, in fact, it may produce even flatter looking negatives ?

[Jim Noel]

When processing black and white film in a paterson tank, does agitation build up contrast in just the high values or does it also build up contrast in the mid-tones.

Contrast has to do with the difference in value between low values and high values. Agitation increases density in the high values, and to a much lesser extent in the low values.

[Doremus Scudder]

Am I right in thinking that in a situation where you have strong light, reducing agitation with a dilute developer may control those areas whilst at the same time help to increase shadow areas.

Ian,

Changing agitation to control contrast is neither controllable nor, often, enough. The time-tested (pun intended) method for adjusting contrast when developing is to shorten your developing time (e.g., the Zone System, et al.). You compensate for the slight loss in film speed caused by reduced development time by exposing more in the first place (because you metered the scene and knew it needed reduced development and, of course, you've tested all this).

What you are referring to is a form of compensation. As DJ explained beautifully, it changes the characteristic curve of the film. This is not a bad thing if that is what you are working for (i.e., lots more separation in the lows and mid-tones than in the highlights), but it has a look all its own. Plus, compensation doesn't work with every developer.

BTW, "strong light" doesn't necessarily mean high contrast and vice-versa.

So, in a situation where you want to get a scene with extreme contrast to print well and still retain a lot of separation in the highlights, you likely would not want a compensating scheme. If the opposite were true, then yes, a compensation regime might be the best choice.

FWIW, reduced agitation by itself does not necessarily make for "low-contrast" negatives. It needs to be coupled with the right developer, overall developing time and agitation intervals.

Best,

Doremus

[Pere Casals]

When processing black and white film in a paterson tank, does agitation build up contrast in just the high values or does it also build up contrast in the mid-tones.


Agitation will favor the more density building just in the high values, in general it will favor much less building density in the midtones because there is much less developer exhaustion there.

It also depends on developer concentration. Stock Xtol 1:3 is exhausted inside emulsion before than Xtol stock. So agitation pattern will have more effect with well diluted developers.

Just get an Stouffer wedge, make contact copies on film, and develop each with different agitation and developer dilution. You'll see with your eyes the real effect with your film and process.

With some situations it can be the risk of bromide streaks with low agitation. Sheets developed in trays have little risk because then gravity doesn't help bromide drag.

Also there is the posibility of divided (2 bath) developers, that plays with component exhaustion to limit excessive contrast.

Let me also mention the "Adjacency Effects". This has some importance in small formats or for big enlargements. With less agitation you get an slightly sharper look.
Still fresh Developer of not light exposed areas help development in the frontier with exposed areas (and the reverse).

Finally, in not done yet, take a look at "Film Development Cookbook"

https://www.amazon.com/gp/offer-listing/0240802772/ref=tmm_pap_new_olp_sr?ie=UTF8&condition=new&qid=&sr=


And / Or Darkroom Cookbook

http://www.ssnpstudents.com/wp/wp-content/uploads/2015/01/Focal-Press-The-Darkroom-Cookbook.pdf


Regards !

[Pere Casals]

Ian,

FWIW, reduced agitation by itself does not necessarily make for "low-contrast" negatives. It needs to be coupled with the right developer, overall developing time and agitation intervals.

Best,

Doremus

Very well pointed... you nailed the issue: lower contrast negatives are obtained with less development, reduced agitation just "can" limit highlights development, giving more shoulder to film.


We have to say "can" because a concentrated deverloper is not prone to controlled exhaustion...

[Michael R]

Sp picking up on what people are saying... In an opposite scenario (Flat lighting very low subject brightness range) using a semi-stand type development with little agitation is going to be of no use what so ever, in fact, it may produce even flatter looking negatives ?

When it comes to total negative contrast, reduced agitation techniques only result in compression/compensation when paired with compensating-type developers. Very few general purpose developers fall into this category. For example, two developers commonly used with reduced agitation (dilute HC-110, dilute Rodinal) don't really work this way. The results are often people seeing what they want to see.

That said, when it works, greatly reduced agitation can potentially be useful even with low contrast subjects IF the developer promotes edge effects. In that case the photographer may choose to use a reduced agitation process and print on high contrast paper. The resulting exaggerated edge effects (sometimes called "micro contrast") can enhance the perception of contrast and sharpness (ie the same effect as using an unsharp mask). Whether or not this is desirable is completely subjective. It should be noted, however, depending on the emulsion and developer, edge effects may or may not be increased by reducing agitation. This is complex.

It also goes without saying one must watch carefully for uneven/mottled development when using semi stand techniques, and develop a process which avoids these pitfalls to the greatest extent possible. Many of the examples I see look terrible.

[N Dhananjay]

I like my negative to be developed as close to a straight line as I can. It is rare for me to deal with photographs where the highlights are small and fall out of the scale of the paper. Usually, if the highlights of the negative falls out of the range of the paper, I prefer to rely on dodging and burning. My reason for this is that the local contrast stays even through as much of the scale as possible (i.e., the toe and shoulder are minimized as much as possible). Its just the way I like my prints to look. Keep in mind that I contact print.

Getting this to wrk has been difficult. HD curve shape appear to be primarily an emulsion characteristic. I've never had much luck with changing the curve shape in any significant way, although from various reports, it sounds as though older film such as Super XX were probably more responsive in this respect. The TMax 400 was mostly all straight line, but most modern films were pretty good - their Dmax was so high that the shoulder was a non-issue and you could choose based on toe shape and other things you cared about. I did some tests a long time back with different agitation schemes and read the densities and did not see much evidence of changes in curve shape - it was just the slope of the curve which changed. So, I concluded that there was not much to be gained by this because if the look of the final print is a combination of two slopes (the slope of the film and paper curves), lowering one while increasing the other (N- film development with higher contrast paper) would be a wash (barring any minor changes due to the inevitable changes in the toe and shoulder). I can see that some prints might be impossible to dodge and burn (although dodge burn masks used with a pin registration system can be pretty accurate) but for the most part, I decided it was simply not much use for my work. However, to a certain extent, I am exaggerating. Its not straight line HD curves per se - developing to a somewhat high contrast and using contact printing processes (with a paper capable of holding a longer range of negative densities) minimizes the area of the toe and shoulder. The problem I usually have is the fact that I cannot get to higher contrast negatives (N+ developing) since modern films appear to have lower gamma infinities.

I hope the clarifies the meaning of my earlier post. Cheers, DJ

[N Dhananjay]

I also wanted to add (as pointed out by Steve and Doremus) that any curve shape due to agitation requires careful massaging - it will only work if you restrain highlights while allowing shadows to develop to completion. Usually this requires considerable increase in exposure to support the shadows and fairly extreme reduction in agitation. My guess is that some of the creative control has been 'removed'/reduced by manufacturers to ensure repeatable results for people with less than perfect process control - it ensures that most people get repeatable results.

Also note that most people appear to use these techniques to control subject brightness range (SBR) whereas they are actually techniques to control local contrast - increasing local contrast in the shadows while reducing it in the highlights - what I have come to regard as a robbing Peter to pay Paul game since it appears to complicate my life unnecessarily. If you have a long SBR, you can do an N- development but that will result in lower contrast throughout the scale - in effect you steal a bit of local contrast through the entire scale and use it to accommodate some more tones at one end of the scale. I have never had much luck getting satisfactory (for the way I want my prints to look) results this way. I prefer trying to use filtration to control contrast where I can and with judicious dodging and burning.

This is not a technical issue but an aesthetic one. Any medium has a limited range and cannot accommodate the huge SBRs we encounter in the real world - painters have it worse, their material can probably accommodate only a range of about 1.5 D compared to the 2 D and higher ranges photographic material can accommodate. They have come up with clever ways around this - playing sophisticated games with local contrast, adjacency effects and the like. Those are lessons we might be well served by studying.

Cheers, DJ

[Steve Sherman]

Sp picking up on what people are saying... In an opposite scenario (Flat lighting very low subject brightness range) using a semi-stand type development with little agitation is going to be of no use what so ever, in fact, it may produce even flatter looking negatives ?
Actually, and respectfully submitted the reasoning you suggest is exactly opposite of what I find to be the benefits of any Minimal Agitation forms of processing film. I am going to expand on my reasoning in a general post right now at the end of what has currently been offered by those participating in this thread.

[Steve Sherman]

There has been a lot of opinion and reasoning offered in this thread and I believe where the thread has gotten off track and is confusing to those possibly not as versed in Minimal Agitation forms of development is in terminology.

Reduced Agitation we all know effects the highlights first and to the greatest degree. So it is natural to assume that Semi-Stand is a form of reduced agitation, no debate. What gets left out of that "general" reference is True Semi-Stand or Extreme Minimal Agitation forms of development go well beyond just reducing the densities of the most highly exposed areas of the negative, S-S and EMA forms of development are designed so a delicate balance of Dilution, Agitation Infrequency and Length of time in the Development stage rely on the Developer exhausting at some point during the "standing" portion of the development time. Only when Developer exhausts can Adjacency Effects happen, they happen in varying degrees dependent on the ratio of strength ( how dilute ) length of time between Agitation cycles which are usually only 10-20 seconds and how often this developer exhaustion can happen during the total processing time. Once Adjacency Effects happen the Lower and Mid Tone densities take on an exaggerated separation or some would say the "Impression of higher Acutance" There in lies the exact reason why with very flat lighting and a low contrast scene the very best way to expand the final contrast appearance in the print is to exaggerate the Mid Tone separation and resulting contrast. So, while the amount of tonalities actually sitting on the straight line or slope of the films curve may not make up much difference from the lowest to highest, S-S and EMA forms of film development when the developer is by design allowed to exhaust the actual straight line or slope of the H&D curve is altered, the slope becomes steeper and it most clearly seen in the Low to Mid Tone contrast.

So in summation, if the very low contrast scene's lowest values are placed on the very beginning part of the straight line of the film's curve and the actual highest measured density of the scene is controlled to fall within the end processes capability to render tone in the highlights the Mid Tones are exaggerated to the point where the print becomes a full range print with deep shadows and well controlled highlights and the Mid Tone relationships are a result of Adjacency Effects that are a direct result of Developer exhaustion. Each scene's actual contrast will dictate how to process the film but ultimately the Highlight must stay in a printable range for your final medium, whether it be Silver or Pt. / Pd. As I stated in an earlier entry, I just released a 20 minute video that will explain in detail with side by side comparisons of 7x17" negatives, one tray agitated the other Semi-Stand processed for 45 minutes There are scores is not 100's of photographers talking about Semi-Stand or EMA forms of development, very rarely do I hear any reference whatsoever to the single most important part of the technique, that the Developer must exhaust for any Adjacency Effects whatsoever to happen.

I hope this clarification on terminology is helpful.

Steve Sherman

[Pere Casals]

Actually, and respectfully submitted the reasoning you suggest is exactly opposite of what I find to be the benefits of any Minimal Agitation forms of processing film. I am going to expand on my reasoning in a general post right now at the end of what has currently been offered by those participating in this thread.

Hello Steve,


I find very interesting your point of view. You make clear that agitation is a major tool in certain conditions.

162818

162819

I wanted to know how your processing modified images and I took an screenshot and compared histograms, well, IMHO difference is great and non trivial.

We can modify the second image with PS to make it match to the first one. It can be done, but it's difficult to obtain a really perfect match. Also IMHO microcontrast if different.

So now I see minimal agitation as a power tool to obtain nice pure optical prints. I'll add that to my learning program, with CRM/SCIM.


Thanks.

Best Regards

[Steve Sherman]

Hello Steve,


I find very interesting your point of view. You make clear that agitation is a major tool in certain conditions.

162818

162819

I wanted to know how your processing modified images and I took an screenshot and compared histograms, well, IMHO difference is great and non trivial.

We can modify the second image with PS to make it match to the first one. It can be done, but it's difficult to obtain a really perfect match. Also IMHO microcontrast if different.

So now I see minimal agitation as a power tool to obtain nice pure optical prints. I'll add that to my learning program, with CRM/SCIM.


Thanks.

Best Regards

Thank you Pere, I'm not much of a PS guy, I know enough to get my images up to the web but am grateful that even on a computer screen the difference in Mid Tone or Micro Contrast whatever one chooses to call is detectable and has been borne out by your test !

Many thanks, SS

[IanBarber]

Thanks to everyone for their input, much appreciated and informative.

Enjoyed your video Steve about your process

[Steve Sherman]

Thanks to everyone for their input, much appreciated and informative.

Enjoyed your video Steve about your process

Thank you Ian for your kind words, and I will again thank Pere Casals for the Histogram analysis he provided as I believe this provides clear validation for the Minimal Agitation process is in fact a powerful technique and will begin to validate for the Non Believers who still remain. It's my hope that the entire thread has been a reward for all who have participated

Cheers !!