Agitation Aggravation...

I wouldn't put it that way. If all other things are equal and the only parameter changed is that you reduced agitation, then you'll get a negative with a lower gamma (contrast index) and lower Dmax. If your image was getting up into the film/developer's shoulder region, and this decrease in agitation dragged the highlights down the response curve away from the shoulder, then you could get some more highlight separation. But increased tonal separation isn't at all the same as "more detail." The detail you had at exposure is the detail you have -- your process can't create detail.

 

Well, there is another effect depending on film and developer. At low agitation, you tend to see more edge effects around developing images. This can be extreme or mild but can lead to enhanced sharpness. On the extreme edge, you get an effect called "bromide drag" in which the image becomes smeared due to bromide released and which is not evenly redistributed by even agitation.

So, there are pros and cons and techniques to master in using "agitation".

PE

 

PE, I've heard this often but I've never found any supporting science in the literature. Of course the massive Haist set is only available at my local university library so spending much time with it is problematic. So... can you give me any pointers to where I might find research into the effects of agitation on the creating of edge effects (that is, I think, the formation of Mackie lines, yes?) I want to learn more about it but can't seem to put my hands on the actual science behind it.

 

That's not what I said. I couldn't say that without knowing what you intended to do with the film. Different printing techniques need different contrast and Dmax. So one person's "muddy" might be another person's "Crystal Clear."

 

This may sound off topic, but I don't thik so.

Young man, lost. Sees elderly stranger with violin case. Thinks "He'll surely know." Says, "Sir, can you tell me how to get to Carnegie Hall?" Old man says "Practise, practise, practise."

 

Sweet !

 

thank you !

john

 

Edge effects and bromide drag depend on film and developer and so I cannot give any specific pointers.

As agitation decreases, edge effects degenerate into drag effects caused by gravity dragging the bromide downward in the developer due to density effects.

Edge effects have been described elsewhere, but basically they decrease density in the center of a dark image and increase density at the edges, with a defined "halo" around the edge. This gives the perception of increased sharpness. Drag simply causes smeared and altered density effects across the area of the image to the extent that you see it. It is usually worse at the sprocket holes on 35mm film.

If you don't see it, then your film/developer combination is likely insensitive to the agitation you have chosen, but if you do, then it is. This is a hard one to judge. I have seen films and papers with huge effects and others with none. It depends on bromide in the developer, ioidide in the film and a variety of other things that really have no meaning here except as related to what you see, and that is more important than the mole% of iodide.

PE

 

So the formation of edge effects depends on more than just agitation. It also depends on the composition of the emulsion, and the composition of the developer, among other things as yet unnamed.

I'm guessing here, but basing my guesses on your comments about iodide in the emulsion and bromide in the developer. Would it be safe to say that edge effects are more likely from older and slower emulsions (less iodide) and by extension older developers? That one will be less likely to see edge effects from more modern films like TMY-2, and modern developers like XTOL?

 

Bruce;

You have it backwards. Today's films are generally higher iodide.

High iodide in the film or developers low in bromiide enhance agitation defects when agitation is too low.

PE

 

We're talking B&W here, yes? The highlight blocking occurs in printing. It's nearly impossible to block highlights on a modern negative film. But making them unprintable -- that's relatively easy.

If you are darkroom printing, the whole of B&W photography is about using the film an an intermediary. It's a tool you use to translate the subject brightness range (SBR) to the density range on film that matches the printing process you are using. If your film's density is too high, it can be difficult to get good tonal separation in the print's highlights -- resulting in what is often called "blocked highlights." If that's the case, developing less is often the cure. There are myriad ways to decrease developing; less agitation is but one.

This is all laid out more or less articulately in the various Zone System books and their derivatives. My favorites of these are from Adams, The Negative, and from Picker, Zone VI Workshop. Adams gives it to you in great detail. Picker's version is perhaps more readable. And there are many other books; all have their partisans.

It all boils down to the old saw: Expose for the shadows and develop for the highlights.

As to your question: "...could developing a specific way produce more detail in the highlights?" Technically, no. The process can't produce more detail than you capture at exposure time. What the process can do is to expand or compress the tonal values that make up that detail. IOW it can give you more or less tonal separation. Detail and tonal separation are not the same thing.

So, proper exposure is crucial as you say. But so is proper development. So you are not far off -- you've about got it.

 

I had a 50/50 chance, but I usually guess wrong. Oy.

So I'm more likely to see this effect in faster films that have more silver iodide for speed, yes? If I wanted to experiment some and see what I can learn, would I be better off with a more traditional film like Tri-X or a more modern film like TMY? And what would you suggest for a developer? This could be fun.

 

Use a dilute developer with little or no solvent effects and no bromide. Use little or no agitation, say stand processing for example and a long development time. You may see light streaks moving downward from dark negative areas due to bromide drag and you may see halos around some fine images.

As for film, I guess I could not guess well. I would think TMY would be more the one to use with say HC110 dilution H or a dilute old style developer.

I used to expose a gray target onto sheet film and process and see the "mirror" image develop below the target due to bromide drag. I also used to watch the formation of light/dark streaks around sprocket holes. There are quite a few examples posted here on APUG.

PE

 

That phrase "agitation defects" is a key for me. Now I understand why I've never had much success researching this -- there's little said about it in the literature. That's because it's considered a defect due to improper agitation techniques. The "cure" is simply proper agitation. This "revelation" is hardly worth the effort of writing and publishing papers in appropriate scientific journals.

IOW it's the users who want to exploit this particular "defect" who are interested in it; the researchers themselves know about it and mostly dismiss it. As it should be.

 

The trouble with trying to photograph clouds is that they are translucent back lit objects

If you have a Spot Meter, try metering the clouds on an overcast day - they are at least 2 or 3 stops brighter than anything on the ground.

Photographing clouds on their own isn't too much of a problem

Photographing a Landscape and trying to get some detail in an overcast sky is a serious challenge - the brightness range can easily be 10 or 11 stops.

Getting it to all fit onto the film isn't too much of a problem (but you need something like HP5/Tri-x - with their long tonal range) - but you can easily just end up with a flat muddy print.

You need to be able to dodge and burn your clouds at the printing stage to get much at all of cloud detail

Martin

 

Martin;

Absolutely apropos of nothing, and way off topic..... When I was a teen, I convinced some cub scouts that my exposure meter was an altimiter for determining the altitude of clouds.

PE

 

Well, I don't know about all, but certainly many. And it should give you a solid knowledge base on which to base future decisions. That is, you'll have a better idea what's going to result from exposure and developing decisions. You'll be able to bend the film to your will (insert hideously evil laugh here)!

FWIW, many find Adams' book(s) a tough read. If it bores you to tears try another book like Picker's. I'm just sayin' it's not supposed to be a punishment.

 

Reading Fred Pickers book is shorter and much more to the point.

Mike

 

Could be called "Zone system for dummies"

Seriously though, Picker, in later years started making some crazy statements/assertions that discredited him in many peoples eyes, a few examples, cold light, fixer heavier than water, never photograph backlit subjects. He was a salesman first, an AA wannabe second.

Mark

 

I just bought his book on Amazon for 1 cents, maybe that is why it is so inexpensive.