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  1. #11

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    Quote Originally Posted by Photo Engineer View Post
    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 Watson
    AchromaticArts.com

  2. #12

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    I realize that the highlights and shadows all depend on what your liking is but I guess what I am wondering now, is what is "highlight blocking?"

    Does that mean if there is a certain amount of detail in the highlights, say Zone 8 or 9, that by not agitating the detail will not be pushed over Zone 10. Essentially not over developing the highlights if you will?

    Ultimately what I guess I am getting at is if you were to take a photo of primarily clouds with a multitude of tonal ranges and details could developing a specific way produce more detail in the highlights? Obviously proper exposure is crucial but am I far off?

    Seems like a very detailed example but I am thinking this application might work for scenes with overcast skies.

    Thanks
    ~mike

  3. #13
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    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

  4. #14

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    Quote Originally Posted by mr. mohaupt View Post
    I realize that the highlights and shadows all depend on what your liking is but I guess what I am wondering now, is what is "highlight blocking?"

    Does that mean if there is a certain amount of detail in the highlights, say Zone 8 or 9, that by not agitating the detail will not be pushed over Zone 10. Essentially not over developing the highlights if you will?

    Ultimately what I guess I am getting at is if you were to take a photo of primarily clouds with a multitude of tonal ranges and details could developing a specific way produce more detail in the highlights? Obviously proper exposure is crucial but am I far off?

    Seems like a very detailed example but I am thinking this application might work for scenes with overcast skies.

    Thanks
    ~mike
    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.
    Bruce Watson
    AchromaticArts.com

  5. #15

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    Quote Originally Posted by Photo Engineer View Post
    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
    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.
    Bruce Watson
    AchromaticArts.com

  6. #16
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    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

  7. #17

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    Quote Originally Posted by Photo Engineer View Post
    High iodide in the film or developers low in bromide enhance agitation defects when agitation is too low.
    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.
    Bruce Watson
    AchromaticArts.com

  8. #18
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    Quote Originally Posted by mr. mohaupt View Post
    I realize that the highlights and shadows all depend on what your liking is but I guess what I am wondering now, is what is "highlight blocking?"

    Does that mean if there is a certain amount of detail in the highlights, say Zone 8 or 9, that by not agitating the detail will not be pushed over Zone 10. Essentially not over developing the highlights if you will?

    Ultimately what I guess I am getting at is if you were to take a photo of primarily clouds with a multitude of tonal ranges and details could developing a specific way produce more detail in the highlights? Obviously proper exposure is crucial but am I far off?

    Seems like a very detailed example but I am thinking this application might work for scenes with overcast skies.

    Thanks
    ~mike
    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

  9. #19
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    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

  10. #20

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    Quote Originally Posted by Bruce Watson View Post

    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.

    So what your are telling me is keep on reading "The Negative" and all of my questions will be answered :-) I am about half way finished.


    Thanks for the great discussion, this is all good stuff.

    ~m

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