B&W Reversal - minimizing grain size

Discussion in 'B&W: Film, Paper, Chemistry' started by amuderick, Jun 29, 2008.

  1. amuderick

    amuderick Member

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    I've read that slides can have finer grain than negatives. Why is this exactly?

    Also, if I am using HC-110 (for example), will dilution B vs. dilution H result in larger/smaller grain? Or, will it make no difference?

    How does development temperature effect grain size?

    Thank you!
     
  2. PHOTOTONE

    PHOTOTONE Member

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    What we see in film grain is grain "clumps", the individual "grains" of developed silver are too small to see in even an enlargement. Various developers have various degrees of silver solvents in them, which dissolve the "edges" of the grain clumps thus making them less visible. Microdol-X is a classic example of a developer that minimizes grain due to its solvent action. It is a known fact that different dilutions of a given stock developer solution can have an effect on grain visibility, because this produces different concentrations of sodium sulfite which acts as a silver solvent in more concentrated solutions.

    The theory that slides have finer grain, I think applies to COLOR slides mainly, as the dye-clouds left forming the image, after the silver is bleached and fixed out are more diffuse than the grain clumps would be if it were a b/w image.
     
  3. pierods

    pierods Member

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  4. Photo Engineer

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    Slides don't have finer grain. Grain is grain, it just appears at different places on the tone scale and is either more or less apparent when viewed.

    A 2 micron grain gives the same grain whether developed by a positive or negative process. Think about it. Imagine a film with exactly 2 micron grains and develop it to either a negative or a positive. Either way, the same size grain is forming the image.

    Of course there are other things entering into this such as sharpness and contrast. But, grain is grain. All else being equal, the grain will be equal.

    PE
     
  5. PHOTOTONE

    PHOTOTONE Member

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    I agree with you PE,.....but wouldn't you agree the choice of developer can affect the visibility of grain, due to the solvent action present in some film developers? This effect (rounding off the edges of the grain clumps) should be equally noticeable in reversal or negative, I would think.
     
  6. Photo Engineer

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    There is another thread on this subject going on right now and I said much of what you just did. Developers can change the equation, but again, all things being equal grain is grain. The dividing point is the fact that you can get solvent effects in reversal processes that you cannot get in negative processes, but then, you can get iodide and bromide effects in negative that is supressed in reversal processing. All things are possible and one must work hard to find the sweet spot. That is why Kodak did so much R&D. Then others mostly copied things. :wink:

    PE
     
  7. amuderick

    amuderick Member

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    All this makes sense. PE, you say the grain is in the film...not grown by the developer. But, different developers create vastly different grain appearances based on whether they contain silver solvents. OK.

    So, back to my original question: will I get a different grain effect using HC-110 dilution B vs. dilution H? Will development temperature (time adjusted) effect the appearance of grain? Will it make a difference that I will notice or care about?
     
  8. Photo Engineer

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    Well, reversal first developers and second developers are not generally like normal negative developers. Among other things, first developers contain high levels of silver halide solvents and are high contrast developers like D-19 or something similar.

    You see, the answer isn't simple. There are kits out there.

    PE
     
  9. Jordan

    Jordan Member

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    Grant Haist's book "Modern Photographic Processing" has a chapter on B&W reversal processing. Right near the beginning of this chapter Haist implies (but doesn't state directly) that B&W positives will show finer grain than negatives made using the same film. The reasoning given is that there is a statistical distribution in grain size (with conventional films, of course) and that larger grains develop first. This grainier negative image is all you get with conventional processing, but in reversal processing, the negative image is bleached away and the remaining, unexposed, smaller silver halide grains are used to form the positive image that you ultimately see.

    "Modern Photographic Processing" dates from the 1970s (and IIRC PE is a friend of Haist's) and more modern methods of emulsion-making (let alone T-grain etc.) may render this argument irrelevant but I think this point of Haist's is interesting.

    The book should be available in most university libraries or good city libraries and I think PE once mentioned that there is a reprint available. It comes in two volumes.
     
  10. Photo Engineer

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    Jordan;

    When you measure RMS granularity (Root Mean Sqare), you use a microdensitometer to read a sweep across each step of a 21 step scale and plot the RMS density values as a function of average density deviation vs Log E. If you draw a negative scale, the peak in RMSG is at the dmin and low toe, but in reversal films it is in the dmax and high shoulder.

    Viewing a negative and a slide of the same subject will give the appearance of more grain in the negative because the average density is lower and the statistical variations are larger. However, once printed, both the positive and the negative will appear equally grainy, with the neg-pos system having the better tone scale.

    The tone scale of the print is the product of the first derivative of each point of the film and the print material. Since a negative is a straight line and the positive is a cubic spline, you are compressing detail when you multiply two cubic spline curves together. This loss of detail gives the illusion of higher sharpness due to higher contrast (on average) and better grain due to the same loss of detail.

    This is why you cannot magnify pos pos motion pictures as much as neg pos prints of negatives. The negatives are simply better.

    You can, however, maneuver the positive to get very good results by manipulating the developers, much more so in the first developer. Silver halide solvents come to mind here as I stated elsewhere.

    You can also bleach the grains down in size, but at loss of some detail as I also noted elsewhere. Fundamentally, IMHO, reversal looks good because it is a lossy system that loses grain and uses contrast to enhance edge effects.

    PE
     
  11. Jordan

    Jordan Member

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    PE, your reasoning makes total sense to me (though I had to read it a couple of times). I am merely reporting what Haist appears to be saying at the beginning of that chapter. His discussion about grain in neg vs. pos makes no reference to printing and my impression is that he is comparing positives and negatives directly read, without printing. Not exactly a practical comparison, but it addresses the OP's question.
     
  12. Photo Engineer

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    Jordan;

    If you compare negs with pos, you do see a grain difference and sharpness difference as stated and Grant and I agreed to that. But if you compare an original pos and pos from neg, then the system diverge as I state. Grant and I debated that during the writing and editing of his book(s). This is a very sticky subject that impinges on product sales and quality that is hard to get across to people due to their preferences and also due to very subjective viewing of images.

    I used to bring the galley proofs of Haist home here right where I'm sitting and edit what we argued over during the daytime hours in Grants office.

    There is no easy answer, or no easy explanation. This is a very complex engineering study that relates to the film and to the process. It is more sticky with B&W where the process is a variable.

    PE
     
  13. CRhymer

    CRhymer Subscriber

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    Hello Ron,

    I am relieved that you clarified this (sort of). It has been smouldering in the back of my mind all day. I remembered Grant's chapter, but don't have it at hand, so I was reluctant to comment and perhaps misquote. It appears this is a bit more complicated than one might think at first reading. B&W reversal seems to be one of those third rails of photography. Although I have done a fair bit of it, I am no expert, and have many regrettables and forgettables to prove it.

    I doubt there are that many people who do a lot of it non-commercially. Perhaps I am wrong. On the other hand, one can get a respectable product without too much effort. Now, back to the collodion lantern slides.

    Cheers,
    Clarence