Pre-Exposure

Discussion in 'Exposure Discussion' started by chris72, May 22, 2011.

  1. chris72

    chris72 Member

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    I want to ask you if you use this method by Ansel Adams in the book The Negative.
    I have some question regarding for this method.
     
  2. RalphLambrecht

    RalphLambrecht Member

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    What's your question?

    Well, before you ask, there is no reason to use film pre-exposure in combination with variable-contrast papers, but when using fixed-grade papers, it's a valuable technique to add shadow detail to the negative.

    I use a self-made diffusion filter to make a Zone II or III pre-exposure.
     

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  3. Doremus Scudder

    Doremus Scudder Member

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    Ralph,

    Out of curiosity, what about VC papers helps you "dig" for shadow detail as opposed to graded papers? Certainly, detail that is not in the negative can't be printed, so you are talking about very low values in the neg. How does VC paper allow better printing of these? (I use graded papers for the most part and am not an expert in the nuances of split-grade printing, etc.)

    Also, I would think that raising shadow values by pre-exposing B&W film would be inferior to simply adding overall exposure and adjusting development for the highlights, since a pre-exposure, while raising the shadow values somewhat, also decreases contrast in those values (like flashing a print lowers highlight contrast). This, unless for some reason, one was trying to create a negative with less shadow separation and relatively more highlight separation, which seems to me to be the exception. (Of course, with color transparency material, pre-exposure is a very helpful technique.)

    I would think that increased exposure and reduced development or print flashing would produce better results in most cases.

    Best

    Doremus Scudder

    www.DoremusScudder.com
     
  4. ic-racer

    ic-racer Member

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    ??
    The shadows in a print are not in danger of succumbing to paper reciprocity failure.
     
  5. chris72

    chris72 Member

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    The question was how to exposure an what filter is use?
     
  6. ROL

    ROL Member

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    I've never quite figured out the absolute need for pre-exposure, and for the same reasons expressed by Doremus, but I suppose those conditions do exist, and am absolutely certain AA made good use of it. Ralph's consideration of graded papers makes sense – if you are using the (a) zone system and can measure all the light in the composition acccurately, you understand and can apply pre-visualization to the scene, and you really need a "between" grade paper to tie it all together.
     
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  7. Jim Noel

    Jim Noel Member

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    Not True! There is a place for pre-exposure no matter what material you are printing on.
    Example: In a forest with the sun streaming in through the trees from in front. The side of the trees facing you would be in deep shade. If you expose for the trees on Zone III, the highlight areas will be burnt out beyond printing capabilities.
    Pre-expose the film on ZOne II then make exposure as indicated for the overall scene. The bark of the trees will now be dark with detail and the highlights will not be blown out.
     
  8. Bill Burk

    Bill Burk Subscriber

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    Hi Doremus,

    Flashing a print and pre-exposure is effectively the same thing with one major exception. On a print you don't want to see gray in the highlights. A slightly grayed negative can be effectively printed down to cancel out the flash.

    The idea is to bring the shadows up further along the toe, so that what little exposure is available in the shadows can start to add density immediately without having to bring the film up to threshold first.
     
  9. Doremus Scudder

    Doremus Scudder Member

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    Bill,

    I am familiar with the techniques of film pre-exposure and print flashing, I use the latter regularly. Film pre-exposure I have used occasionally.

    In both cases, the pre-exposure (or post-exposure, it really makes no difference), brings the material up to (and with film, even beyond) the threshold exposure. The difference is, with B&W film, this is the shadow area and with paper, the highlights.

    In either of these areas, the extra blanket exposure will reduce the contrast in the less dense areas (again, shadows in film, highlights in prints).

    Think of it arithmetically: 1 (arbitrary) exposure unit brings film up to Zone 1 density. Two units give us Zone II, 4 units Zone III, 8 units Zone IV, etc. Now, if I pre-expose with 1 exposure unit (Zone I density) and then give a normal exposure, my Zone I gets 2 units, my Zone II, 3 units (less than a doubling, hence less separation), Zone III 5 units (again less than a doubling), and so on. It is apparent that the lowest shadow zones have less contrast and separation. (A similar thing happens to highlights when flashing paper, but is less objectionable since the eye sees contrast easier in highlight areas.)

    The problem with pre-exposing film is that most of us are striving for more separation in the shadows, not less. With print this is less of an issue, since it is the highlights which are affected and, as mentioned above, the eye does a better job of separating the highlights than the shadows.

    Jim,
    In your situation, I would control contrast by reducing development, using compensating techniques and/or using SLIMTs to keep the highlights printable, i.e., classic Zone System contractions. I would add the extra exposure needed to place the shadows where I wanted them taking my development scheme into consideration, thus placing the shadow exposures well above the threshold. This would retain more separation and contrast in the shadow areas than pre-exposing the film. As I mentioned earlier, with color transparency material, pre-flashing is a viable tool, giving more exposure to the highlights while reducing highlight contrast somewhat, much like print flashing. For B&W negatives, however, I prefer as much contrast as I can get in the shadows, so I tend to avoid it.

    My original question to Ralph has to do with why VC paper would not benefit from pre-exposing film, but graded paper would. I don't understand the reasoning yet... I'm sure Ralph will illuminate things for me.

    Best,

    Doremus Scudder

    www.DoremusScudder.com
     
  10. ic-racer

    ic-racer Member

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    Ok lets see the curves. Flash + full green compared to full green. Or show that flash on any grade will give a curve that will not overlap any other grade.

    We are talking about pre-exposure of PAPER right??? If not then please ignore...
     
    Last edited by a moderator: May 23, 2011
  11. RalphLambrecht

    RalphLambrecht Member

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    The combination of pre-exposue and VC paper makes little sense, because the reduced shadow contrast of the negative requires a harder grade of paper, which pushes most shadow detail onto very low print values. It makes the whole print too dark. You'll find a detailed description here:

    http://www.waybeyondmonochrome.com/WBM2/TOC_files/PreExposureEd2.pdf
     
  12. Bill Burk

    Bill Burk Subscriber

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    Hi Doremus,
    Right you are with the sums and the "reduced contrast in shadows".
     
  13. Doremus Scudder

    Doremus Scudder Member

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    Ralph,

    Thanks for the reply and the chapter from your book. Very comprehensive treatment and quite generous of you to share with us all.

    I guess you were suggesting that pre-exposure is valid for users of graded paper who do not tailor each negative to their paper with development methods and controls, i.e., for roll film users who can use pre-exposure to decrease overall contrast of a particular negative since graded papers now have a rather limited contrast range.

    For a graded paper and a VC paper set to the same contrast (assuming for sake of comparison that the curves are the same too), however, I still can't see how a print of a pre-exposed negative will be different on the VC than on the graded paper... Both should exhibit the same response.

    Usually, for me, I prefer to sacrifice highlight separation rather than shadow separation, and place and develop accordingly. However, your comments about lens flare in older photographs has got me thinking. I may try some pre-exposure to lift the shadows a bit in some scenes and see how I like it.

    Of course, there's always the burning and dodging dance that we all do when we want maximum local contrast and the neg is just a bit too long for the paper.

    Thanks again,

    Doremus

    www.DoremusScudder.com