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  1. #1
    henk@apug's Avatar
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    Preflash multigrade paper

    "Pre-flash can be used at different contrast filtrations depending on the effect required"

    I read this in a book but unfortunately, the "effect required" was not specified.

    So my question is what are the effects of pre-flash at different grades ?

    Thanks !

  2. #2

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    I have never heard about this.
    Do you mean to put a filter at the light source and flash?
    This could have a point. Using a 00 filter you could get tone at lights easily.

  3. #3
    David Brown's Avatar
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  4. #4
    henk@apug's Avatar
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    What I ment is when using an enlarger for preflash, one can preflash the paper
    at different filter grades.

    I was wonedering what the different effects are of preflashing with grade 0 or 2 or 4or...

    I think I will spend a day in the darkroom to find out

  5. #5
    RH Designs's Avatar
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    White light is best for flashing. Flashing through hard filters just increases overall exposure, flashing through soft is much the same as white light. So spend your day making pictures instead of experimenting .
    Regards,
    Richard.

    RH Designs - My Photography

  6. #6
    ic-racer's Avatar
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    Sure, flashing multigrade paper works. I suspect if you lost your "00" filter, or if you want to treat only a portion of the image you might want to do it. But otherwise, its not needed.

  7. #7
    henk@apug's Avatar
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    Quote Originally Posted by RH Designs View Post
    White light is best for flashing. Flashing through hard filters just increases overall exposure, flashing through soft is much the same as white light. So spend your day making pictures instead of experimenting .
    Good advice RH !

    By the way, i really enjoy using your f-stop timer

  8. #8
    Ian Grant's Avatar
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    Quote Originally Posted by henk@apug View Post
    What I ment is when using an enlarger for preflash, one can preflash the paper
    at different filter grades.

    I was wonedering what the different effects are of preflashing with grade 0 or 2 or 4or...

    I think I will spend a day in the darkroom to find out
    Flashing is used to help bring out the detail in the highlights and is often used in combination with a higher paper grade / filtration setting so flashing using a contrast filter is of no benefit ans it'll need to be excessive to make an impact on the highlights.

    Most people do the flashing separately to the exposure often using a second enlarger. Split grade printing would be more beneficial tahn trying to do teh flashing through filtration.

    Ian

  9. #9

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    With VC paper, I think white light or ~grade 2 filter would give pretty much the same effect for the pre-flash exposure. I might consider deviating from that if my main image-forming exposure was going to be done with a very soft or very hard filter though. My reasoning there is, if for example the print was mostly going to be exposed at grade 5, the high contrast (blue sensitive) portion of the emulsion is forming most of the image, so assuming the pre-flash is intended to bring the paper to threshold exposure, I'd be trying to "activate" the blue-sensitive layer with the pre-flash.

  10. #10
    Nicholas Lindan's Avatar
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    In general, flash with the same filter you use for printing.

    Flashing with white light will work as well as anything for medium to low contrast filtration but has no advantage.

    For high contrast filtration you really do need to flash with the printing filter. At the high contrast filtrations the curves of the individual emulsions are moved so they stack directly over eachother. Flashing a high contrast print with white light or a low contrast filter will effect only the green sensitive emulsion - one of the three that add up to make the final image - and the results will be week. If the white light flash exposure is increased in an attempt to get a visual movement in the highlights the result will be overall fog in the green sensitive emulsion.

    If you always flash with the same filtration there will be no problems and no worries.

    It should be noted that all emulsions in VC paper have the same intrinsic contrast.

    See http://www.darkroomautomation.com/su...vcworkings.pdf
    Last edited by Nicholas Lindan; 11-25-2010 at 12:12 PM. Click to view previous post history.
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

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