How Do You Preflash?

Discussion in 'Paper Negatives' started by bvy, May 24, 2012.

  1. bvy

    bvy Subscriber

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    Curious for some opinions on preflashing paper. I have Ilford MG RC paper (pearl) that I use in pinhole and other box-type cameras. I have a B600 enlarger fitted with an El Nikkor 50mm lens. I'd like to preflash with a quick burst of light from the enlarger. Is this what others are doing? Do you use a graded filter? If not, what is your approach? Thanks.
     
  2. jovo

    jovo Membership Council Council

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    Using the smallest aperture on your enlarging lens (and a translucent white filter if you have one), expose a strip of enlarging paper as you would a test strip for a print. (do not project an image for flashing). Use 1 second intervals. When you've developed the strip, look for the first change from white to palest gray. Any of the times before that one can be used to flash the paper without it registering a tone by itself.
     
  3. Eric Rose

    Eric Rose Subscriber

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    In front of the mirror :blink: Sorry I just couldn't resist lol.
     
  4. DWThomas

    DWThomas Subscriber

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    I use my enlarger, set up for 6x6 format (because that's how it usually is). The lens is set about 24 inches from the easel and set to f/32. I slip a test strip partly under an easel blade which provides some holding and also a masked reference. I then lay a string of small metal washers along the exposed area of the strip. I expose the whole thing for X, cover one washer with a black cardboard, expose again for X. I then work down the string at exposures of 2X, 4X, etc. That gives exposures of X, 2X, 4X, 8X, 16X; eg., stops. That's a quick way to zero in on the general range. I can then refine to a short series of smaller increments if desired. On my setup, X was 0.2 seconds on Arista.EDU RC Grade #2 paper.

    [​IMG]

    Note that some feel multigrade paper is problematic because of varying contrast versus color. Of course the graded paper is mostly blue sensitive, which still contributes to burned in skies. (And excess contrast seems to be the biggest obstacle with paper negatives.)

    So far, the whole process is still a work in process here. Please note also -- it's good to point the emulsion side toward the pinhole! I managed to miss-load one of three filmholders on WPPD -- and naturally, took two of my three shots with that holder, I learned afterwards. :blink:
     
    Last edited by a moderator: May 24, 2012
  5. henk@apug

    henk@apug Member

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    Some time ago I asked a question about preflashing on MG paper.
    A few weeks ago, I bought a copy of Way Beyond Monochrome II.
    There is a chapter on preflashing explaining it very well.
    Highly recommended book
     
  6. Joe VanCleave

    Joe VanCleave Member

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    I use a type S-11 light bulb, 120vac, standard base, round white globe about the size of a golf ball, in a light-tight enclosure with a ~1/4" aperture. I use it suspended about 30 inches above my work table in the darkroom. This permits me to use preflash exposure times of around 5-10 second range, compatible with my old analog Gralab timer. Being incandescent, the filament has to warm up to get its full spectral response, which it can't adequately do with really short exposure times.

    To calibrate the amount of preflash, I did a series of tests in 2-second increments. I don't use the additive method as most people do with test strips, but rather each test increment gets its own full exposure time; this accounts for filament warmup effects. The test paper is then fully processed as per my standard processing. The shortest exposure time that shows a visible density change is what I use for that paper's default preflash time.

    ~Joe
     
  7. Andrew O'Neill

    Andrew O'Neill Subscriber

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    I just hold a piece of translucent plexi up against the lens, along with a predetermined lens apeture and enlarger height.
     
  8. rjbuzzclick

    rjbuzzclick Member

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    I'm very low tech. I lay my paper on the floor, hold a 4w nightlight bulb up by the ceiling, and switch it on for 1 1/2 - 2 seconds (counting the time in my head). Time is tested with a test strip for each paper type.
     
  9. Newt_on_Swings

    Newt_on_Swings Member

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    I also use a very small covered/frosted night light with a flickable switch. It's at about head height hanging.

    This post reminded me to make myself a decent flashing table, I've been doing it on storage boxes as half my darkroom is storage space :sad:
     
  10. pentaxuser

    pentaxuser Subscriber

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    Of course if you are serious about pre-flashing because you expect to do it reasonably often then you could buy the RH Designs "Flasher"

    A bit like its Analyser Pro, it starts to pay for itself from the first pre-flash and no only in materials but in avoiding frustration by getting things right from the start.


    pentaxuser
     
  11. bvy

    bvy Subscriber

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    Thanks everyone for the responses. I used an approach that combines jovo's and DWThomas' methods -- enlarger at maximum height, stopped all the way down. I placed five pennies over a test strip and exposed in one second intervals.

    I didn't have a translucent white filter, but found some clear translucent material and cut it to size. A one second flash didn't register by itself, but it did bring out shadow detail I hadn't been seeing when I made a test image.

    If I find myself doing this more than occasionally, I'll probably look at Joe's method (always good to hear from Joe) or the gizmo that pentaxuser mentioned...

    Thanks again.
     
  12. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    You can also pre-flash in camera with a bit of white plex/whatever in front of the lens.

    Meter through the 'whatever' and give a white-light exposure xx stops less than metered. This works with pinhole or lensed cameras.

    Flashing for paper negatives is very different than flashing for paper prints. For a print you want to flash to a standard "imperceptible almost-but-not-quite-pure-white." If this is what you want to do because of hidebound tradition then give 2 1/2 stops less than metered.

    However, when pre-flashing paper negatives it is better to flash to a density of 0.2 OD to get you well off the toe and on to the beginning of the straight(ish) bit of the HD curve. For an 0.2 OD flash give an exposure of 1 2/3 stops less. [Obviously not what you would normally want when making paper prints, but not a bad idea if you are making enlarged display transparencies from negatives where shadow detail is no problem but holding highlight detail can be the devil.]

    The above exposure figures are for Ilford MGIV RC. But they hold well enough for other Ilford VC papers. They also assume you have calibrated your system so that a metered exposure of a white wall will result in an 18%/ZV tone.

    You can also post-flash - the order of the two exposures is rather immaterial.
     
    Last edited by a moderator: May 29, 2012
  13. SkipA

    SkipA Member

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    I have a couple dozen sheets of very old (bought in 2004) Ilford Multigrade IV RC Deluxe (MGD.1M Glossy) paper. It's 5x7, and I'm going to expose it in a 5x7 pinhole camera. I'll develop a part of an unexposed sheet tomorrow to see how badly fogged it is. If it is fogged, will it still need to be pre-flashed?

    Also, how should this paper be rated?