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  1. #1
    htmlguru4242's Avatar
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    Pre-Flashing prints?

    I occasionally run into a situation where my prints have good midtones and shadows, but the highlights lack detail (though the detail is in the negative). I know that in many cases, I could burn those areas in (which is what I normally do), but in some cases, the shapes of the highlights are rather too complex to burn, and the exposure needed is ever - so slight that burning would have to be very quick.

    Is this a case where pre-flashing the paper may be us use? If so, does anyone have suggestions for methods / times? (I'm using Ilford MGIV and Kodak Polycontrast for my paper).

  2. #2
    gr82bart's Avatar
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    Quote Originally Posted by htmlguru4242
    Is this a case where pre-flashing the paper may be us use? If so, does anyone have suggestions for methods / times? (I'm using Ilford MGIV and Kodak Polycontrast for my paper).
    Coming back from the APUG Conference and watching Les do his magic, all I can say is DON'T DO IT. Use post flashing instead. Brings out the details much more.

    Regards, Art.
    Visit my website at www.ArtLiem.com
    or my online portfolios at APUG and ModelMayhem

  3. #3

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    Pre-flashing will raise the paper inertia point, though getting the right amount without risking safelight fog and veiling the highlights takes some doing. About the only time I use pre-flash is when I am doing safelight tests and want to err on the side of caution!

    It is really tedious to do if you only have one enlarger, and you cannot stock pre-flashed paper for very long.

    Other options are split-grading - put the highlights in with a soft grade and the shadows with the hard grade - or local application of warm developer on fibre prints. There is also the print heavy and light bleach approach, but it does not sound like you have enough detail to do this.

    All these methods can get that little bit of tone in fine highlights, but they do have slightly different effects on the mid-tones and shadows.
    I feel, therefore I photograph.

  4. #4
    TheFlyingCamera's Avatar
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    You might try split-grade printing. There is a lot of info out here on APUG on how-to, so I won't repeat it here. The short version is that you make two separate exposures, one at minimum contrast, one at maximum contrast. You vary the length of each exposure based on what you need to accomplish with your highlights and your shadows.

  5. #5
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    I use a little desk lamp with a dimmer wired in plugged into an enlarger timer and hundg on the wall for some distance. It's a very simple procedure to lay a sheet on the table under the lamp and give it a preflash bump before loading it into the easel.

    For what its worth this is the very same technique used in graphic arts predigital while making halftones. They required a preflash to bring up the shadow detail and correct for ink bleed in the printing process. The time was standardised for all shots as it was just to bump the dot formation over the threshold exposure.
    Gary Beasley

  6. #6

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    I'm a pre-flasher...

    Everything I've read (until today) has said that pre and post flashing have the same effect, although I've always thought it must have some however slight differences. never seen them myself as on occasion I have completed my enlarger exposure and think, oops, forgot the pre-flash so I post-flash and stil get the print I was aiming for. But if Les can demonstrate a difference, I'll believe 'ya.

    If you are going to flash the paper, you must test to work out your enlarger/paper combination, so if you use two papers, you need to do two tests to determine the appropiate time for each.

  7. #7

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    It does make a difference if you do before or after the main exposure. Either one will work but each produces a different result. Sometimes it is necessary, or you want a certain look/effect, to do both, but it is tricky to get the balance right. A slight pre-flash to "sensitize" the paper, then an exposure/burn in your highlight area on a low filter (doesn't have to be a 00 or 0...sometimes those are too much), then your main exposure on whatever grade you want the rest to be on, then an additional burn, on that filter you used for your main exposure). Balancing all these takes paying attention to what you are doing, and the results you get from them. Trying different combinations and watching those results, will make you a better printer in the long run. Since the combinations are endless, it is important to notice the changes that happen with each combintation.
    BTW, post flashing can flatten out the internal contrast of your mid and lower value tones, since it will be putting a flatter exposure on thise subtle highlights, so be careful.

    Hope that helps.

  8. #8
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    I just tried flashing for the first time last weekend. I used the RH Designs flasher mounted next to my enlarging lens. It has a nice test strip feature and digital timer. I pre-flashed the top half of the 16 x 20 paper for 32 seconds and dodged the rest while split printing thenegative. Made a big difference in the highlights.

    However, post flashing would make it easier to gauge the desired effect so I will likely do that next time. The flashing device works very well.
    Jerold Harter MD

  9. #9

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    Dear htmlguru4242,

    I keep a piece of frosted glass at the side of the enlarger. If I run into a print that needs pre-flashing, I burn a sheet with an exposure test. I suppose I should invest some time with a known light source. Maybe an old flash with some tape over it.

    Neal Wydra

  10. #10

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    Can anyone explain why post flash is different then pre? Looking for a technical explaination in plain language. The way I understand it the flash exposure adds to the negative exposure to help bring highlight details above the threshold of the paper. Looked at in this simple way it won't matter if it was pre or post.

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