Preflashing

Discussion in 'Pinhole Photography' started by bvy, Aug 31, 2009.

  1. bvy

    bvy Subscriber

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    I’m hoping Joe Van Cleave, the prophet of preflashing, will stop by, but anyone who has an opinion or some experience on the matter, I’ll be happy to hear from.

    I’m working with a cylindrical pinhole camera (think Quaker Oats), f/226, using Ilford grade 2 RC paper (satin) and developing in Ilford chemicals (PQ 1 min, water/vinegar 20 sec, rapid fix 1 min). I get mostly good results, except my shadows are often a little (or a lot) lacking in details.

    I’ve read that preflashing the paper is one solution, but I’ve also read of some pretty elaborate schemes. I really don’t want to build anything in terms of a special light or some other contraption – at least not right away. Is there some quick and dirty, MacGyver-style approach to preflashing that I can try just to get a taste of it? If I see that it works for me, then I might look into something more elaborate.

    Thanks!
     
  2. Andrew Moxom

    Andrew Moxom Member

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    It's a trial and error process for flashing paper and is something that you could do with an enlarger with no neg in the carrier. Stop down your lens and make a test print on the paper you are going to use and do like you would do for a regular test print while printing a neg. then process in paper dev and stop/fix as normal and then look for the time when the paper just starts to show a tone/fog. Then back off to the previous expsoure that gave you that tone. you have now pushed the papers response just up to the inertia point. Then you can use as you normally would in your pinhole camera.

    Your mileage may vary, but it's a starting point at least. If you find your resulting work still looks muddy, then continue to back off on the flashing expsoure until you get the tones and density you want.

    Long term, I would invest in a RH designs paper flasher that can be mounted to your enlarger next to the lens stage and flash your paper that way.
     
  3. BetterSense

    BetterSense Member

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    I just put the paper on my enlarger and expose it without the negative carrier installed. I expose it just enough to put a faint amount of tone if you develop the paper right then. This doesn't harm my pictures to have this faint amount of "base fog" present. Preflashing definietly helps tame contrast.

    I wonder what difference you could make if you preflashed with different Multigrade filters in place?
     
  4. bvy

    bvy Subscriber

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    Thanks so far for the responses. No enlarger at the moment unfortunately. I'm only developing paper negatives and scanning (sorry!) film. I will refer back though, as I hope to start making prints, probably next year. Any other ideas?
     
  5. BetterSense

    BetterSense Member

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    My next idea would be to shoot a grey card held in front of the camera (and maybe moved around) for a certain amount of time before making your normal exposure. Say, 3-5 stops less than you judge for your regular exposure.

    I've been thinking about this myself for when I need to be far away from home.
     
  6. RalphLambrecht

    RalphLambrecht Subscriber

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    Photographic paper is not made for daylight exposures and reacts to the 'blue' light with high-contrast. The best way to make paper negatives (I'm a fan) is to use a yellow filter during the exposure and use half-strength paper developer. It will lengthen the exposure and processing time but does wonders to paper-negative shadow detail and make them a breeze to print. attached are some before and after negatives.
     

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  7. SMBooth

    SMBooth Member

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    Regarding the light I used a 15watt lamp on a dimmer turned pretty much all the way down and diffused it through a plastic milkbottle. Cannot remember the time but easy to test. Held it about 600mm above the paper.
     
  8. Joe VanCleave

    Joe VanCleave Member

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    The grade 2 paper that I use (Freestyle's Arista) I usually develop for closer to 2-3 minutes; inadequate development can sometimes cause you to miss shadow details.

    In the past I've rated this paper around EI=3; but doing more controlled development tests this summer revealed that with the developer mixed fresh, and its temperature maintained close to 68f, I found EI=12 to be pretty good. FYI I've used both Neutol WA and Ilford's Universal liquid paper developer; both I dilute around 1+15.

    Regarding the preflashing, my setup uses a type S11 bulb, which is a white frosted round globe, about the size of a golfball, in standard household socket base, built into a soup can housing with a 3mm exit hole; the lamp is suspended about 30 inches above the paper when preflashing. I've found 10 seconds a good preflash time with my light, paper choice, EI rating and developer methodology.

    For your setup, you'd want to get a dim enough light source such that the preflash exposure times can be accurately timed; I time mine by a standard Graylab darkroom timer that doesn't permit sub-1 second exposures, so getting the light intensity low enough to permit exposure times in the 5-10 second range is important for accuracy.

    I know you don't want to build your own light source. You could try a light dimmer to reduce the intensity; but the problem is that this changes the color temperature of the lamp with changes in voltage. You end up chasing your tail with calibration tests using a light dimmer, since the spectal response of the paper is not linear with wavelength, trust me! Spend a bit of time to make a reliable light source, then do some calibration tests to get your prefered preflash time down. I prefer to preflash such that an otherwise unexposed negative, when developed, yields a faint light-gray tone.

    The idea with a paper negative is to fit all of the scene's brightness range onto the limited tones of the paper. So you don't want a paper negative to have the wide contrast range of a finished print; you want the tonal scale compressed, but maintaining detail in both shadows and highlights (ideally; sometimes this isn't possible, in which case you pick which is more important). Then, when you contact print (or scan and tweak in PS), you can extract the scene's full tonal range into the finished print.

    ~Joe
     
  9. bvy

    bvy Subscriber

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    Joe, thanks so much for responding. So you think I might also be underdeveloping? It's something I should experiment with, I suppose. I'll experiment with a "proper" light source for preflashing. I like your ideas.

    Ralph, I'm intrigued by the yellow filter suggestion. Silly question maybe, but do you just hold the filter in front of the pinhole? The results look good.
     
  10. RalphLambrecht

    RalphLambrecht Subscriber

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    For pinhole photography, it's held from underneath on the lens plate by a lump of blue-tack. But I also make paper-negatives with lens-based photography. I rate the filter/paper combo as ASA 3 for MG-IV paper. It gives me a beautiful tonality and easy-to-print negatives.
     
  11. bvy

    bvy Subscriber

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    I'm revisiting some projects I asked questions about earlier...

    Joe, I'd be curious to see your preflashing machine. Tonight, per your recommendation, I bought an S11 bulb and a socket. I had soup for lunch. How do you house this device? Drill a 3mm hole in the bottom of the soup can? If so, how do you enclose the top and make it light tight? I'm sure I could improvise something, but if you have a good way, I'd rather hear it first.

    Also, the bulb I bought is clear, not frosted. Does that matter much? Should the light be more diffused?

    Thanks.
     
  12. Joe VanCleave

    Joe VanCleave Member

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    I use a frosted white bulb, so I can't say for sure regarding the clear one, but I'm certain you can get it to work.

    I have an aperture stop on the bottom of the soup can. I don't have a photo of the setup available, but I'll do my best to describe it.

    The soup can is upside down; the power cord goes through a hole in the top; I use a rubber grommet to keep the metal from chaffing the insulation on the wires.

    The wires are short enough to permit the socket and bulb to hang inside the can without protruding out the open bottom.

    I have an aperture stop covering the bottom, with about a 3mm hole. The hole size isn't important, except you will want to calibrate the size to permit adequately long preflashing times for your process, based on how far above the work surface it is suspended. I hang mine about 30" above the table; this height was chosen only because it's conveniently located to hang off one of the parts of my Beseller 4x5 enlarger. The important thing here is that it's far enough above the table that the light distribution is even; too close to the paper and the center may get more exposure than the corners.

    I'm not certain about ventilation in the can to keep it from overheating; my design uses a plastic flange from a 2" plumbing fixture, that fits inside the can's opening but permits a bit of air to get around the edges. A black paper disc is inside the opening of this flange, with the aperture stop. The insides of the can and the plastic flange are painted black. You could just try a piece of black craft (scrapbooking) paper, taped over the opening in the can with black gaffers or electrical tape for starters, then see if the can heats up too much.

    As for the non-frosted bulb, if you're worried about the small aperture in the light source producing some pinhole imaging artifacts of the bulb's filament, you could perhaps use a small piece of wax paper over the aperture in the can, which should diffuse the light enough.

    Again, it's a simple device; the whole intent is to permit preflash times that are repeatable, by them being sufficiently long (like 5-10 seconds) in duration so as to permit use of a darkroom enlarger timer.

    Good luck, hope to see some results soon.

    ~Joe
     
  13. bvy

    bvy Subscriber

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    Okay, Joe, thanks for checking in. I guess the point is that this isn't rocket science. The idea is to expose the paper uniformly and in a controlled and repeatable manner.

    I might pick up a new bulb -- or just try the wax paper as you suggested.

    Someone else here suggested a yellow filter and showed some pretty impressive with/without results. Do you have any experience with or thoughts on using a yellow filter for exposing paper negatives?
     
  14. Joe VanCleave

    Joe VanCleave Member

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    No, I haven't tried the yellow filter trick, which, as I understand it, permits the use of multigrade paper to gain a more moderate contrast image, the yellow filter removing lots of the blue/UV light that activates the high-contrast portion of the multigrade emulsion. Since I use graded paper, it's much less contrast sensitive to the color of light and hence doesn't need the use of a yellow filter.

    I've found a combination of preflashing, along with controlling contrast by the use of graded paper, seems to deliver a good paper negative tonal range; I'm assuming that using a yellow filter will give one a benefit for MG paper similar to using graded paper (and which others have reported good results); although you might have to increase your exposure times to compensate for the loss of light from the filter, so perhaps graded paper might permit shorter exposure times (but I'm not certain on this last point, a lot depending on what exposure index you rate your paper, and your developer strength, etc.).

    None of this is rocket science, it's more about keeping good notes and figuring out how best to work with the materials. And I'm looking forward to seeing your images.

    ~Joe