Film test: crazy idea?

Discussion in 'B&W: Film, Paper, Chemistry' started by DeanC, Dec 20, 2004.

  1. DeanC

    DeanC Member

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    I've basically got the room I'm using for a darkroom setup. Light block over the windows, a small closet that's fully light tight for film holder loading, no big sink but running water into a small one and a big table to hold trays, and room for a light for Azo and a plate burner for pt/pd. Even got my batch of Pyrocat all mixed up. The only thing I'm missing is an easy way to contact print a step tablet onto film for film tests. I'd like to not run out and buy an enlarger just for that (although I see some really low prices for Omega D5s on Craig's List and eBay) so I'm wondering about this crazy idea I just had...

    Instead of an enlarger with an electronic timer or a lens in a shutter, is there any reason I couldn't take this old Vivitar flash I have from my 35mm days that will let me manually adjust the power output, set it up on a stand, a fixed distance above a contact frame in the light tight closet and use a pop from it to expose? I need to stick a flash meter in front of it to get a good read on how bright it is but as long as I can get it to output a useful amount of light, it should work, right?

    Dean
     
  2. Konical

    Konical Subscriber

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    Good Evening, Dean,

    In theory, it should work. Rather than changing the manual power output, why not just select the lowest (weakest) setting and use multiple pops as you gradually remove something opaque (cardboard) step by step from over the paper. I think it would be easier to rig a weak light bulb overhead instead of using the flash.

    Konical
     
  3. sanking

    sanking Member

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    I believe you could make this work by fooling around with the distance from the flash to the contact printing frame. What I don't know is if the amount of light produced by your flash would provide adquate consistency for your testing purposes.

    My own system for exposing film uses an enlarger controlled by a light integrator, which regulates expousures to an accuracy of about 1/100 of a second. However, if I had to set up another system I would probably trash the enlarger and expose with a very small tungsten bulb, night light or such (filtered with an 80A filter), and placed about 4-6' about the contact printing frame. You would need a digital timer for controlling the exposure, or even better a light integrator such as the Metrolux II. You could also use an Olec or NuArc light integrator of the type used with platemakers in the graphic arts, often available on ebay for very reasonable prices.

    Sandy
     
  4. gainer

    gainer Subscriber

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    One thing to consider is the possibility of short exposure reciprocity misbehavior. The flash duration ought to be more than 1/1000 second, I would think, in order to get realistic results for most sheet film users.
     
  5. Roger Krueger

    Roger Krueger Member

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    Konical's multi-pop idea is the best, although you have to be consistent about the timing of the pops--the light comes on at about 80% charged. Do NOT rely on the partial power markings on a 283. My Sunpaks are reasonably faithful to their partial power settings, but my Vivitars area all over the place.
     
  6. noseoil

    noseoil Member

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    If you use a white wall, step wedge and a sheet of film, can't you just use a camera and film holder? I know it has inherent problems with internal flare, etc. but it seems to me that a white wall, light meter and 5 stops of overexposure from zone V will work, if nothing else is available. This is the method I've used in the past and it is sufficient for a close approximation of film speed and development.