Flashing Paper

Discussion in 'Enlarging' started by Alex Hawley, Mar 9, 2004.

  1. Alex Hawley

    Alex Hawley Member

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    Something I've been wanting to try is flashing the paper to contract contrast. My idea is to take a small square of transluscent plastic (the type used in lighting fixtures) in the filter drawer of the Beseler. But I have no idea how long to flash for.

    Anyone have any thumbrules or starting advice? I will be using MG paper.

    Second question. Has anyone combined flashing with split contrast exposure?
     
  2. Donald Miller

    Donald Miller Member

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    Alex,

    There are several ways of flashing paper. Some even use a device sold by RH Designs. I simply remove the negative carrier from my enlarger and use the enlarger to flash for a time that I have tested and found to be just below exposure threshold. This will depend on how much light leakage you get out of the enlarger with the carrier removed. I don't have much from the Durst. I don't use any diffusion device at all in my preflash work. Since enlarger bulb wattages vary, it is difficult to tell you what times may or may not work for you. I typically find that at F16 and a grade three filter pack in my Durst at 8X10 enlargement that the preflash time will run about 1.6 seconds on JandC Polywarmtone Classic. Other papers are faster then this paper. I would preflash Oriental for 1.2 seconds.

    Insofar as preflashing and split grade printing, yes it would work...I suppose...even though I haven't done it. I typically preflash at a single contrast grade.
     
  3. Nige

    Nige Subscriber

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    your diffusion material needs to be below the negative if your leaving it in the enlarger. I use a seperate enlarger with no negative in it but still use a diffuser! For me, that equates to 2secs @ f5.6 with the diffusor on Agfa RC!
     
  4. Ka

    Ka Member

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    In what circumstance does one "flash"?

    What are the benefits of flashing?

    What will change or be altered?

    I understand how to do it, just not when I should want/need to do so.

    Thanks,
    Ka
     
  5. Donald Miller

    Donald Miller Member

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    Preflashing of the paper is a technique that allows one to enhance local contrast and still maintain overall contrast within the parameters of the papers properties.

    I have a couple of images posted in the Critique gallery. Both of those images were preflashed. I wanted to enhance local contrast within the rocks to show texture. If I had not preflashed the paper the ocean would have lost all texture. By preflashing I was able to enhance local contrast and maintain texture in the water.
     
  6. Bruce Osgood

    Bruce Osgood Membership Council Council

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    Alex,

    I have dabbled with the flashing concept and MG paper. What I concluded was that with the enlarger lens set 24" above the paper and at f-16 and the lamp (Chromega D II head) at white light, a two second exposure would produce a shade just breaking the surface base white of the paper. You will need to experiment with your own tools but I think you will come out somewhere near my findings.

    When you decide on your flash exposure, make a half-dozen sheets or so and reserve them for use later. Don't make so many that you can't afford to chuck the whole idea later (just my Scottish ancestry talking).

    With a cache of flashed paper it makes no difference what printing technique you use. You are using a 'custom' paper base that will respond to straight printing, split contrast, contact, etc.

    Now, flashing in Texas may be illegal, it is here in NY. Be careful who you flash in front of.
     
  7. kkranis

    kkranis Member

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    I have a simpler method: I use my lighter (zippos or that kind are no good).

    I stand 3m away and lift the lighter on shoulder level. THen I just fire two or three flashes. It works!
     
  8. Bruce Osgood

    Bruce Osgood Membership Council Council

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    OOOOPPPPS, meant Kansas, not Texas.. sorry.
     
  9. gainer

    gainer Subscriber

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    I have an easel densitometer that I use in conjunction with an adjustable light source separate from the enlarger to "while" flash. When I have determined the readings on the easel densitometer for the white and black thresholds for a given exposure time, I adjust the enlarger diaphragm for the shadows and the separate source for the highlight. Both lights are controlled by the enlarger switch, so both are on during the printing exposure, which is why I call it "while" flashing.

    A rather simple light meter should do the trick.
     
  10. lee

    lee Member

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    not Texas.. sorry.


    IN Texas in it legal as long as no one sees it. So in the dark of the darkroom it is perfectly ok.

    lee\c
     
  11. Les McLean

    Les McLean Subscriber

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    Alex,

    A couple of weeks ago I received an email from a fellow apugger asking for advice on paper flashing and I promised to send him a draft of an article I wrote some time ago for a UK based photo mag. I have at last found the time to do this so I will be happy to do the same for you if you would send me your private email address. My email is les.mclean1@btopenworld.com
     
  12. yeahyeah

    yeahyeah Member

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    I have used the flashing method on MG quite a bit recently. Here is my method....

    I raise the enlarger head as high as it will go, set the lens at the smallest aperture then make a test strip to find out the flash time. I used an otherwise unexposed piece of MG paper and used 1 second increments. After developing the paper in the usual way, I use the time where I first see non white. I have flashed both before and after exposing for the main print. I find it a particularly useful tool in printing.
     
  13. Alex Hawley

    Alex Hawley Member

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    Thanks to everyone for all the good tips. This isn't as hard as I was trying to make it. Somewhere down the road, I'll post some results in the Technical Gallery.
     
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  15. Aggie

    Aggie Member

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    Hmmm a forum full of male flashers!
     
  16. Alex Hawley

    Alex Hawley Member

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    Now Aggie, there you go opening up a realm of possibilities.
     
  17. Seele

    Seele Member

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    I always have more than one enlarger in the darkroom; when required I set up another for "flashing" which I prefer to call "pre-exposure", which is a way of hyper-sensitising the paper.

    What I do is to have the other enlarger set up in a repeatable way, for instance, racked to maximum column height, lens standard racked to top position, minimum aperture set on lens, etc etc. Then I do a test strip with a Durst test strip gadget and process it normally. Once the test strip is ready I examine the steps to identify the greatest exposure the paper can take before registering a density on the paper, and that's my pre-exposure for this batch of paper, which I write on the box.

    In that case, any additional image exposure will start registering on the paper so as to increase highlight details. As this is forcing a linear exposure into the log image exposure, it has practically no effect on the midtones and shadows.
     
  18. Ka

    Ka Member

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    Les McLean's article on Flashing is Excellent!!!!

    Anyone who is still curious about flashing should do to read it.

    I have saved it and printed it out to share with my flash-needy colleagues.

    ka
     
  19. glbeas

    glbeas Member

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    Les and Don, I have a question about flashing VC paper.
    What are the qualitative difference between flashing with the 3 filter or no filter, just the 5 filter or just the 0 filter? I've seen little mention of any testing on this aspect and was curious of any results gotten so far before I start experimenting myself. I seem to have so little time in the darkroom lately it's going to be a while before I have a complete set of results on the paper I want to use.
     
  20. Donald Miller

    Donald Miller Member

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    Gary,
    You raise an interesting question. I haven't done any experimentation along the lines that you suggest. My initial thoughts are that there may be a different result between the hard and soft filtration. The hard filtration would seem to be counter the result that one wants to obtain.

    What we are doing in preflashing the paper is bringing the exposure threshold of the paper into play sooner then it would if a normal exposure were done. This emulsion that is most involved here is the low contrast (yellow or green light) emulsion rather then the higher contrast (magenta or blue light) emulsion. Since the preflash exposure affects primarily the highlight regions of the print, the filtration that would seem to be effective would be soft or no filtration. As we move toward 3 or 5 the emulsion that we wish to addresss is being increasingly removed from the process.

    Those are my thoughts based, as I said, on no testing. Good luck.
     
  21. glbeas

    glbeas Member

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    I can see the reasoning behind the low contrast flash. What I was thinking concerning the high contrast flash was to bring highlight local contrast up. I suspect the threshold exposure for each emulsion layer is going to be different and differing contrast filters will give a different tonal separation in the highlights. This is all just theory right now and the reality may be miles away but I think it's worth looking into.
     
  22. Donald Miller

    Donald Miller Member

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    I understand what you are wanting to do. I would mention, however, that preflashing of paper is inherently working against highlight tonal separation. It is by nature compressing highlight tonal values downward off the shoulder of the paper's curve into the upper midtone regions.

    The other way to increase local contrast in the midtone and highlight tonal range and not exceed the paper's exposure scale is through unsharp masking. Since this is proportional to camera negative density, it tends to bring shadow density upward and tend to leave highlight density as it exists. The mask film base plus fog as it affects highlight density can be ignored in this instance since it is a constant throughout the mask.

    An unsharp mask does not require extensive enlarger capabilities (such as a registration system). It can be produced very easily in the darkroom using ortho lith film and it produces repeatable results. Typical peak density on an unsharp mask will be in the .15-.35 range. This allows us to then print the mask-negative sandwich at a higher contrast range or paper grade then the negative itself would normally be printed. This has the effect of increasing local contrast while maintaining overall contrast.

    I personally think that, considering human visual tendencies, we are accustomed to seeing more separation in highlights then in shadows. For that reason, when we view a print, the effects of shadow compression are less troublesome then compression of the highlight values through preflashing of the paper. However, I would go on to say, that no blanket assessment can be made in all cases. Since each image must be evaluated on it's own merits.

    There is no "free ride" in any of the these manipulations of the paper exposure scale. Since that would indicate an ability to depart from the laws of sensitometry. We can, however, affect the scale so long as the overall scale is not exceeded.
     
  23. Les McLean

    Les McLean Subscriber

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    glbeas wrote:
    Les and Don, I have a question about flashing VC paper.
    What are the qualitative difference between flashing with the 3 filter or no filter, just the 5 filter or just the 0 filter? I've seen little mention of any testing on this aspect and was curious of any results gotten so far before I start experimenting myself. I seem to have so little time in the darkroom lately it's going to be a while before I have a complete set of results on the paper I want to use.

    I have tested flashing VC paper with different filters and my conclusion is that there are no benefits and this has been confirmed by Richard Ross of RH Designs. My tests were assessed by my eyes and personal judgement which is the way that I make my prints, Richards were much more scientific for he is a Dr of Electronics as well as a fine photographer and his tests agreed with mine.[/quote]
     
  24. glbeas

    glbeas Member

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    That's quite interesting Les. Any idea why this happens to be so?
     
  25. mobtown_4x5

    mobtown_4x5 Member

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    I find the "unsharp mask" interesting, but I don't understand exactly how it works, or how noticable the effect/improvement is in practice.

    Does anyone have a gallery image example where an unsharp mask was used? And/or even better, a masked/unmasked set for comparison?

    Matt
     
  26. Donald Miller

    Donald Miller Member

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    Unsharp masking is a technique in that an unsharp low contrast and low density positive is made of the camera film negative.The compression of the original camera negative density scale is directly proportional to the peak density of the mask.

    The method that I use is to place a sheet of ortho lith film (Freestyle or Photo Warehouse) emulsion side down on a sheet of black paper. (this is important since this film has no antihalation coating). On top of this sheet of lith film I lay a sheet of fixed and unexposed film or clear acetate. On top of the acetate I lay the camera negative emulsion side up. On top of this is placed a sheet of Duratrans or similar untextured diffusion material. This is then exposed with the enlarger. Typically with my Saunders 4550 VCCE with the enlarger head at 8X10 enlargement the times will be about 16-20 seconds at F16. The lith film is developed in Dektol 1-30 for 2 1/2 to 3 minutes, fixed and washed. The mask peak density should be .15 to .35 This mask is best evaluated by laying it on a sheet of white paper. To evaluate it by light transmission does not work well since the density of the mask is so low. If one does not have a densitometer the density can be evaluated by comparison to a .30 ND filter.

    The effect is obtained by printing the mask in registration with the camera negative. The registration is not ultra critical since the mask is unsharp.

    Because the overall camera negative density range will be compressed by the amount of the peak density of the mask, the contrast grade of the paper/filtration can be increased without exceeding the papers exposure scale. This has the effect of increasing local contrast and hence a greater "glow" from the image. Another benefit of an unsharp mask is that it increases apparent sharpness due to edge effects.

    I don't have anything currently posted depicting the effects of this practice. I have had images posted in the past that have had unsharp and also sharp masking utilized.