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Pre and Post Flashing
Les McLean
17th December 2008
PRE AND POST FLASHING

Contrast control is the key to making the fine black and white print. Clearly, there are many other considerations, factors such as tonal range, image size print colour to name just three, all play a very important role in the search for the ultimate...
  #10  
By Trevor Crone on 18th December 2008, 12:52 PM
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Quote:
Originally Posted by Dave View Post
I have found that flashing with the negative in place is not always as successful as flashing with white light. I put this down to the fact that no matter how thick the diffuser I am still trying to flash with a defused image which varies the light intensity in proportion to the negative density.
The effect can best be seen when exposing pen lines. If they are exposed though a diffuser with the negative in place, one gets a graduation of tone (which may range to black) instead of a pure even black that is obtained using a pure white light.
This indeed sounds logical and I've been wondering how the various densities of the negative will affect the end result, particularly with a heavy 'flash' to the point of fogging.
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  #11  
By lee l on 18th December 2008, 04:43 PM
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The qualitative difference between using opal glass or perspex and a source like the RH Designs escapes me. Both are effectively perfectly diffuse non-image forming sources, analogous to a Lambertian reflective surface, although the RH Designs may effectively be a somewhat larger source in some circumstances. I can't imagine that there would be any difference in flashing effects between collimated light from the enlarger, diffuse light from a diffuser below a negative or an RH Designs flasher, especially if all were done at a level below threshold exposure (which is the aim of the flashing method under discussion). I can imagine that a large diffuse source used to make penlines, using some covering for the paper and the easel blades, might produce varying density with any significant thickness in the easel blades or material used to block the image area. The diffused source could produce soft edged shadows (and therefore varying print density) from the thickness of the blades and covering material if the light source were not directly above the penline being produced.

I have heard of people using lights bounced off a darkroom ceiling for a print flashing exposure(taking care that the enlarger head doesn't cast a shadow on the paper). Certainly this would be qualitatively quite different from collimated enlarger light with no negative in place and no diffuser. And yet it's reported to work well for flashing.

Obviously my imagination isn't the final arbiter in matters like these, so perhaps experiments are in order if anyone desires some sort of proof that there's something other than a quantitative difference in flashing for improved print highlight detail with diffused or collimated light. Has anyone used both methods and found a difference? I haven't ... yet.

Perhaps it's a difference in our diffusing materials.

Lee
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  #12  
By lee l on 18th December 2008, 05:03 PM
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Just another thought about the degree of diffusion used or required for flashing with a negative in place.

If there is any trace of image forming light in your flashing source (as with insufficient diffusion and the negative still in the carrier), then you are giving a relatively greater flashing exposure to the shadow areas of the print, which is not at all the desired effect. The goal (barring special treatment for certain prints) is to achieve an even overall exposure just below the threshold of the paper. One instructive test might be to make a longer "flashing" exposure for mid-tone density on the paper with your flashing diffuser and negative in place, and perhaps with a high contrast filter or high contrast grade of paper. If that test print exhibited any variation in density across the paper from image forming light, then you might need more diffusion when flashing with a negative in place.

Lee
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  #13  
By Rob Archer on 8th January 2009, 06:50 PM
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Excellent article, Les. I've fallen in love with Kentmere Bromide, which as a graded paper can present challenges - so flashing is a good weapon in the armoury. I must get one of those RH Designs paper flashers. I currently use a diffuser under the enlarger lens which must be too dark/thick as my flashing times are often 30+ seconds.

Rob
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  #14  
By Andrew Bartram on 9th January 2009, 10:05 AM
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Les

I carry out a Max flash test annually as part of my safelight testing process. From this I always have up to date flashing info at hand (using my second enlarger by the way). I am never sure however if flashing should be carried out at "no filtration" or slightly softer, say g 0 or g1. Does it make any difference?
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  #15  
By Les McLean on 13th January 2009, 07:47 PM
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Quote:
Originally Posted by Andrew Bartram View Post
Les

I carry out a Max flash test annually as part of my safelight testing process. From this I always have up to date flashing info at hand (using my second enlarger by the way). I am never sure however if flashing should be carried out at "no filtration" or slightly softer, say g 0 or g1. Does it make any difference?
Andrew, using VC filters makes no difference to the result despite the number of printers who claim that it does. Any white light source that can be accurately timed for consistency is all that is needed.
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  #16  
By RH Designs on 13th January 2009, 07:55 PM
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Quote:
Originally Posted by Les McLean View Post
Andrew, using VC filters makes no difference to the result despite the number of printers who claim that it does. Any white light source that can be accurately timed for consistency is all that is needed.
Les - soft to medium grade filters are indeed no different to using white light, but we found that use of harder grades (3 and upwards) does - it actually prevents the flash having any useful effect. White light and soft filtered light does change the response curve of VC paper, but hard light does not, it simply increases overall exposure. Chris can show you a graph if you like .
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  #17  
By Andrew Bartram on 15th January 2009, 08:12 AM
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Les and Richard

Thanks for that

Andrew
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  #18  
By Gavin on 29th July 2012, 09:03 PM
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A very interesting article and thank you to all contributors.
To a newcomer such as myself the technical aspects of manually printing are exiting and informative to read.

That'll be a paper flasher on the shopping list!
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  #19  
By tjendezutter on 12th October 2013, 10:12 AM
Default FLASHING

i've tried the flashing test first on my Durst M605 but with the times 2-4--6-8-10-12- the result was dark .There is no need to put a negative in the holder to do the testproof?
Second question .Can I manage the flashing when the first enlarger is a Durst M 605 and the second to make the image is a Krokus 66 which required much longer times ... beginning at 60 seconds ...
I've ordred a couple of new bulbs for the Krokus maybe I can make the times shorter ...
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