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> Bromide drag |
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#1
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Bromide drag
Although it's something I've never seen, I've read a little about the phenomenon and the explanations given and they seem to clash with my limited knowledge of chemistry and the behavior of solutions. Has any real research been done on this or are the explanations no more than someone's pet theories?
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#2
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My first thought was it is a new type of cigarette but then why would you ask here In answer to part of your question is I have not heard of it. Is it known by a more common title?
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Mitch http://photomi7ch.blogspot.com/ If you eliminate the impossible whatever remains no matter how improbable must be the truth. |
#3
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Some of my films have exhibited streaking or flow marks over the years that I've put down to bromide drag. So in my view it is a real phenomenon, fact not fable.
In order to try and prevent streaking, flow marks or other uneven development irregularities I do a number of things; I give a pre-wash of 5 mins for large format film and introduce change into the rotation and circulation of chemicals during development. It hasn't happened for a long time since.
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MartyNL “Reaching a creative state of mind thru positive action is considered preferable to waiting for inspiration.” - Minor White, 1950 |
#4
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It's more prevalent when using stand or minimal agitation development because of the lack of developer circulation/agitation.
I stopped suffering from it as my technique improved, especially around agitation. Mike |
#5
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I had one disaster with it several years ago. I was trying to develop 5 120 films in a big Patterson tank using Stoeckler's 2-bath developer. It's usually pretty failsafe but, because the second bath (borax) is effectively stand-development I got bromide drag - very visible streaking across the negatives. The top couple of films were ok and a few frames on the middle one but the bottom two were unusable. I certainly wouldn't do multiple films by that method again!
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#6
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research into Bromide Drag
Quote:
I worked on the SmartLab processor project in the 1990s, always with the knowledge that the result would have to pass inspection at Kodak's research labs at some point. Fortunately I, too, had access to a lab-grade densitometer. In SmartLab, films were loaded into stainless-steel spirals, threaded onto a rotating shaft in a stationary cylinder. Tests began with Ektachrome film and E6 chemistry but continued with B&W film (quicker and much cheaper). The film was exposed to a very high-contrast checkerboard pattern and processed in a variety of developers. The choice of developer made no difference, although we settled on Kodak Xtol 1+1 because of the tolerance of most film types in it at relatively high temperatures. The exposed pattern showed streaking when the spirals were rotated consistently in one direction. The streak is derived partly from local developer exhaustion and partly from the restraining action of bromine ions released during development. Unfortunately both conditions act is the same way. From memory, the change in density was as much as 0.08D - quite visible. So we turned the spirals in one direction for about 20s and then changed direction. If the period of clockwise rotation was the same as anticlockwise, so that the change of direction always occurred at the same point, there was a curious measured patchiness where the change occurred, not easily seen by the naked eye. So we rotated the spirals longer in one direction than the other, so the patch moved along the length of the 135/36 film and effectively disappeared. The thoroughly oxidised and exhausted developer had to be discarded. We had to slow the rotation during E6 colour development because stain increased the the Dmin by about 0.04D. It, too, had to be discarded to match the Kodak process control strips. The streaking barely showed up on colour negative film (C41). |
#7
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[QUOTE=JOReynolds;132996]Bromide drag is very visible on some early cinema film - that's the era before the first world war.
I remember it very well.That was why I stopped going to the cinema then and haven't been since. Mike |
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