Tube Developer Experiment Resultsgreenspun.com : LUSENET : Large format photography : One Thread
I've been using homemade developing tubes for 4x5 for nearly a year. According to Darkroom Innovations you can pull the top off at the end of developing time and plunge the tube into a tray of stop bath in room light. Adams however insists in The Negative that light must not reach the film until well into fixing. I've often wondered about this and finally tested it with my customary film/developer combo, HC 110 and Tri-X. I made three identical exposures. Developed the first one in total darkness through 4 minutes of fixing, the second as normal, (film remains in tube but half submerged in stop bath while you spin it in low room light, then fixed for a minute or so in same manner) and the third I pulled out of the tube directly after development and plunged emulsion side up into a tray of stop bath in direct sunlight. I cannot distinguish between the first two negatives but the third is very slightly darker than the others.
If anybody else has run this test I'd be interested to hear the results. I'm going to ignore Adams and keep doing it the way I always have.
-- Erik Ryberg (email@example.com), October 06, 1998
The film should remain in darkness at least into the stop bath. I simply don't see any reason to gamble with fogging the film by turning the light on prematurely. What difference can a few more seconds possibly make?
-- Peter Hughes (firstname.lastname@example.org), October 06, 1998.
The reason is I don't really have a darkroom - just a tiny crowded closet. Spinning the tubes on the kitchen table (after loading them in the closet) is a lot easier than fighting with chemicals amongst our clothes. . .. ER
-- Erik Ryberg (email@example.com), October 06, 1998.
You should retry this experiment again with unexposed film or film exposed to just enough light to produce an even "Zone I" exposure of the entire sheet of film. If you have access to a densitometer compare the readings. What you are looking for is a change in the Base+fog density level. Higher levels of exposure, especially those producing densities corresponding to "Zone V" and above will not not show the fog, it will be hidden in their density; but thinner areas of the film will reveal the unwanted additional fog.
-- Ellis (firstname.lastname@example.org), October 07, 1998.
Erik, I had this same discussion with the salesperson when I purchased the BTZS tubes. Having read their sales pitch, and the product review in View Camera Magazine, I simply could not accept that film would not be fogged if not kept in complete darkness during the various development steps, or at least until part way through the fixing process, as per Adams.
The BTZS folks assured me that as long as the room light was "dim" the BTZS tube cap could be removed after the development step and placed in the stop bath, without damaging the film. As users of the BTZS tubes know, these do not have a pour-in type cap, like daylight tanks. You have to completely remove the cap to change solutions. this is tough to do in complete darkness.
I tried it their way, and my old way in complete darkness, and did not notice any appreciable difference or increase in film-base density when measuring both sheets with my densitometer. Mind you, I used very dim light; just enough to allow me to see what I was doing.
I suspect that had I used normal room light the negatives would have been fogged, or even ruined. And I still cling to the old belief that when using open trays, instead of the tube method which shields film from direct light, exposing film to light before completing the development process would be damaging.
I suppose I'll have to do the test Ellis suggested, with an unexposed sheet of film, to see if Adams' recommendations are well founded. Old habits die hard.
Good luck, Sergio.
-- Sergio Ortega (email@example.com), October 07, 1998.