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What happens to neg quality as dev becomes exhausted?
I want to shoot some resolution shots to test my LF lenses. If I use
D-76 that has been spent developing other negatives, what can I expect from the negatives developed beyond the rated capacity? The qualities in a negative that the developer impacts are contrast, maximum density and accutance (maybe more?). I am guessing that as developer action declines, max density suffers, and therfore contrast. Could more frequent agitation or increased temperature help this? The point is avoid creating more water pollution for negatives that will never be printed, but if using old developer makes it impossible to judge the quality of the image, then it will not serve as a good indication of lens quality. Also, what is the dark precipitate seen in used developer that has sat for a while? Thanks, Scott |
#2
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What happens to neg quality as dev becomes exhausted?
You don't say how you are performing these tests but accutance can affect
the perceived sharpness of the results. I know we're all doing our part to help the environment on a micro-scale but the effort expended on lens tests would require me to suggest you use fresh developer for each test for more repeatable results. Note that most developer components fall into the categories of harmless or bio-degradable, most of the concern today is about silver compounds. Most darkroom chemical makers will concur that the amount of effluent that a home darkroom discharges will never harm even a micro-ecosystem like a septic system much less a municipal sewage system. Having said that, and with no desire to spark another long thread on environmental issues, I must also say that the possibility is quite good that some, pencil-necked, paper pusher in a city office would have a field day if you actually tried to be a good guy and comply with all the regs (not to mention the fact that you'd go broke). When I saw the local lead acid battery rebuilder washing down his shop floors into the local storm sewer and drive by the local packing plant daily gagging and puking because of the smell, drive by the local metal plating plant wondering what they are putting into the air and ground water and observe the soot and crap coming out of the local coal fired power plants I gave up on micro-ecology and decided to wait until local government reins in the big boys. The difference of course is jobs and "the economy" local government will do nothing to stop large scale pollution since it might upset the local job market. In the meantime I know that my hobby darkroom (20 to 100 rolls of film per month--hey even I get busy once in a while) is doing very little to harm the environment. Kodak, Ilford and everyone else that went on record on this issue has said so. Even so, I'm a careful worker and frugal in my use of darkroom materials and am careful about what I put down the drain. -- darkroommike "tbrown" wrote in message oups.com... I want to shoot some resolution shots to test my LF lenses. If I use D-76 that has been spent developing other negatives, what can I expect from the negatives developed beyond the rated capacity? The qualities in a negative that the developer impacts are contrast, maximum density and accutance (maybe more?). I am guessing that as developer action declines, max density suffers, and therfore contrast. Could more frequent agitation or increased temperature help this? The point is avoid creating more water pollution for negatives that will never be printed, but if using old developer makes it impossible to judge the quality of the image, then it will not serve as a good indication of lens quality. Also, what is the dark precipitate seen in used developer that has sat for a while? Thanks, Scott |
#4
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What happens to neg quality as dev becomes exhausted?
"Robert Feinman" wrote in message ... In article .com, says... I want to shoot some resolution shots to test my LF lenses. If I use D-76 that has been spent developing other negatives, what can I expect from the negatives developed beyond the rated capacity? The qualities in a negative that the developer impacts are contrast, maximum density and accutance (maybe more?). I am guessing that as developer action declines, max density suffers, and therfore contrast. Could more frequent agitation or increased temperature help this? The point is avoid creating more water pollution for negatives that will never be printed, but if using old developer makes it impossible to judge the quality of the image, then it will not serve as a good indication of lens quality. Also, what is the dark precipitate seen in used developer that has sat for a while? Thanks, Scott Generally as developer get used it has less active ingredients so it takes longer to develop to the same contrast. There may also be some effect from the oxidized developer by products left from previous uses. Kodak used to give times for reuse of D76 without replenishment, perhaps you can find them someplace. The problem is one doesn't really know how much to increase the developing time with each use. Partly it depends on how dense the prior films were. If you want to conserve water want not replenish the developer. You can buy D76R or mix it yourself. Another approach is to use a standard developer like D76 diluted as a one shot. This way you always have fresh developer for each batch. Black stuff floating in developer is dissolved silver caused by the silver solvent added to the formula to promote fine grain. It does no harm, but can leave spots so it should be filtered out. If you have a lot you should be using fresh developer. Why spoil all your hard work and expensive film over a few cents worth of developer? -- Robert D Feinman Landscapes, Cityscapes and Panoramic Photographs http://robertdfeinman.com mail: The effects of use are more complex than this. When processing reaction products of development and some ions from the halide are left in the developer. The most important reaction product is probably bromide. Bromide acts as a restrainer, especially for silver halide crystals that have received low exposure. The result is some loss in shadow detail even when development time is incresed to achieve a constant contrast. The effect may be more noticable in D-76 than some other developers because D-76 contains no bromide where many other developers do for because they need the fog suppression. D-76 tends to be long lived because the two developing agents, Metol and Hydroquinone, tend to regenerate each other. D-76, and many other developers, can be kept going for very long periods of time by adding a replenisher. Kodak sells a packaged replenisher for D-76 as D-76R. A small amount is added for each film developed. Ideally, some method of testing for consistent development should be done, but even just keeping the volume up will stretch the developer life. The advantage of a replenisher is that contrast will remain essentially constant once the developer reaches equilibrium. However, the accumulated bromide will still reduce shadow detail somewhat. D-76, in one variation or another, was the standard developer for motion picture B&W negative processing for many years. It was used in automatic machines with automatic replenishment. Even the current developer recommended by Kodak for this application is really a variation of D-76. The black precipitate may be dissolved halide which has become metallic silver due to exposure to light, or it may be particles of gelatin from the emulsion. Sometimes this is also caused by micro-organisms growing in the developer. Filtering will help but I agree with those who think developer is cheap compared to film and to the cost of lost pictures. Dump it. -- --- Richard Knoppow Los Angeles, CA, USA |
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