Questions: Photographic Chemistry
From Silvergrain Labs
I frequently receive questions, which I think is of public interest. This page will be used to post such answers. Please send questions to rs+chem@silvergrain.org, not any other email address I use (because emails will be misplaced before I have a chance to answer them).
Questions related to my products will be answered on silvergrain.info page.
Thanks,
Ryuji
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Wanted: inoperative Konica Hexar AF for parts
I'm looking for an inoperative Konica Hexar AF (any variety), in any condition for parts. I acquire a camera in good condition but with broken circuitry and I am certain that the problem is in the resistor network used to encode the aperture information. Specifically, I need this part:
I can take just this part (and three screws to hold these pieces down) or the whole camera. If you have an inoperative Hexar (beyond economical repair) and can give it to me, pleaes let me know!!
Ryuji 19:27, 17 November 2007 (EST)
Microphen alternatives
Years ago, I once used Microphen as a general purpose developer. It is a bit more grainy than D-76 or ID-11, but it gave better shadow details when the film was shot at the nominal speed printed on the box. I eventually moved away from Microphen because I started research on ascorbate-based developers.
Among the published formulae, Ilford replenishing developer is the closest to Microphen and it develops just like Microphen. Published ID-68 formula is a different developer. Despite common belief, Ilfotec DD-X is not a liquid version of Microphen. Although the difference may be small, DD-X is slightly more finer grained and less speed-enhancing, making DD-X better suited as a general purpose developer than Microphen. Development times for Microphen and DD-X are also different.
In my practice, I have moved away from hydroquinone and I have been using a speed-enhancing developer, whose formula has not been published. This developer will be released from Digitaltruth in the near future. This developer gives excellent tonality from slow films (such as APX25, Pan F Plus, T-MAX 100 and Acros 100). It also has excellent speed enhancing property (with finer grain than other speed-increasing developers) when used with fast films, and it is also ideal for push processing when the film's native speed is insufficient.
Therefore, if you need the processing time and the quality of negative to be photographically identical, I see no other option than mixing the Ilford Replenishing formula yourself. Ilford Ilfotec DD-X or my new developer may be of interest if you are seeking negatives with better shadow details without having to mix from raw chemicals.
Ryuji 20:39, 17 November 2007 (EST)
Can you replace hydroquinone with Vitamin C?
It depends.
In many PQ and MQ type developers, the role of hydroquinone may be played by vitamin C (ascorbate) or isoascorbate, but the formula will need careful readjustment. Once such a substitute is made, you will realize that ascorbate version does not keep well, unless a certain kind of stabilizing technique is used. This further complicates the formulation of the developer.
The role of hydroquinone may not be played by ascorbate or other related compounds in the following types of developers:
- classic hydroquinone-only lith developer
- very slow, very warmtone print developer
Ryuji 20:39, 17 November 2007 (EST)
Why darkroom chemicals shouldn't go to a septic system?
First of all, this has a lot to do with regulation of septic system in your town. In most areas where septic system is used, photographic chemical waste is specifically prohibited. So, any technical consideration will have to be reflected by the change in the regulation first, before any photographic chemicals may be legally disposed of through the septic system.
The reason why photographic chemicals is banned is probably because septic system cannot sufficiently decompose and remove some compounds in photographic chemicals. These compounds may go straight through the septic system and discharged to the environment at best, but it can be worse. Some chemicals can easily disturb the bacteria used in the tank. In this case, not only the problematic chemicals get released to the environment, but also are other stuff that are usually sufficiently treated by the tank.
It is best to avoid disposing photographic chemicals into a septic system. The least expensive way to dispose of chemical waste is to accumulate the waste and bring it to the hazardous waste collection program of your town, or bring it to a nearby sewer system. Licensed chemical hauler is also a recommended option.
Ryuji 20:56, 17 November 2007 (EST)
