gainer
Subscriber
- Joined
- Sep 20, 2002
- Messages
- 3,703
Let me get this straight. I NEVER said that original silver content, before exposure and development, had any bearing on the density of the developed image except to limit the maximum attainable density. The developer used does have a bearing, no matter what the silver content is. Further, the developer can impose its own limit on maximum density by removing silver during the development process.
The man was looking for information on silver content for one reason or another. The photometric equivalent has a bearing on the amount of silver contained in exposed, developed and fixed black and white film. Whatever was in it before exposure, development and fixation has no bearing on how much is in it now. Neither does the process by which the density came to be. I quoted the photometric equivalent found by Hurter and Driffield, and the statement of Hardy and Perrin at a later date. I made no pronouncement of infallibility. If we know the actual photometric equivalent of silver and the average density of the film whose silver we want to recover, we can get a pretty good estimate of the amount of silver we can recover per unit area of the film. No matter what we think we know, we will not have precise knowledge until the processing to recover the silver is completed.
If the relationship between maximum density and silver content in the final image is not fixed for any given sensitive material, positive or negative, given the same processing, then we have no basis for charts of contrast vs time and temperature of development. I am restating this fact in different terms so you will be able to grasp my reasoning. I am not stupid, nor has anyone who knows me implied that I am. I have written technical reports for NACA-NASA and have served as chairman of editorial committees for others. I have presented technical papers at manual control conferences.
You will forgive me, I hope, for not looking up what Ron Mowery has to say about this. He has a penchant for contradicting anything he thinks I said.
The man was looking for information on silver content for one reason or another. The photometric equivalent has a bearing on the amount of silver contained in exposed, developed and fixed black and white film. Whatever was in it before exposure, development and fixation has no bearing on how much is in it now. Neither does the process by which the density came to be. I quoted the photometric equivalent found by Hurter and Driffield, and the statement of Hardy and Perrin at a later date. I made no pronouncement of infallibility. If we know the actual photometric equivalent of silver and the average density of the film whose silver we want to recover, we can get a pretty good estimate of the amount of silver we can recover per unit area of the film. No matter what we think we know, we will not have precise knowledge until the processing to recover the silver is completed.
If the relationship between maximum density and silver content in the final image is not fixed for any given sensitive material, positive or negative, given the same processing, then we have no basis for charts of contrast vs time and temperature of development. I am restating this fact in different terms so you will be able to grasp my reasoning. I am not stupid, nor has anyone who knows me implied that I am. I have written technical reports for NACA-NASA and have served as chairman of editorial committees for others. I have presented technical papers at manual control conferences.
You will forgive me, I hope, for not looking up what Ron Mowery has to say about this. He has a penchant for contradicting anything he thinks I said.