Perceptol & The Microdol Substitute Formula.

newcan1 said:

And one more question: Could I use potassium chloride instead of sodium chloride?

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No difference except for molecular weight. Adjust for them and things are ok.

PE

I apologize for an off topic tangent, but this thread brought a question to my mind based on the responses: What's the difference between a Photo Engineer and a Photo Chemist? These responses seem more Chemistry than Engineering to me. (Spoken as a Mechanical Engineer).

Craig said:

I apologize for an off topic tangent, but this thread brought a question to my mind based on the responses: What's the difference between a Photo Engineer and a Photo Chemist? These responses seem more Chemistry than Engineering to me. (Spoken as a Mechanical Engineer).

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Possibly that a Photo Engineer knows, not only the relevant chemistry, but also some spectroscopy, theory of color perception and color management, possibly optics, etc. In other words a task-oriented array of competence rather than defined by an academic field and degree.

And yes, maybe PE is the person to answer, but an outsider's opinion might be given credit for objectivity.

A Photo Chemist is one who works on reactions in chemistry that are influenced by light or cause light. Thus, a firefly is a photo chemical reaction as is a chemical flare stick. A Photo Engineer designs photographic processes, films and papers from start to finish including coating. So, I know less and less about more and more and finally, when I retired, I knew nothing about everything!

PE

Photo Engineer said:

when I retired, I knew nothing about everything!
PE

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You should run for office. Perfect qualifications.

No, a politician knows everything about nothing. Just the opposite.

PE

Photo Engineer said:

A Photo Chemist is one who works on reactions in chemistry that are influenced by light or cause light. Thus, a firefly is a photo chemical reaction as is a chemical flare stick. A Photo Engineer designs photographic processes, films and papers from start to finish including coating. So, I know less and less about more and more and finally, when I retired, I knew nothing about everything!

PE

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That's a form of "overdriven" understatement - isn't it ?

with regards

Photo Engineer said:

No, a politician knows everything about nothing. Just the opposite.

PE

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Thats also "overdriven" understatement because it is much more worst wich most
politcians.
.....

That does not translate well, I guess.

Maybe there is no Pravda in Isvesta and no Isvestia in Pravda works better.

PE

OK, so I made a batch of homebrew Perceptol (but using potassium choride), and I have developed a test roll of GAF Super Hypan in it, which I am guessing expired in the early 1970's. Originally rated the old ASA 320 (modern ISO 400), this film has lost speed, and in D76 it can be shot at ISO 100. With the Perceptol, it looks like the best result is at ISO 25, although 50 also looks useable. Grain looks noticeably smaller, although I won't really be able to gauge the look of the film until I make some prints. The grain when developed in D76 1:1 was not only course, but also ugly, in my opinion. I wonder if I should try half developing in Perceptol, and then finish up with D76 or something like it, to see if I can get a bit more speed but still with acceptable grain. I am also waiting for a batch of Xtol to arrive.

You will get a little boost in the speed department with a 1:1 or even a 1:2 ratio of Perceptol. The grain might increase slightly along with the speed. JohnW