A few more pieces of information.
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When did the industry move from ASA to ISO?
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Only we nerds...........
My ancient Knight Kit CdS light meters came with a pale green filter. Explained by the above notation that CdS is more red sensitive.
My ancient Knight Kit CdS light meters came with a pale green filter. Explained by the above notation that CdS is more red sensitive.
SPD cells are not photovoltaic, but a semiconductor.
… but that’s picking nits and not really pertinent to the discussion.
I haven't heard the words "Knight Kit" in ages. Allied Electronics.
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Good point !
I understood "photovoltaic" in this context as meaning that the cell produces electricity itself, in contrary to the other two cells. That is why I found it not apt using it for the SBC cell. Actually I considered it just as an error at the lay-out stage.
(In Germany "photovoltaic" generally is used in this meaning.)
Well, if one understands "photovoltaic" as light affected semiconduction, then indeed it applies on both, the Selenium and the SBC cell.
But then on the CdS cell too....
In any case, I learned of an another meaning of this term.
I got a great amount of light meters. And even more built into cameras.
I did not come across a green filter on a CdS cells so far. But an interesting observation of yours. Maybe I should check again...
And there was Lafayette Electronics, also a large maker of electronic kits and branded items like radios.
I had a Heathkit color console TV. I bought it used and chose it over other options because of the extensive build and repair manual that came with it.
I had an Allied stereo amplifier and a Lafayette CB radio in the mid-1960s. I remember looking though the catalogs.
I remembering looking through the Heathkit catalog and asking my father if I could buy a color TV kit. He showed a shocking lack of confidence in my soldering skills and turned me down. I was about ten.
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In 1972 I bought a Heathkit Stereo AM FM Radio Amplifier that lasted for years.
MattKing
Moderator
I was in my early teens - also around 1972 - when my Dad bought for my assembly the kit for our family's Heathkit stereo receiver. I used the Heathkit VTVM I built from a kit to help me in putting together the receiver.
Isn't geekdom wonderful?
Also built some Dynakits.
The nurse is bringing in my afternoon Jello treat now.
Don't forget the prune juice!
In the fall of 1963 we had the Cuban Missile Crisis. The whole country was on edge. My parents, pretty frugal decided, "Screw it, we may not be around next year." So they splurged on Christmas presents. I got a four band Lafayette short wave receive kit. My pride and joy for years.
This is not as much a when did the manufacturers change but when was the beginning of the road to the change. From C.N. Nelson, Safety Factors in Camera Exposures, Photographic Science and Engineering, Vol 4, Number 1, January-February 1960.
"There are several reasons, however, for adopting not only a new constant but also a different speed criterion. The fractional-gradient criterion was originally chosen because it has the desirable feature of giving speeds that correlate closely with speeds obtained by practical picture tests. It has the objectionable feature, however, of being somewhat inconvenient and difficult to use. Consequently, a simpler and more convenient criterion, such as that based on a fixed density above fog density, is often desired. Fortunately, as shown by the recent data of Nelson and Simonds, a good correlation exists between fractional-gradient speed and speeds based on a density of 0.1 above fog, provided the development condition's are controlled so that a fixed "average gradient" is obtained. This average gradient is measured on the portion of the .D-log E curve of the film lying between two exposures, E and 20 E, where E is the exposure at a density of 0.1 above fog. The specification of a fixed average gradient in an American Standard would be justified by the fact that such a specification corresponds to the common photographic practice of developing negatives so that they print satisfactorily on a "normal" grade of photographic paper. Thus the adoption of the 0.1 fixed-density speed criterion in combination with a suitable development specification would offer the advantages of convenience and practical significance.
Another important advantage to be gained by adopting the fixed-density speed criterion as part of an American Standard is that this step would encourage eventual agreement on an international standard for photographic speed. The fixed-density criterion has for many years been a preferred criterion in a number of countries. The use of this criterion in the DIN system," for example, is particularly well known."
"There are several reasons, however, for adopting not only a new constant but also a different speed criterion. The fractional-gradient criterion was originally chosen because it has the desirable feature of giving speeds that correlate closely with speeds obtained by practical picture tests. It has the objectionable feature, however, of being somewhat inconvenient and difficult to use. Consequently, a simpler and more convenient criterion, such as that based on a fixed density above fog density, is often desired. Fortunately, as shown by the recent data of Nelson and Simonds, a good correlation exists between fractional-gradient speed and speeds based on a density of 0.1 above fog, provided the development condition's are controlled so that a fixed "average gradient" is obtained. This average gradient is measured on the portion of the .D-log E curve of the film lying between two exposures, E and 20 E, where E is the exposure at a density of 0.1 above fog. The specification of a fixed average gradient in an American Standard would be justified by the fact that such a specification corresponds to the common photographic practice of developing negatives so that they print satisfactorily on a "normal" grade of photographic paper. Thus the adoption of the 0.1 fixed-density speed criterion in combination with a suitable development specification would offer the advantages of convenience and practical significance.
Another important advantage to be gained by adopting the fixed-density speed criterion as part of an American Standard is that this step would encourage eventual agreement on an international standard for photographic speed. The fixed-density criterion has for many years been a preferred criterion in a number of countries. The use of this criterion in the DIN system," for example, is particularly well known."
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