Before digital, I used to buy film in a store/shop saying "nnn ASA"
Then came digital and the 'net': now virtually everyone writes "ISO nnn"!
I understand that everybody and his dog knows what is meant by either ordering - but what if anything caused the transition?
Hi,
The International Standards Organization caused a lot of terminology changes over time. Not just things photography related.
Stan
Amateur Photographer
Professional Electronics Development Engineer
Interesting question that I'll admit I never thought about, but will provide my thoughts:
ASA is a reference to a fixed trait of an object, in this case, film. Yes, we could set the camera to a different ASA speed for special situations, but that usually required adjustment in processing later. The film itself obviously never changed and was defined by that number.
In the digital world, ISO is merely a variable setting, like many others in our cameras, and arguably reads better with the setting name first and the chosen value after.
From google AI:
Before the standardization of the ISO (International Organization for Standardization) film speed system in the 1970s, ASA was the primary standard used to measure film sensitivity to light in the United States and many other regions.
ASA (American Standards Association) and ISO are functionally identical in photography; for example, 100 ASA film is the same as 100 ISO film
The cause seems to be clear from first quote.
PS. I was used to GOST (государственный стандарт Союза ССР) and german films were measured in DIN (Deutsches Institut für Normung) :)
Hi,
There was a time when the film package stated it as ASA/ISO. I suppose to get folks used to the idea that they meant the same thing. Of course, the number was used on many cameras to set the metering to match the film. But one didn't change it while shooting until one changed the film to another sensitivity.
My early digital cameras all had film bodies with digital backs. The earliest ones didn't sport a connection between the two to automatically set the sensor ISO from the camera control. So that could lead to a mismatch far too easily. Later models saw the camera makers produce modified film bodies which then altered the sensor ISO from the camera ISO control.
In reality, the sensors have one or two actual equivalent sensitivity and the changing of the ISO isn't much more than slight of hand for the digital processing engine.
Stan
Amateur Photographer
Professional Electronics Development Engineer
ASA was regional (USA) designation for film sensivity like DIN was in Germany. In 1974 all has been changed to ISO (International Organization for Standartizaton) to create universal measurment for film sensivity.
Makes sense, thank you ... and common vernacular often lingers long after Standards change!
What is the "sensor ISO" of a digital back, please?
Hi,
Whatever the manufacturer of the back said it was. In the case of the Kodak unit I had in mind, it was ISO 80. That was not changeable. However the Nikon film body had the ISO control which was changeable, but one needed to leave that at 80 for the metering to be somewhere near correct.
That wasn't always an issue, but then I would use the body with film and change it, then forget to change it back when I reinstalled the body onto the digital back.
Stan
I just checked the rolls of film I have in the fridge. They're all marked with ISO/DIN. I guess that's the universal marking now. But this reminds me of other scales. GE in particular. Somewhere around here I think I still have a GE meter. This site has some info on GE and several other rating scales, including GOST.
Thank you, Stan.
Hi,
Another item of note for the older stuff: No rear LCD to eyeball. So, the camera body metering was of more importance. Later, with a screen, we had another tool to gauge exposure with.
Stan
