I actually posted this on the forum for beginner questions, and i hope I am not breaking any taboos by repeating it here. I thought it worth doing so because a lot of experienced photographers may not use that forum, but might find this worth reading. I hope you do!
I continuously come across folks who spell the letters associated with sensor sensitivity and thought it was apropos in this forum to set the record straight. How much it will come up in conversation varies a lot, but as an educator myself, I use it frequently: both in explanations and analysis of others' images.
Many people think that ISO is an acronym for a body called the International Standards Organization and thus spell it out. Actually, it is NOT an acronym, there is no such body name International Standards Organization, and it is a word that is supposed to be pronounced
as a word!
So, let's find out what the actual derivation is. Back in the 1940's, as global trade began to flourish again after WWII, national standard bodies such as the German DIN (Deutsches Institut für Normung), and ASA (American Standards Association) - in fact, 165 national standards organizations, formed an umbrella group, for which they had to find a name. The intent of the group was to create documents that could assure consistency across the globe on measurements, values, and standards for process, products and protocols. Because each country would likely create a different name for the group based on their language, it was decided to create a name that was short, and easy to pronounce. The one they chose is based on the classical Greek word for 'same".
To quote from the website Target Tech Website:According to ISO, ISO is not an abbreviation. It is a word, derived from the Greek Isos, meaning "equal," which is the root for the prefix iso- that occurs in a host of terms, such as isometric (of equal measure or dimensions) and isonomy (equality of laws, or of people before the law). The name ISO is used around the world to denote the organization, thus avoiding the assortment of abbreviations that would result from the translation of "International Organization for Standardization" into the different national languages of members. Whatever the country, the short form of the organization's name is always ISO.On film canisters it was common to see references to DIN, and ASA, and some were also given ISO references. When digital came along, ISO was asked to provide international standards relating to the measurement and sensitivity of sensors, and this is alone is seen in such references. There are two such documents that I can find on a casual search:
ISO 12232:2019: Photography — Digital still cameras — Determination of exposure index
https://www.iso.org/standard/73758.html and
ISO 15739:2017: Photography — Electronic still-picture imaging — Noise measurements:
https://www.iso.org/standard/72361.html?browse=tc What confuses many is that the word is capitalized. This is because ISO is used frequently in long, technical documents and being able to identify ISO references is assisted by the fact they are capitalized - a feature in the printing industry known as SHRIEKING. It makes the words stand out, but does lead to the temptation to mis-identify it as an acronym, or based on one. It is also registered as a trade mark and copyright symbol. Furthermore, by capitalizing the word, it is separated from a colloquial use of the word that might be found in search engines or tools. ISO are quite explicit and clear on this, as they say in their own web page ABOUT US: ISO: ABOUT US which I quote from below:
IT'S ALL IN THE NAME
Because 'International Organization for Standardization' would have different acronyms in different languages (IOS in English, OIN in French for Organisation internationale de normalisation), our founders decided to give it the short form ISO.
ISO is derived from the Greek 'isos', meaning equal. Whatever the country, whatever the language, we are always ISO.Finally, what ever happened to DIN and ASA? Well DIN is alive and well and still issuing standards. ASA had to get renamed as it clashed with the acronym for the Audiology Society of America and became ANSI -the American National Standards Institute.
SO... to summarize: ISO is a term based on a word and should be pronounced as such.
Doubtless, there will be many who are entrenched in their old use of spelling it out, and I doubt that for some this will change their mind, but the derivation and intent are crystal clear and well documented!