Why some people call the ISO or ASA film speed

[Manuel Madeira]

Hey guys, simple question, why people call the film ISO or ASA film speed, i cant figure it out XD

 

[Old_Dick]

At least in the US, film speed was rated ASA. I have some old film that is rated ASA. I still say ASA with "old friends".

 

[BrianShaw]

Technically, those refer to different standards from different eras. ISO is current standard. . In practice, a lot of folks use the terms interchangeably.

This is a lot of reading but has a lot of the details about film speed history and measurement.

https://en.wikipedia.org/wiki/Film_speed

 

[Nige]

age

 

[AgX]

Basically: ASA , ISO , DIN are all three the names of standardisation institutions which, amongst other things, made photography related standards. And not only ones referring to film speed.

 

[Andrew O'Neill]

There once was just ASA. Some people still say it because it's what they're used to. Kind of like when Apug changed to Photrio. Some people still call it Apug. I call it Photrio, but prefer the name Apug

 

[Bill Burk]

Are you asking why it’s called “Film Speed” in the first place?

Good question!

When photography first started in the mid-1800’s, the photo sensitive material required a lot of light to react to the point where a photgraph would emerge.

With the lenses and cameras of the era, exposure took a long time and people wanted it to be done faster, so that people wouldn’t move while their picture was being taken.

Science started discovering ways to prepare silver and things to add to it which would make it faster.

Speed is a measure of how fast a film is.

In the early days speed was measured in crazy ways with superlatives that didn’t always compare to each other or to what photographers wanted to do.

ISO and ASA are standard speeds that took most of the guesswork out of how fast the film is.

Someone else should elaborate or expand this story because it’s fascinating. Exactly how fast is ‘Super Ultra Fast’? I never found out but I think it might be ASA 12

 

[MattKing]

There once was just ASA.

Unless you looked real close at the box, for the DIN speed .
It was easier to read if you used Agfa film.

 

[wiltw]

Hey guys, simple question, why people call the film ISO or ASA film speed, i cant figure it out XD

I believe your question is why 'film speed', not why 'ASA' vs 'ISO'... it is because it was the attempt to have a single standard to rate sensitivity of Film, after a multiplicity of rating numbers were used in the evolution of light meters. The Wikipiedia article already quoted explains it.

Digital camera sensitivity was made to match the expectations of Film sensitivity, so the successor behaved like its predecessor, and the pre-existing light meters would continue to work for digital sensor as it worked for film.

 

[AgX]

There once was just ASA.

No, there once was just DIN...

Or Scheiner... you name it.

 

[Chan Tran]

Are you asking why it’s called “Film Speed” in the first place?

Good question!

When photography first started in the mid-1800’s, the photo sensitive material required a lot of light to react to the point where a photgraph would emerge.

With the lenses and cameras of the era, exposure took a long time and people wanted it to be done faster, so that people wouldn’t move while their picture was being taken.

Science started discovering ways to prepare silver and things to add to it which would make it faster.

Speed is a measure of how fast a film is.

In the early days speed was measured in crazy ways with superlatives that didn’t always compare to each other or to what photographers wanted to do.

ISO and ASA are standard speeds that took most of the guesswork out of how fast the film is.

Someone else should elaborate or expand this story because it’s fascinating. Exactly how fast is ‘Super Ultra Fast’? I never found out but I think it might be ASA 12

only you answered the OP question. Calling the film sensitivity film speed is like calling a lens with large aperture fast lens.

 

[Kodachromeguy]

There once was just ASA.

Wrong. Google is your 10 sec. friend. Older standards included Scheiner, DIN, BSI, Weston, GE, ASA, and GOST.

 

[FotoD]

Speed in photography is about how fast an exposure can be made.

In the 1840s it could take minutes to expose a portrait with the daguerrotype process. Voigtländer changed this when they started making Joseph Petzvals new lens with a large aperture of f/3.6. Suddenly it was possible to make an exposure much faster, in seconds instead of minutes, which was much easier for both sitter and photographer. In the 19th century lenses with large apertures were called "fast working".

 

[Andrew O'Neill]

I work with EI's.

 

[faberryman]

Calling the film sensitivity film speed is like calling a lens with large aperture fast lens.

Most photographers call a lens with a large aperture a fast lens. It doesn't make a lot of sense, but everyone knows what you are talking about. Let's say you are at a workshop and you mention that your 50mm Summilux is a fast lens; you are probably not going to want hang around with they guy who lectures you about why you are wrong to call it a fast lens. Of course, no one is going to want to hang around with you either because you are talking about your Leica. That's not to say they won't secretly ogle your Leica from a distance, and fantasize about how they might be able to get one too.

Did I mention that my lens is sharp? What's that all about?

 

[BradS]

I work with EI's.

I guess we all do. Most people just don't realize it or think of it that way.

 

[Ian C]

The ASA film-speed system has been in use for many years. The other major film-speed system is the German DIN film-speed system. DIN is less used now than formerly.

ISO is a dual designation that’s written like a fraction as ASA/DIN. For example, an ASA 100 film has DIN designation 21°. Note that the “degree” symbol is part of the DIN designation.

In ISO designation this is ISO 100/21°. In more recent times since DIN film speeds are not much used, it has become common to refer to such a film as ISO 100, which, strictly speaking, is not correct, but has become common usage.

Here is an article that discusses film-speed designations and their customary uses.

https://en.wikipedia.org/wiki/Film_speed

 

[Chan Tran]

The question isn't why calling it ISO or ASA but rather why we call the ISO or ASA rating of a film "Film Speed" instead of "Film Sensitivity" for example? Does the film moves?

 

[Horatio]

Speed is easier to say and spell than sensitivity?

 

[faberryman]

The question isn't why calling it ISO or ASA but rather why we call the ISO or ASA rating of a film "Film Speed" instead of "Film Sensitivity" for example? Does the film moves?

Mine does. That is how it gets from the start of the roll to the end of the roll. Otherwise, you wouldn't need a rewind knob. Film moves faster with a winder and fastest with a motor drive. Some photographers don't like their film to move, so they shoot large format.

 

[mshchem]

https://en.wikipedia.org/wiki/American_National_Standards_Institute

 

[Ian Grant]

Technically the current ISO standard is an amalgamation of the US ASA (& BS - British standard) and the German DIN standard, testing can be with either standard and listed as the equivalent speed.

So a film like FP$ is ISO 125/22º which is 125 ASA/BS and 22º DIN

Ian

 

[beemermark]

ASA (American Standards Association) was in wide spread use around the world. DIN for German National Standards was used in Europe to some extend. The ASA evolved into the ISO (International Standards Organization). ASA and ISO standards were identical until at some point individual standards by independent committees updated them. So for film ISO and ASA are pretty much the same film speed. DIN is based on a completely different scale and not interchangable with ISO or ASA. Most (if not all) film cameras have the speed setting marked as ASA while digital uses the newer ISO setting.

 

[Chan Tran]

Mine does. That is how it gets from the start of the roll to the end of the roll. Otherwise, you wouldn't need a rewind knob. Film moves faster with a winder and fastest with a motor drive. Some photographers don't like their film to move, so they shoot large format.

Yeah mine does too but the speed was determined by the camera fps and not the ISO or ASA rating. Yeah and I remember movie film has the rem jet coating for high speed.

 

[Chan Tran]

Some people call it film speed? Think of it if they don't call it film speed what do they call it.