Why some people call the ISO or ASA film speed

Sirius Glass · Oct 9, 2021

Andrew O'Neill said:
I work with EI's.

EI is for people who have not gotten their cameras CLA'd and light meters calibrated.

Andrew O'Neill · Oct 9, 2021

Sirius Glass said:
EI is for people who have not gotten their cameras CLA'd and light meters calibrated. View attachment 287642

Uh oh I've never done that, actually.

foc · Oct 9, 2021

Does it matter what the ASA. DIN, film speed or sensitivity is, when I don't shoot at box speed???
And I expose for the highlights and develop for the shadow, or is that the other way around?

markjwyatt · Oct 9, 2021

ISO and ASA, though different standards, pretty much end up with the same film speed rating number in the end.

Bill Burk · Oct 9, 2021

Andrew O'Neill said:
Uh oh I've never done that, actually.

After I confirm my film speed is 400 I choose an exposure index of 250 to get the kind of negatives I want. Sounds silly but I don’t choose 250 because I think the film speed is 250. I know it is 400

AgX · Oct 10, 2021

faberryman said:
Most photographers call a lens with a large aperture a fast lens.

It depends on language.

In German for lenses or films I have never heard or read such. The same for exposure times called "speed".

(With the exception of a larger aperture Meyer lens from 1904 called "Fast Worker", so I might have a look at litrture from those years.)

tballphoto · Nov 9, 2021

Bill Burk said:
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

Enterprising photographers of this time period, and even now, simply addapted to photographing clients that wouldnt move no matter what.

They worked at funeral homes.

Sirius Glass · Nov 9, 2021

I still call fixer "hypo", but then again I am smart enough to call Hypo Eliminator, Hypo Eliminator and not hypo. Life is tough, but we still have to use the correct words.

Alan Edward Klein · Nov 9, 2021

Chan Tran said:
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?

We do speak of fast lenses and fast shutter speed, not lens sensitivity or shutter sensitivity. So maybe that accounts for the use of film speed?

benjiboy · Nov 9, 2021

For all practical purposes they are the same.

Dusty Negative · Nov 9, 2021

This has been a pretty humorous read.

pbromaghin · Nov 9, 2021

With there being a couple different interpretations of the question, maybe Mr. Madeira could tell us which question he was asking.

AgX · Nov 9, 2021

The OP actually hinted at "some people" speaking of film-speed.

As far as I can see, all these people are English speaking.

Sirius Glass · Nov 9, 2021

Now I say ISO, but back in the 1960's I was know to say ASA. I never used DIN.

Bronson Dugnutt · Nov 9, 2021

'aye-ess-aye' (sic 'ass-uh') and 'eye-ess-oh' both roll off the tongue much more easily than 'Webermeter' or 'Lambert'. Plus, combining it with the lovely, dimensionless F number and a shutter speed gives a standard SI illuminance measure of Lux.

https://www.pointsinfocus.com/tools/exposure-settings-ev-calculator/

It is a very useful calculation for knowing beforehand what sort of lighting conditions a rig will be able to handle a given minimum shutter speed, maximum aperture, and rated film responsiveness.

AgX · Nov 10, 2021

AgX said:
The OP actually hinted at "some people" speaking of film-speed.

As far as I can see, all these people are English speaking.

Are there other languages where "film speed" and "shutter speed" are used?

miha · Nov 10, 2021

We say "film sensitivity" and "shutter time" respectively. We don't say "fast lens" either, instead "light intensity / power of the lens" words are used to describe it, however I believe this was taken from your language (= Lichtstärke).

AgX · Nov 10, 2021

The same in German (and Dutch).
Alternatively to "shutter time" "exposure time" is used.

AgX · Nov 10, 2021

Sirius Glass said:
Now I say ISO, but back in the 1960's I was know to say ASA. I never used DIN.

I am most surprised by this.
For the the 50-400 ASA range it makes no difference, but beyound that it becomes weird. Being a engineer I would have thought you would go the logarithmic way.

Sirius Glass · Nov 10, 2021

AgX said:
I am most surprised by this.
For the the 50-400 ASA range it makes no difference, but beyound that it becomes weird. Being a engineer I would have thought you would go the logarithmic way.

I DIN use logarithms for ASA then.

Stephen Benskin · Nov 12, 2021

Hollis N. Todd has a pretty good explanation in his book Photographic Sensitometry: The Study of Tone Reproduction and in his entry in Encyclopedia of Photography.

From the Encyclopedia of Photography. "The film speed number was intended originally to measure the fundamental sensitivity of a negative or positive semitrans0arent photographic material. Now, film speed is an index value on a scale for use by photographers in determining the camera settings that will yield a satisfactory image. Therefore, film speed is part of a system that includes the color and intensity of the light on the subject, the subject itself, the type of light meter and the method of use, the film processing, the printing technique, and the criteria of image qualtiy."

From Photographic Sensitometry. "The concept of speed has become now one more closely related to practice, and we now do not consider speed as a fundamental concept. From the present point of view, any speed value (and there are many) is necessarily closely related to the application of the photographic material, and thus varies with the intended use."

Almost all film speeds are the reciprocal of the value of the exposure at a defined point based on a given criteria for a given film type multiplied by a constant. The criteria differs with the type of material and its intended use. Shadows play a critical roll in determining quality with black and white films, so film speed is determined in the shadows. Mid-tones are critical for reversal film. So the films require different testing methodologies; however, both use the same exposure meter and film speed scale. Speed points for black and white films and transparency films are determined at a difference of 1.0 log-H units. If a speed system was used that reflected the fundamental sensitivity of the materials, and if a black and white film had a film speed of 100, the transparency (with an ISO of 100), would have a speed of 1000. Black and white film speeds use a constant of 0.8 and transparencies use a constant of 10. This brings the speeds in line so they can both use the same meter and scale. Film speeds can only be effectively used in comparison with the film sensitivity of similar film types.

AgX · Nov 13, 2021

The OP's question so far got 45 replies, without further replies of the OP.

Thus we still do not know what he actually asked about.

Was it:
-) Why some people call the ISA or ASA "film speed"?
-) Why some people call the [it] "ISA" or "ASA" film speed?

Replies referred to either question.

grain elevator · Nov 13, 2021

How "speed" has come to mean the same as "sensitivity" has been explained now. I'm under the impression the OP wasn't quite aware that ISO or ASA is just the measurement and not the quality that is being measured. NBD and it's understandable because in a lot of places on the internet, a childish terminology seems to have taken hold. Being a bit of a grammar nazi, the practice of calling the speed "the film's ISO" or some such irks me. It's like calling one's weight ones "kilos" or "pounds" or "stones".

Stephen Benskin · Nov 13, 2021

AgX said:
The OP's question so far got 45 replies, without further replies of the OP.

Thus we still do not know what he actually asked about.

Was it:
-) Why some people call the ISA or ASA "film speed"?
-) Why some people call the [it] "ISA" or "ASA" film speed?

Replies referred to either question.

Referring back, I guess I was answering a question proposed by Chan Tran. It was more interesting.

Answer to OP: ASA and ISO refer to the standard which contains the testing methodology. ASA is the American Standards Associated, later changed to ANSI American National Standards Institute. ISO is The International Organization for Standardization. Placing the ASA or ISO prefix before a speed value indicates the film speed testing adhered to the conditions of the standard. Specifically the standards for black and white films are ANSI PH2.5 Method for determining speed of photographic negative materials (monochrome, continuous-tone) and ISO 6: Photography - Black-and-white pictorial still camera negative film/process systems - Determination of ISO speed. ISO has superseded ASA. Some still use ASA because they are old farts.

My personal pet peeve is when people use ISO when the correct term is EI, or when people use the term True Speed.

The history of film speed is actually rather interesting.

Chan Tran · Nov 13, 2021

AgX said:
The OP's question so far got 45 replies, without further replies of the OP.

Thus we still do not know what he actually asked about.

Was it:
-) Why some people call the ISA or ASA "film speed"?
-) Why some people call the [it] "ISA" or "ASA" film speed?

Replies referred to either question.

I am sure it's #1 and not #2.

Why some people call the ISO or ASA film speed

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