When did the industry move from ASA to ISO?

MattKing · Jun 30, 2022

The confusion arises because ISO, DIN and ASA are both - they are labels on the box and they are standards as well.
The standards coalesced in 1974, all under an official rubric of ISO certification.
But for a while, you could say the same thing in three different ways.
Sort of like six of one, half dozen of another, and 1/24 of a gross of a third.
And the choice of how to label something tended to vary with market and geography and producer- after 1974 you were much more likely to see ASA emphasized on the box of Kodak slide film, and DIN emphasized on a box of Agfa slide film. The DIN could usually be located on the Kodak box as well.
In or about 1982 the labelling started to coalesce as well. But it took some time for habits and practices to change.

AgX · Jun 30, 2022

ic-racer said:
Anyone know of a film in which the new ISO label was a different number from the old ASA number? I don’t know of any, but I’m only familiar with BW emulsions.

How could it be different? At the ISO designations the arithmetric part was taken over from the ASA standard.

BrianShaw · Jun 30, 2022

MattKing said:
The confusion arises because ISO, DIN and ASA are both - they are labels on the box and they are standards as well.
The standards coalesced in 1974, all under an official rubric of ISO certification.
But for a while, you could say the same thing in three different ways.

A bit of additional clarification: ANSI is the US standardization body; JIS is Japanese standardization body; DIN is Deutsch standardization body. National standards are developed, controlled, and updated by the respective national standards body. These standards may be similar or different, as we know these to have been.

ISO is the international standards body… a higher level of standardization. National standards are “elevated” to international standards for a variety of reasons and that process involves committee discussions and normalization. The goal is generally to satisfy all of the national needs. But there is often give-and-take. National standards are retired upon issuance of corresponding ISO standard. It’s a bookkeeping best practice.

Manufacturers may voluntarily CONFORM or COMPLY with the standards, and their conformance/compliance may be CERTIFIED independently.

Sirius Glass · Jun 30, 2022

faberryman said:
Beats me. Not sure when I noticed the letters changed. The numbers are the same. The film is the same. A non-event.

I noticed the change, but it was a non-event for me since I did not need to change the way I was doing things.

ic-racer · Jun 30, 2022

AgX said:
How could it be different? At the ISO designations the arithmetric part was taken over from the ASA standard.

The ISO document allows the film manufacturer to specify their own developer and development conditions. Different developers and development conditions can change the ISO. A manufacturer could could change a film from ASA 100 to ISO 125 with different development conditions.

5.4.2 Processing Specifications (ISO)

Eric Rose · Jun 30, 2022

They moved!!

AgX · Jul 1, 2022

ic-racer said:
The ISO document allows the film manufacturer to specify their own developer and development conditions. Different developers and development conditions can change the ISO. A manufacturer could could change a film from ASA 100 to ISO 125 with different development conditions.

To my understanding this was introduced in the ASA standard. But now you make me doubt.
Problem is that the ASA standard was continued after the introduction of the ISO, making it not easy to say for sure when which regulation was introduced where without having all standards issues at hand.

BrianShaw · Jul 1, 2022

Paul Verizzo said:
That I know. The question is "when?"

ISO Speed Standard for Film Speed

ISO speed is the standard for film speed, or film light sensitivity, used in ISO 6, ISO 5800, ISO 2240, and ISO 12232.

blog.ansi.org

Stephen Benskin · Jul 1, 2022

ASA PH2.5-1960 was an effort towards international agreement. The Fractional Gradient Method was too complicated and prone to experimental error for some. I believe only BS had adopted it. PH2.5 maintained the accuracy of the fractional gradient method as well as included the ease and repeatability of a fix density method through the use of the Delta-X Criterion. It also reduced a safety factor which adjusted the EI of film speeds by 2/3 to 1 stop. ISO 6:1974 is essentially the same as PH2.5-1960, or more precisely ANSI PH2.5-1972.

ISO 6:1993 made changes to better reflect actual use. The primary changes were to hold times, the elimination of the standard's developer in favor of actual commercial developers, and the method of development. It kept the Delta-X Criterion. From what I understand, the introduction of T-grain films was the motivation for the revision. Apparently the standard's developer produced speeds that didn't reflect the speeds that were produced with general purpose commercial developers. When T-Max 100 and 400 films were initially on the market, they only had EI speeds.

faberryman · Jul 1, 2022

I just googled up some film cartridges and boxes and I'm not sure they used the words ASA or ISO. The cartridges and boxes I looked at just had the number. Maybe that's why I was oblivious to the change. Perhaps someone could check their freezer.

Paul Howell · Jul 1, 2022

When did ISO show up on cameras? The F3P did not use ASA or ISO and as I recall the manual called it ASA/ISO. The F4 the film speed is set with a dial, it is labeled ISO.

ic-racer · Jul 1, 2022

Has anyone has posted a good spreadsheet to find the delta D. Since it is dependent on first finding the 0.1 point, you can't apriori know where the datapoint will be (to get it to fall exactly on a step of the stepwedge when doing the sensitometry exposure). Therefore, it will most likely fall between two points. Easy if drawing the graphs by hand. Also, didn't someone once offer to make some lucite "Speed Meter" overlays to place on the hand-drawn H&D curve?

My current spreadsheet is still a little lacking in Delta-X as it only automatically draws the single Delta-X condition of Delta D = 0.8.
In spite of what I wrote above, sometimes the Delta D is on a datapoint (red circle), as in the case below, but many times it is not, and therefore, would need mathematic interpolation.

Sirius Glass · Jul 1, 2022

Paul Howell said:
When did ISO show up on cameras? The F3P did not use ASA or ISO and as I recall the manual called it ASA/ISO. The F4 the film speed is set with a dial, it is labeled ISO.

If the dial increase by the square root of 2 ==> 1.4, it is ASA/ISO
If the dial is around 20 and increase or decrease by three, it is DIN

ic-racer · Jul 1, 2022

The Yashica FX-3 has ASA dial, whereas the FX-3 Super (1984) has ISO dial.

Kodachromeguy · Jul 1, 2022

Here is a data sheet for some "DEV BEFORE JAN 1974" GAF Versapan film that I tried in 2021:

https://worldofdecay.blogspot.com/2021/02/expired-film-treasure-135-size-gaf.html

Amazingly, the film was grainy but otherwise looked good (like a mid-century mid-speed film). Here is the first page of the data sheet, which shows the speed as ASA 125 / 22 DIN:

Paul Howell · Jul 1, 2022

In the 60s and 70s most film data sheets listed both ASA and DIN.

Kodachromeguy · Jul 1, 2022

Let's look at the Eastman Kodak 7th edition (1st printing 1958) of Kodak Films for Black and White Photography. It lists Panatomic-X as having an Exposure Index of 25 for daylight, 20 for tungsten. But they are to be used on meters marked for American Standard Exposure Indexes. But note the rather confusing statement that the indicated exposure measurement will result in negatives about two times the minuimum exposure needed. In another thread, we had a long give and take about when meters were changed to give the optimum exposure and not two times. Anyway, ASA and DIN numbers were not yet used in this book.

Stephen Benskin · Jul 2, 2022

Kodachromeguy said:
Let's look at the Eastman Kodak 7th edition (1st printing 1958) of Kodak Films for Black and White Photography. It lists Panatomic-X as having an Exposure Index of 25 for daylight, 20 for tungsten. But they are to be used on meters marked for American Standard Exposure Indexes. But note the rather confusing statement that the indicated exposure measurement will result in negatives about two times the minuimum exposure needed. In another thread, we had a long give and take about when meters were changed to give the optimum exposure and not two times. Anyway, ASA and DIN numbers were not yet used in this book.

View attachment 309471

That's because this is how the basic EI was derived. From the 1960 paper Safety Factors in Camera Exposure.

The implication is that the factional gradient speed is THE film speed. As the current ISO uses Delta-X, which is a method of finding the fractional gradient speed point using a fixed density method, where ΔX is always 0.297 log-H to the left of the 0.10 fix density point when ΔD = 0.80, it effectively makes the current ISO speed an EI.

The different EI ratings for daylight and tungsten is mostly due to the color temperature used in the calibration of exposure meters. Here is part of the abstract from the 1962 paper An Interpretation of Current Exposure Meter Technology.

AgX · Jul 2, 2022

Kodachromeguy said:
In another thread, we had a long give and take about when meters were changed to give the optimum exposure and not two times.

The standards, without emulsions changing, were modified, yielding films with twice nominal sensitivity.

in 1960 at ASA

in 1961 at DIN

in ???? at GOST (e.g. Wikipdia is contradictory on this in itself)

This lag already likely introduced confusion, let alone manufacturers not changingn over same time respetively different lots on sale in parallel.

Ian Grant · Jul 2, 2022

ic-racer said:
The ISO document allows the film manufacturer to specify their own developer and development conditions. Different developers and development conditions can change the ISO. A manufacturer could could change a film from ASA 100 to ISO 125 with different development conditions.

5.4.2 Processing Specifications (ISO)
View attachment 309413

The change in the ASA component of the ISO standard to allow the film manufacturers to specify their own developer was at the request of Eastman Kodak. Tmax 100 could not achieve 100 ASA in the specified ASA standard developer, by then Kodak were using a Phenidone (Dimezone) Ascorbic house developer for their in-house testing, PE - Ron Mowrey mentioned this in several posts.

Kodak were unable to market a developer like Xtol until the expiry of a Swedish company's US Patent covering a variety of Ascorbic based developers.
The current ISO allows films to be tested using either the ASA/BS standard or the DIN standard.

Ian

Ian Grant · Jul 2, 2022

Stephen Benskin said:
The different EI ratings for daylight and tungsten is mostly due to the color temperature used in the calibration of exposure meters. Here is part of the abstract from the 1962 paper An Interpretation of Current Exposure Meter Technology.

View attachment 309474

That makes no sense, it just means the meter is more accurate in daylight. It's only in quite recent years that manufacturers stopped listing both the Daylight and Tungsten films speeds.

Adox (Schleussner) used the Tungsten DIN speed to designate their emulsions, which continued when they were made by EFKE. later they renamed them with the Tungsten ASA speeds, so Kb14 became Kb25 (a slight improvement in the emulsion including better hardening), Kb21 became Kb100, the boxes and datasheet also listed the Daylight speeds.

Ilford used to give both the Daylight & Tungsten speeds for all their films, it was the rapid decline in use of Tungsten studio lighting that lead to the Tungsten speed no longer being listed. The exception is Ilford Ortho Plus, where both speeds are listed.

Ian

Stephen Benskin · Jul 2, 2022

Ian Grant said:
That makes no sense, it just means the meter is more accurate in daylight. It's only in quite recent years that manufacturers stopped listing both the Daylight and Tungsten films speeds.

Adox (Schleussner) used the Tungsten DIN speed to designate their emulsions, which continued when they were made by EFKE. later they renamed them with the Tungsten ASA speeds, so Kb14 became Kb25 (a slight improvement in the emulsion including better hardening), Kb21 became Kb100, the boxes and datasheet also listed the Daylight speeds.

Ilford used to give both the Daylight & Tungsten speeds for all their films, it was the rapid decline in use of Tungsten studio lighting that lead to the Tungsten speed no longer being listed. The exception is Ilford Ortho Plus, where both speeds are listed.

Ian

BrianShaw · Jul 2, 2022

Do we know, then and now, what meters are color biased red- vs blue-sensitive? Or is that a characteristic of the cell type: selenium v CDS v Selenium blue, etc? I’ve never noticed color sensitivity in the spec sheets (and never really noticed a difference in day-to-day use of 1960-2000 meters)

Stephen Benskin · Jul 2, 2022

r and p are variables in K. Below is a section from something I cobbled together a number of years ago.

BrianShaw · Jul 2, 2022

Thank you, Stephen!

When did the industry move from ASA to ISO?

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