Us old guys will ask 'ISO?'.

The kids will ask 'FILM speed?'.

Sunny 16 rule meant f/16 with shutter at 1/film speed.

In common use ASA. and now ISO, is a number that tells you the light sensitivity of the film or sensor, as you intend to process after the exposure. Back in the good old days before all cameras had light meters, you had to measure the light and set the camera, and maybe share your readings with someone else, either to compare or so they could set their exposure.

And as many of us learned it, ASA was a number the represented the needed shutter speed to properly expose the film on a bright sunny day with the lens set to f16. It was very common to dig out your meter, take a reading with the meter set to the film you are using, and find was an "f8 and 125" day, just like so many other days. Changing the shutter and aperture step for step to keep the same exposure also yields f11 and 1/64, and f16 and 1/30. You could use any of the three, or others of course, but f8 and 125 gives a good lens setting, and shutter speed fast enough that you can easily hand hold the common 50mm lens.

And I imagine that those that were shooting like this back then will recognize the film; it was Kodachrome 25. The 1/30th second shutter speed at f16 and bright day tells you that.

ASA (American Standards Association) has been around since the early 20th century. It changed its name to ANSI (American National Standards Institute) in 1969. One of the many ASA standards was the way to measure film sensitivity. This standard was taken over in its entirety by ISO, which is the world standards organization. ASA was a founding member of ISO in 1947. Today, 153 countries belong to ISO. When ISO adopted the ASA standard, and ASA lost its name, the scale became known as the ISO scale. It is one and the same - but it was never re-named into ANSI-scale.

This is all quite humorous. Using the term ASA certainly dates us like "ethyl" grade gasoline, "record stores", or "stereos", but saying "I would like to buy some 400 ASA film" is kind of a badge of honor.

But getting back of the original question ISO vs ASA as well as DIN. They are all measures of film or digital sensor sensitivity defined by different organizations and ISO speed is equal to ASA speed.

I was taught ASA but also known as ISO. From the start back in 2008

because ASA is the American Standards Assoc. and that just won't do these days for international branding.

I remember ASA and wondered why Iso took over... I guess the International Organization for Standardization won the bid...

Yes, Chris, I know :^)

Actually the ASA dial on my F2 only goes to 6400. I said it goes to 12800 because there is a marking for -1 (and actually -2, except the dial doesn't spin all the way) exposure compensation. Like you said, changing ASA doesn't change anything with the film, it just changed the image that ends up on the film (assuming you always read off perfect exposure), which in developing you have to push or pull to compensate for.

Pushing doesn't even have to involve the light meter really, or ASA setting. There's a conception that changing an ASA is changing film speed or something, all you're doing is telling the meter to read something at a higher or lesser sensitivity. Most films aren't even specified as a certain ASA, they're really guide lines, and your 'effective' film speed will be something a bit different. I for instance, always process Fuji Neopan SS 100 for 7 minutes in straight D76, even though the box says 6:45 for 100 and 7:15 for EI 200. This results in slightly higher contrast, and a more punchy negative, to my taste, at an exposure index of 100. However, If I were to rate the film at 80, and process for 6:45, I would basically be achieving the same exposure value, but the results would look quite different, with less contrast and more even tones.

I guess it comes from digital cameras where you're actually increasing the gain level of the sensor when you increase the ISO setting that people have this misconception that your light meter changes your film. Film reacts uniformly to light no matter what your meter is set to. If you have a 100 speed film and you're rating it at 50, you're giving the emulsion a stop more light than its nominal rating, and from there you can decide whether to process for less time and actually "pull" the film, or if you will keep the same development time for 100 and achieve a lighter negative that you can alter later on in the printing process.

Were you to do this with a digital sensor, you would just have a one stop over-exposed image.

Film speeds are really calibrations of certain contrast indexes, or "CI"s. If you push, you're increasing the CI, and if you pull you're decreasing the CI, while maintaining the same over all exposure value. This is why some people's 'normal' rating for Tri-X 400 is always 640, or always 320, depending on their own variables in processing. Some people always cut their ASAs in half and maintain the same development times (this isn't pulling, just developing to a higher contrast) for softer tonal variations. My father used to shoot certain color films like Portra 400 at an EI of 6 for fashion covers or glamour stuff (yeah, six) and have it processed normally, resulting in ultra smooth high lights and great tonal seperation. Obviously that's an extreme example, but the principals are the same.

My personal speeds for Tri-X tend to be 320 for TX400, and 250 for TX320, for example. I expose Efke KB25 or R25 at 12 often times to really capture a full range of tonal values, and then I print with a higher grade paper or filter later on to bring some punch back in.

Metering for ASA is really just another venue for exposure compensation.

I'm just an ISO guy (being 13—hey, am I the youngest person on the forum?), never knew about anything else really. From the time I spent with ASA I had no idea what it was anyway. When I was using my F2 Photomic to learn about the basics of photography, ASA wasn't a factor to me. All my films were the exact same, so I just set it to the big "400" I saw on the film, and forgot about it. On a side note, my F2 does go to ASA12800, I suppose in case I ever want to push anything...

ChrisLange said:
I also rarely say things like f/9 or f/7.3 or whatever the interim stops are, I'm a "sixteen five" or "eight and a third" kinda guy.

Who bothers with those anyway? They're impossible to remember, your "eight and a third" method is much better :^D

I wasn't around for DIN, being only 19, but I do habitually say ASA instead of ISO. My father is a photographer, so I've adopted a lot of his habits in terms of how I treat my gear and all that, so since he grew up saying ASA, so do I. I also rarely say things like f/9 or f/7.3 or whatever the interim stops are, I'm a "sixteen five" or "eight and a third" kinda guy.

how about saying "chromes" instead of slides?

Nik V - Looks like you win the prize. You outrank me by about 15 years.

astrophotographer said:
Now how many here know what DIN was?

getting old too :) as I still remember that

nikyvee said:
Now I know I am REALLY old. When I first started with cameras, there wasn't any ISO OR ASA OR DIN. It was just an old Brownie box camera. AND, a pinhole camera made in my boyscout daze.

Am I really the oldest person on this forum, at age 70?

Nick V "with the little bit of gray hair to prove it..."

nick, I'm more than half Your age, and have some gray hair here and there :)

ChrisLange said:
There's Kodak TMZ3200 and Ilford Delta 3200...

High end stuff no doubt. Back in the film days we shot with Kodak Gold from the drug store.

Now I know I am REALLY old. When I first started with cameras, there wasn't any ISO OR ASA OR DIN. It was just an old Brownie box camera. AND, a pinhole camera made in my boyscout daze.

Am I really the oldest person on this forum, at age 70?

Nick V "with the little bit of gray hair to prove it..."

There's Kodak TMZ3200 and Ilford Delta 3200...

Ah, I just assumed it stopped, since I never saw film rated over ASA 1600.

ASA is strictly the 1/2/4/6/8/12/25/32/50/64/80/100/125/160/200/250/320/400/640/800/1000/1250/1600, etc scale, whereas ISO incorporates both the "degree" designation of the film as well as the traditional ASA designation.

ASA is pretty much analagous to ISO since we really only look at the first part of an ISO designation in most situations (find me one person who actually buys film primarily based on what degree or DIN it is...), and so the terms are interchangeable.

My F3 has ASA settings up to 6400, it didn't just 'stop' at 1600...it goes all the way up to infinity basically; while practically ending at 25600 since I don't think anyone ever pushes film any further than that.

I think that this is what DIN means: DIN speed:

Film speed system used by German standards organization. It is based on a logarithmic scale and is represented by a number printed on the film carton or box. A change of +30 in rating indicates a doubling of film speed, e.g. 210 DIN is twice as fast as 180 DIN and 150 DIN half the speed of 180 DIN. The system has now been replaced by the ISO system.

soap said:
Did you read the link?

Excuse me soap, I missed that. Let me read it...

When I started in photography is was ASA. I'm feeling old.

Now how many here know what DIN was?

alphanikonrex said:
So then what I don't understand is why ASA became ISO? I mean, what does it have to do with anything?

Did you read the link?

Thanks PB PM. That IIRC was a FAIL on my part though *facepalm*

So then what I don't understand is why ASA became ISO? I mean, what does it have to do with anything?

BTW ASA stands for American Standards Association, which later became the American National Standards Institute. Later camera companies and film makers switched to the International Organization for Standards (ISO).

ASA only went to 1600, because ASA1600 was the fastest film made.

Sorry, IIRC = If I Recall Correctly.