Topic: ASA radically changed in 1960???

[mcduff]

I read this in the Wikipedia today and I have seen it parroted across the web. It states that the criteria for measuring ASA radically changed in 1960 when the old "ASA PH2.5-1954" standard was replaced with ASA PH2.5-1960 which effectively doubled film speeds! Now this really does not effect me much as almost everything I shoot is post-1960. But this is kind of mind blowing. It it is true and you used a pre-1960 light metre (ok highly unlikely) you could be off by a stop! It is like finding out the moon landings were really fake!!!

Has anyone else heard of this?

http://en.m.wikipedia.org/wiki/Film_speed#ASA

"when the method to determine film speed was refined and previously applied safety factors against under-exposure were abandoned, effectively doubling the nominal speed of many black-and-white negative films. For example, an Ilford HP3 that had been rated at 200 ASA before 1960 was labeled 400 ASA afterwards without any change to the emulsion. Similar changes were applied to the DIN system with DIN 4512:1961-10 and the BS system with BS 1380:1963 in the following years."

[Mike Crawford]

My Rollieflex 2.8 E is dated at 1959 according to the serial number and the selenium light meter is still very accurate giving well exposed negs at normal, contemporary ASA/ISO ratings. Well it is when
outside, never been that reliable in low light conditions!

[Francois]

It actually probably doesn't affect meters since, as they say, the speed change was to eliminate a safety margin applied to films.
For the safety margin to be effective, meters must not correct for it in any way.

But that could explain why the ads for old films always show such low ASA ratings. So an old film rated 50 ASA was in reality a 100 ASA film with a one stop safety... clever.

And for now, that doesn't mean didley since those films have lost pretty much all their sensitivity by this time.

[ManuelL]

So when you shoot a film with the old ASA rating on a camera with the old Ross Grundlach F-stop rating, you would use the same shutter speed as on a camera with the new f-stop system and new ASA rating? 

[Late Developer]

Not sure how much this will add, in terms of clarification, to the original question, however....

In the last couple of years, I've often found that I like the results more when I halve the box speed of print film (definitely not slide film).  For 400 ISO (which I use most commonly), Ive experimented with setting the camera's or my hand-held meter's ISO setting to 320, 250 and even 200. 

I've recently read articles which show the results from colour print film over-exposed by up to 4 stops - with minimal detrimental impact other than colour shifts.  Under-exposure provided much less tolerance with two stops being the point at which the image quality became seriously compromised.

It may be that the box speed shown is little more than a "guide" as to the ISO the film can be used in "normal" daylight situations.  Yesterday, as an experiment (to see if it reduces contrast) I shot a roll of 120 XP2 Super rated at 200 ISO in very grey / drab conditions and I'll post the results when I get it processed in the New Year.

[mcduff]

Ya Francois, perhaps it does help explain when 50 Asa was referred to as "high speed film"

[mcduff]

LD, there are a few films that are often shot slower than rated box speed (without modifying processing time), maybe the old rating was more accurate

I wonder if it was partly marketing-driven?

[Late Developer]

LD, there are a few films that are often shot slower than rated box speed (without modifying processing time), maybe the old rating was more accurate

I wonder if it was partly marketing-driven?

That sounds about right. 

I started shooting in early 1970's and I was convinced there was something a bit wrong when the DX coding came in as the results were never quite the same as when I'd rated lower, manually.  It's only recently, after reading a random article, that I've started to play with ISO settings and I'm starting to like shooting "quick" film a little bit slower.

[Francois]

When you read Ansel's The Negative, he is very clear about the fact that the box speed is just a recommendation by the manufaturer. But I drop the ball at the point where he describes all the testing required to figure out your personal iso...

Underexposing does allow you to capture a wider contrast range when shooting in contrasty situations.

[mcduff]

All this talk about film speed (here and with the ISO 320 HP5) makes me think of good old Delta 3200, which I used to think was an ISO 1600 film. But I just read Ilford says that technically it is an 1000 film:
"DELTA 3200 Professional has an ISO speed rating
of ISO 1000/31º (1000ASA, 31DIN) to daylight.... It should be noted that the exposure index (EI) range recommended for DELTA 3200 Professional is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard."

[imagesfrugales]

the exposure index (EI) range recommended for DELTA 3200 Professional is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard."

And that's a good recommendation imo. If you apply the zone system (foot speed) on this film you will get strange results with available light e.g.. Assumed you choose a developer who doesn't cut film speed you will get great results at 3200 or even more. The film is not "forgiving" but very low in contrast and benefits from a contrasty (speed increasing) development. Btw, I mostly prefer practical evaluation over abstract ratings. If you get the results you want, there's nothing to say against underrating a film and vice versa. The zone systems is a good help for me to understand the whole thing but I don't apply it on my ordinary photography. Especially since I mostly use speed increasing developers (Caffenol-C, diluted Xtol) and/or techniques (stand development). I would probably prefer an ISO 100 film @ 200 over an ISO 400 film @ 200. The 1960s ASA change is of no real meaning for me and today.

There's an old photographers say about exposure: if in doubt, add one stop. Before 1960, all films had that stop built in because of the lower speed rating.