[Jorgario]

I have an old spot meter that I really like it, but I do not know if the film ASA mesures are the same as the digital ISO sistema ?

[boriscleto]

The ISO scale and ASA scale are the same.

[Jorgario]

Thanks for your promp answer !!

[Douglas_of_Sweden]

I always preferred the DIN scale...

[hcarvalhoalves]

Just notice that there are two different scales for the ISO standard: linear (e.g.: ISO 100) and logarithmic (e.g.: ISO 21°). The linear is equivalent to the old ASA, while the log is equivalent to DIN.

[Barry Pearson]

I always preferred the DIN scale...

I started with the Hurter and Driffield scale!

(In the UK, we tended to use the BSI rather than DIN scale: just add 10).

[Kerrowdown]

ISO and old ASA are the same

Aye the same, ASA is for auld buggers like me, ISO is the new fangled way for the young folk.

[JimJohnson]

There is a difference between ASA and ISO, but....

According to wikipedia (it must be correct, it's on the Internet, right?) ASA (American Standards Association - Kodak had a major impact on this standard) was first defined in 1943 and went through several modifications. The last modification was in 1960. ISO (International Standards Organization) basically adopted both ASA and DIN as standards in 1974.

ISO exposure values have also witnessed several changes since 1974. It appears the latest change was in 2006. There is a minor impact on digital photographers using both older and newer camera bodies as older bodies without post-2006 firmware updates will be using an older exposure calculation.

And as kerrowdown says- for us "auld buggers like me", I still use light meters manufactured in the 60's and 70's when 'digital' meant you were counting on your fingers. For my photography the difference between the 1960 standard for ASA and the 2006 standard for ISO is meaningless. This is because it is well within the dynamic range of my camera's sensor and for most photography exposure is an artistic choice achieved in post processing. I doubt Ansel Adams would have worried about the difference either.

[Dan]

I like this sentence from the Wikipedia article about the revised standards:

"Despite these detailed standard definitions, cameras typically do not clearly indicate whether the user 'ISO' setting refers to the noise-based speed, saturation-based speed, or the specified output sensitivity, or even some made-up number for marketing purposes."

Well that explains a lot!!

I find that most digital cameras have rather "optimistic" ISO ratings in comparison with old-school metrics such as the "sunny f/16" rule.

Dan

[RKKS08]

"Despite these detailed standard definitions, cameras typically do not clearly indicate whether the user 'ISO' setting refers to the noise-based speed, saturation-based speed, or the specified output sensitivity, or even some made-up number for marketing purposes."

Standards like ISO are internationally agreed on, but will be followed only if commercally accepted.

You know there is, since decades, an internationally accepted ISO standard for electrical plug systems?
As far as I know, just two or three 3rd world countries have officially introduced it. But as they are flooded with devices built in the industrialized world, it hasn't really changed reality.
Each country is still fencing its own market to protect its industry.

I guess if the success of SLR against RF cameras of Japanese companies hadn't destroyed most of the German (and European) camera industry in the sixties/seventies, we would still use "°Scheiner/DIN" in my country (DIN translated means "German Industrial Standard").

EDIT:
I also remember there existed (or exists?) an ISO standard that wants cameras to accept flash trigger voltages up to 24/25V.
But there were user reports about one Canon P&S which gets fried by trigger voltages of 6-7V.
And Canon was a member of the making body who discussed and decided about just this standard!