Film speed question

[Galah]

Hi all!

I wonder if anyone out there can answer this question.

I have recently acquired a Zeiss Ikon Contaflex IV, with an "inbuilt" light meter (manufactured circa 1957).

The meter's setting dial (the 50+ years-old selenium cell lightmeter still functions:o)shows DIN film speeds with their corresponding ASA speeds.

However, there's something funny going on, because the dial shows the corresponding fiilm speed for 24 DIN to be 160 ASA (Should be 200 ASA/ISO, according to my understanding) and for 27 DIN, ASA 320 (instead of 400).

Can someone enlighten me as to what's going on? Did they change the DIN/ASA relativity at some stage? If so, which one is correct according to today's standard: the DIN, or the ASA/ISO?

Thanks.

[Q.G.]

You're understanding is correct. The meter is wrong. It happens.

[fdisilvestro]

I noticed that in an old camera I have. When I did some research I found that the ASA scale was changed around 1960. So I think that the scale you should use is the DIN, or ad 1/3 stop to the ASA.
Anyway, I would not trust a selenium cell lightmeter that old. You should test it.

[nickrapak]

When I use my Retina IIIc's light meter, I always use the DIN, as there used to be some sort of "safety factor" built into the ASA scale back then. I would also recommend testing the selenium cell against a known good light meter, as I have had some handheld meters be as much as 3 stops off, even though the meter seemed to work properly.