ISO variation with temperature. Is it important?

Simple question,

Looking at the Agfa Vista range they list:
Vista ISO 100/21 C
Vista ISO 200/24 C
Vista ISO 400/27 C
Vista ISO 800/30 C

Seldom to I photograph in temperatures a high as 10 C let along 30
Celcius ! Is it necessary (to ensure the best results) to account for
the temperature variation by assuming a lower ISO than stated, and
what would be the relationship between ISO and temperature?

If it isn't important, then why the big discrepency over the range of
Agfa films?

yours in puzzellment
Rachel

Rachel Koktava wrote:
Simple question,

Looking at the Agfa Vista range they list:
Vista ISO 100/21 C
Vista ISO 200/24 C
Vista ISO 400/27 C
Vista ISO 800/30 C

Seldom to I photograph in temperatures a high as 10 C let along 30
Celcius ! Is it necessary (to ensure the best results) to account for
the temperature variation by assuming a lower ISO than stated, and
what would be the relationship between ISO and temperature?

If it isn't important, then why the big discrepency over the range of
Agfa films?

yours in puzzellment
Rachel

If you're looking at what I'm looking at you're misreading it.

It's ISO 100 / 21 DIN
ISO 200 / 24 DIN
ISO 400 / 27 DIN
ISO 800 / 30 DIN

DIN is just a different way of expressing film speed. Don't worry
about it.

Nick

(Rachel Koktava) writes:

Simple question,

Looking at the Agfa Vista range they list:
Vista ISO 100/21 C
Vista ISO 200/24 C
Vista ISO 400/27 C
Vista ISO 800/30 C

The 21, 24, 27, and 30 should be followed by a 'degree symbol,' which
indicates not a temperature but a DIN number.

In the old scheme of things, Americans used ASA numbers and Europeans used
DIN numbers. ASA 100 is equivalent to 21 DIN, ASA 200 is 24 DIN.

Hope this helps.

--
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Legal Assistance on the Web | spam and read later. email to philip@
http://www.PhilipStripling.com/ | my domain is read daily.

"Rachel Koktava" wrote in message
m...
Simple question,

Looking at the Agfa Vista range they list:
Vista ISO 100/21 C
Vista ISO 200/24 C
Vista ISO 400/27 C
Vista ISO 800/30 C

Those aren't temperatures! I don't know what the C is for. There is
probably a degree sign. They are logarithmic (DIN-style) film speeds.

Thank you chaps, the puzzelment is dispelled. The "C" in my original
posting was 'ad libed' since a 'degree' symbol couldn't be typed. As
Agfa is a German country I guess it is natural for them to quote DIN
numbers and assume everyone knows what there are.

You live and learn

thanks again
Rachel

Rachel Koktava wrote:

Simple question,
=20
Looking at the Agfa Vista range they list:
Vista ISO 100/21 C
Vista ISO 200/24 C
Vista ISO 400/27 C
Vista ISO 800/30 C
=20


Those "temperatures" were the DIN way of expressing film sensitivity.=20
Note how every 3 "degrees" is a doubling in ISO? (eg: 1/3 stops of=20
sernsitivity)
(And the "C" was never used, it was simply degrees: =B0 - may not show u=
p=20
on your browser.)

When ASA was collapsed into ISO, likewise DIN sensitivity was erased as=20
a funny German idea that didn't stand the test of a good logical system. =

Most films still carry the deg. rating as there are many cameras with=20
DIN sensitivity settings still out there... (and for a long time yet).

In short, has nothing to do with ambient temp.

Cheers,
Alan

Rachel Koktava wrote:

Thank you chaps, the puzzelment is dispelled. The "C" in my original
posting was 'ad libed' since a 'degree' symbol couldn't be typed. As
Agfa is a German country I guess it is natural for them to quote DIN
numbers and assume everyone knows what there are.

Agfa is a German country? Hmmm. I learn something new every day.


You live and learn

It appears so!!

Alan Browne wrote:

When ASA was collapsed into ISO, likewise DIN sensitivity was erased as
a funny German idea that didn't stand the test of a good logical system.


Isn't ISO film speed rating really DIN? At least the measurement system.

Nick

Nick Zentena wrote:

Alan Browne wrote:

When ASA was collapsed into ISO, likewise DIN sensitivity was erased as
a funny German idea that didn't stand the test of a good logical system.



Isn't ISO film speed rating really DIN? At least the measurement system.

Nick

The ISO system is the IOS "world standardization" of the ASA system.
ASA (now ISO) is proportional to sensitivity. Double the ISO number =
double the sensitivity (1 stop of exposure). The mathematical "origin"
of the ISO scale is Exposure value of 0 (EV=0) at f/1.0 for 1 second on
ISO 100 film.

DIN is 1/3 stops per "degree", so it is exponential with a doubling in
sensitivity at every three degrees up... other than that... yes, they
are the same DIN 1 = ISO 1. (That's a "1").

Cheers,
Alan.

--
e-meil: there's no such thing as a FreeLunch.