Re: ASA/ISO use

["Willem-Jan Markerink" <w.j.markerink@xxxxx>]

On  2 Aug 96 at 19:34, kenneth.r.rockwell@xxxxxxxxxx wrote:

> When one speaks of ASA or ISO on 35mm format with a filter is one setting 
> that value on the camera for through-the-lens reading, or is this the value 
> set using an external meter with no filter?

Mostly, if not always, this refers to an external meter reading,
*or* a no-filter reading. The problem with trough-the-filter
readings and onboard camera meters is that most modern cameras are
highly insensitive to IR; not by nature, but due to IR-block filters
to keep AF and AE readings 'clean'. 

As an illustration, below the recommended camera settings for
Konica/Kodak, taken with the Heliopan RG 715 filter (equals Wratten
88A, almost opaque to the eye, only faint contours of trees and
buildings visible):
[extracted from FotoMagazin 8/95, as a result of various IR 
workshops] 


[A] Konica 160 ASA & Kodak 800 ASA for:
-Canon AE-1/A-1
-Minolta X 300/500/700
-Olympus OM
-Nikon F-301/FA/F3
-Pentax Super A/LX

[B] Konica 250 ASA & Kodak 1250 ASA for:
-Canon T80
-Olympus OM-30
-Pentax ME Super F
-Nikon F3 AF

[C] Konica 400 ASA & Kocak 2000 ASA for:
-Canon EOS
-Minolta Dynax/AF
-Nikon F801/F50/F70/F90/F4 (the latter with evaluative & matrix 
-metering)

 
The general rule is: the younger the camera, the less sensitive to 
IR. 

As for external meters, they are much better in this through-the-lens 
reading stuff....my Gossen Sixtomat Digital shows rather accurate 
readings, it doesn't 'black out' like internal meters do.
Note further that any no-filter reading is dangerous, since the 
relative amount of IR changes; early in the morning and late in the 
afternoon, the relative amount of IR is twice as much as at noon. So 
even though the no-filter reading shows more light at noon, there is 
less IR! I think this is closely related to the fact that UV is at 
its peak at noon, so the relative amount of IR *must* be less at that 
time.

 

 
 
--
Bye,

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The difference 
between men and boys
is the price of their toys

<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]

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Topic No. 4