Reciprocity failure was: Re: How can I recognice 'old' Ektachrome IR?

[Helmut Faugel TE <htf@xxxxxxxxxxxxxxxxxxx>]

On Sun, 30 Mar 1997, Gord Jeoffroy wrote:

> At 11:25 26/03/97 GMT, Helmut Faugel TE wrote:
> 
> >But a reciprocity failure of 1 stop at 1/10s is very limiting for low
> >light subjects.
> 
> In general I'd agree, but how many people shoot IR -- especially
> colour IR -- in low light situations?

Is 1/10 s a low light situation, I'm not sure ...

For example on my trusty Canon EF 2.0/35 the IR-mark is on the half way
between focus and the DOF-mark for f/11, so it's equal to a f/5.6 mark.

To get a sharp picture I can do the following, stop down to f/5.6 
with no focus shift, or shift the focus between normal focusing mark
and IR-mark and stop down to f/2.8 . With both settings the slides will
not turn out very sharp so I would add two stops. Assuming a speed of
ISO 80/20 with a Wratten #16, f/11 and 1/10 s the scene is about five
stops darker as we know from the 'Sunny 16', not a typical low light
situation, looks like bad weather.


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