Re: Focus rules of thumb (EIR)

[Eckhard Stephan <eckhard.stephan@xxxxxxxx>]

Sarah Morgan wrote:
> 
> What are the general rules of thumb when adjusting focus and exposure to go
> from regular color film to IR film (EIR 135-36 exp).  

EIR doesn't require any focus corrections. Just focus like with any
"normal" film.

> Is there a difference
> in the angle the wavelengths of light strike the film in visible v. IR
> range?  How critical is the exposure.  These questions are for shooting
> around 10 foot away from subject (not aerial shots).
 
Bad news first: Exposure IS somewhat critical. You only have a mistake
tolerance of about +/- 0.5 aperture stops, if you want that perfect
picture. Not too much...
Good news: Once you have established a filter-exposure combination that
works well for you, a bracket of +/- 0.5 aperture stops around the
metered value will give you at least one good pic in almost every
situation. If only HIE was so easy to handle...
As usual: "Your first roll should be a test roll" - even if EIR is very
expensive...
Try some shots under different lighting conditions with a bracket of at
least +/- 1 aperture stops in steps of 0.5 stops and find out, which
film speed setting gives you the results you like best. Of course it
would be a good idea to take some notes :-)

Starting points (meter setting) for your tests (development in standard
E-6 process):

Yellow filter: ISO 250 (TTL, through the filter, integral metering)
Orange filter: ISO 320 (dito)

You may also want to try a Wratten #25 red filter at ISO 400 and see, if
you like the look. It's not everybody's cup of tea...

Please keep in mind, that these suggestions are only a starting point.
Depending on your light meter and your personal taste, you may well
arrive at slightly different figures. It's also very likely, that other
people on this list would recommend other film speed settings. ;-)

> What filtration effects does an overcast day have v. a sunny day or partly
> cloudy day.  What setting must you change for each circumstance?

Personally, I use the same film speed setting and the same filters
(yellow, orange or red) on sunny and cloudy days. But I haven't done too
much EIR shots on overcast days yet...

Happy shooting,

Eckhard


-- 
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*          Eckhard Stephan             * 
*          Freiburg (Germany)          *
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