Re: Autoexposure Follies? (was Re: Nikon Data Backs

[Joshua_Putnam <josh@xxxxxxxxxxxx>]

pico <pico@xxxxxxxxxxxxxxxxxxxx> writes:

>All this talk about the difficulty of using a modern, highly
>advanced camera for IR seems to indicate that it's simply not a
>good choice, and perhaps a totally manual, nonelectric, simple
>camera would be best. Perhaps an old Nikon F, Leica M, Olympus,
>Koni-Omega 6x7, etc...
>
>This _assumes_ that integrated meters cannot really be set
>properly for IR work. 

While I'll still bracket under difficult conditions, or for
shots that would be hard to re-take if the first try doesn't
work, I actually get fairly good exposures for both HIE and
Konica using auto-exposure on my OM-2 and OM-4, metering through
a no.25 filter in bright to fairly hazy conditions.  The
exposures may not be absolutely perfect, but I get only one or
two really useless negatives per roll.  (Of course, that's
partly because HIE gives interesting effects over a wide range
of exposures, so I may end up with a useful negative that isn't
what I was planning on.)  I just set the film speed dial to 400
and shoot.

Usually the really useless negatives are with HIE, from subjects
that are dramatically more reflective in IR than deep visible
red.  The slag heap of a local copper smelter comes to mind --
in visible light the rock appears dark brown, almost black, but
it's almost as bright as tree bark in IR.  Where the tide ranges
over it, it's covered by a dark slimy seaweed that is also
fairly bright in IR.  Anything shot auto-exposed at 400 against
that background will give a negative so dense you'd think the
film had been directly exposed to daylight.  

With an 87 over the lens, my OM-4 does get something registering
on the meter, but I haven't taken the time to attempt to get a
good film speed setting for auto exposure.  (The meter on the
OM-4 is separately lit from the viewfinder, unlike the OM-2, so
it is possible to see what reading it's getting even though the
viewfinder is completely black with the 87 in place.)

I have not tried any auto-exposure using the between-the-rails
filter -- I assume the auto exposure would vary wildly since the
meter would be seeing all the light, not just what gets through
the filter.  (Besides, right now I have the between-the-rails
filter on my OM-1, so auto anything isn't an option.)

- -- 

 Josh@xxxxxxxxxxxx  is  Joshua Putnam / P.O. Box 13220 / Burton, WA 98013
                       "My other bike is a car."                   
                     http://www.wolfenet.com/~josh/
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