Re: BTFR question

[Clive Warren <Clive.Warren@xxxxxxxxxxxxx>]

At 11:04 am -0700 27/4/00, Patrick Magee wrote:

>Does it meter with the shutter open? That is the only time there would be
>a "problem".
>
>On Thu, 27 Apr 2000, ADavidhazy wrote:
>
>> While it may pass through the filter twice it does not matter anyway because
>> you have to determine proper speed index to set meter to in any case.
>>
>> Andrew  o o  0 0 o . o  Davidhazy, Imaging and Photo Tech
>>          \/\/\/\/\/\/          http://www.rit.edu/~andpph
>> __________|        |_____________________________________
>>
>> > I have a question regarding the between the film rails placement of the
>> > IR filter. Don't TTL metering systems measure the light reflecting off
>> > the film plane (OTF)? If so, wouldn't the meter reading be different
>> > with the filter placed between the rails as opposed to in front of the
>> > lens because the light would then pass through the filter twice? Or, am
>> > I wrong, and the camera's meter does not read light reflected off the
>> > film plane?

Most Olympus cameras meter Off The Film (OTF) TTL with the shutter open in
their aperture priority "auto" mode.  This would indeed result in the
metered light passing through the filter twice.

Guess that most of use would be using similar cameras set to "manual" for
IR work.  However, as Andy points out, a test roll of film with some
bracketing is the best method to calibrate any camera/meter combination for
your own preferred results.


All the best,

             Clive   http://www.cocam.co.uk
                     Photographic Services, Filters and Equipment, Infrared FAQ


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