Re: BTFR question

[Clive Warren <Clive.Warren@xxxxxxxxxxxxx>]

At 7:38 pm +0800 28/4/00, Steve Hodges wrote:

>Clive Warren wrote:
>>
>> 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.
>
>Or reflected off it.
>
>Steve

Yep, good point.

Depending on the filter material and how the coating is carried out.  I
would bet that 95% of the light hitting the filter makes the trip through
to the film and the then 95% of the reflected light from the film makes it
back through the filter to the light sensors.

So it is only really around 5% drop in the reflected light to the light
meter sensors. This is not worth worrying about.  There may be a minute
anount of contrast reduction from internal reflections due to the presence
of the BTFR filter, again probably not detectable.

This is theory however and the only way to know for certain is to test :-)


All the best,

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


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