In the last week I had two light meters calibrated by Quality Light Metric in Hollywood, CA, a Pentax V analog spot meter and a Pentax Digital spot meter.
In an effort to protect my investment I thought I would put a UV filter on each meter.
The Pentax Digital takes a 40.5 mm and the Pentax V takes a 46 mm filter.
I metered the same spot on a target from the same position and the Digital meter is 1/3 stop lower than the analog. I can live with that as each meter was calibrated to manufactures original settings.
I added the UV filter to the analog meter and it metered 1/3 less than without the filter.
I added the UV filter to the digital meter and it metered 1/3 less that without the filter.
I am somewhat surprised as I always thought that a UV filter did not reduce the light passing through it and reaching the film.
As I thought about this I remembered from something I read long ago that light passing through any object no matter how transparent will always block some amount of light because light is made up of both a wave and a particle.
If I leave the filters on the light meters they will always show 1/3 less that with out the filter and I am wondering what effect this will have on my exposure.
Any thoughts on this?
Gary
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