Archived posting to the Leica Users Group, 1997/03/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]"Peter Jon White" <pjwhite@tiac.net>: >Kari said, >> Linear works very simply as well. It is a unfortunate >>misconception that linear polarizer doesn't work with beam >>splitter meters. <snip> >While this may work in many situations, it can easily lead to >incorrect exposures. >For instance, while the polarizer has a neutral density of about a >stop, it affects polarized light far more than one stop. If the sky >is what you are darkening with the polarizer, you need to know it's >value through the polarizer in the position it will be in when the >image is made. Read my post and think the phenomenon at hand through. A meter with a beam splitter will always polarize the incoming light before it hits the silicon diode or CdS cell or whatever. Point the lens to the zenith at a clear day and rotate the camera to see this. So if your subject is throwing heavily polarized light at you, you must always be careful with a meter of this type. A polarizer at the "neutral" position (max as described previously), where it does not add any polarized wave directions, adds no further complication to the exposure determination. >In order to really know the effect the polarizer is having with this >type of camera, you must have a circular polarizer. Absolutely no. If you care about the physics, try it in practice. I've been shooting with a camera with beam splitter meter (Ftb, F-1s) for some twenty years. Polarizer used as I described works perfectly in *every situation* indoor or outdoor. If you can determine the exposure with a meter like that in the first place i.e. without the polarizer, with the method described you can do it with the polarizer as well. Some situations can be tricky *for the meter* and then it is better to bracket. The bottom line is that with a meter like that you need to be aware of the situations, where polarized light might fool you. The filter adds no complication. In your specific example the desired darkening of the sky usually amounts to more than one or two stops. But this is beside the point. You see the effect on the sky in the screen *after you've set the exposure*. The exposure reading you take from someone's face, some detail in the landscape etc., hopefully some non-polarized source. If you for some reason take it from the sky or some polarized source you need to worry just the same amount with or without the filter. >Peter Jon White Kari Eloranta