Archived posting to the Leica Users Group, 1998/03/22
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Linear Polarizers: This works with a linear polarizer, but since the angle of the light can affect the amount of light passing through it and another polarizing layer (semi-silvered mirrors, et al.) they are not recommended for many cameras with off the film metering or where the light passes through the mirror, hits the shutter curtain and then is reflected to the floor of the mirror box where the light sensitive device can usually be found. Turning a circular polarizer will show minimal changes yet it does polarize the light to a certain and different way. Since there is no great change n light transmitted, regardless of angle of incidence, the sky doesn't get dark and the meter of most cameras with TTL and OTF metering doesn't shift readings as the filter is turned. The lights from glare and certain specular highlights is diminished, however, as this type of reflected light is polarized circularly. The sky light for all practical purposes, in passing though the atmosphere, is passing through a LARGE linearly polarized filter- about 200 km of atmosphere. Incident light seems to be polarized linearly if at all, and reflected light is polarized circularly. This was somewhat how a physicist explained it to me, only he did a better job! Do a few tests around water, glass, and shiny bald heads! You will see a difference! dwpost@msn.com - -----Original Message----- From: Tina Manley <images@InfoAve.Net> To: leica-users@mejac.palo-alto.ca.us <leica-users@mejac.palo-alto.ca.us> Date: Sunday, March 22, 1998 8:29 PM Subject: Re: [Leica] use of circular polarizer >At 02:27 PM 3/22/98 -0500, you wrote: >>i could use some advice /clarification. >>having never used a circ.polarizer, i recently obtained one for use with a >>180/3.4 >>apo lens on my R8. >>i have always thought that by turning this filter one would obtain different >>density at different settings. it seems that my P-cir 13406 has an even >>density across the entire filter even though the glass element can be >>turned. >>are my eyes getting bad ? If not, why can the glass be turned when the >>entire glass has the same density /shading of grey ? >>thanks for any advice. >>hans >> > >Hans - > >The extent that light is polarized depends on the angle of the light. You >will have to look through the filter with the light coming in at an angle. >That's why polarizing filters have more of an effect when the sun is low in >the sky. Take the filter outside on a sunny day and look at the sky >through it from different angles. As you turn the filter, you will see the >sky darken when the light is most polarized. Hope this helps. Tina > > >______________________________________________________________________ > >Tina Manley, ASMP ><http://www.photogs.com/manley/index.html> ><http://www.aperture-photo.com/site/reportage/manley/manleyframeset.html> ><http://www.onlineartistleague.com/manleyt/portfoli.htm>