Archived posting to the Leica Users Group, 2007/10/26
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Hello Henning, Thank you for this explanation. I could not have done it better, maybe in Dutch...;-)) Kind regards Fred Hess ----- Original Message ----- From: "Henning Wulff" <henningw@archiphoto.com> To: "Leica Users Group" <lug@leica-users.org> Sent: Saturday, October 27, 2007 1:07 AM Subject: Re: [Leica] Question about A42 M Polarizer #13351 > >Hello Didier, > > > >To my documentation is a #13351 a A45 polfilter and a linear-type. > >The #13351 is a A42 push-on as well and also linear. > > > >May be can someone who's English is better than mine, explain what the > >difference is between circular and linear pol-filters. > >I can explain this perfect in Dutch.....but I think this would not help > >Didier at all. > > > >Kind regards > > > >Fred Hess. > > > > > > > > > >----- Original Message ----- > >From: "Didier Ludwig" <leica@screengang.com> > >To: "Leica Users Group" <lug@leica-users.org> > >Sent: Friday, October 26, 2007 1:05 PM > >Subject: Re: [Leica] Question about A42 M Polarizer #13351 > > > > > >> Fred an Hoppy, thanks a lot. > >> Hmmm, so far I believed a pol filter like this #13351 is a circular filter > >not a linear so don't ask me about the difference ;-) but I will be pleased > >to learn it. > >> Didier > >> > >> > >> >Its a liniar pol filter, the #13351 and you are correct: The filter is in > >> >the same pol-position in the 0 and 180-position. > >> >By the way: do you know the difference between circulair and liniar > >> >pol-filters?! > >> > > Right, it's a linear polarizer. The M's don't > need circular ones. The circular ones are for > cameras that use semi-silvered mirrors as part of > their operation, either for metering such as the > Leica reflexes or for AF. In those cases the > polarized light coming through the back of the > filter can interfere (cross-polarize) with the > polarization that occurs in the semi-silvered > mirror and a) cause overexposure or b) not AF > correctly or at all. > > The circular polarizer has a so-called 'quarter > wave plate' at the back, which depolarizes the > light again. That's OK, because it's the > relationship of the reflection of the light off > non-specular parts of your subject and the > polarization direction of the entrance of your > filter that causes the effect, and if it gets > de-polarized after that it doesn't matter to the > effect on the film or sensor. > > Circular polarizers are somewhat more expensive > to make, but don't create a better polarization > effect. > > As mentioned before, 0? is the same as 180?, for either type. > > > -- > * Henning J. Wulff > /|\ Wulff Photography & Design > /###\ mailto:henningw@archiphoto.com > |[ ]| http://www.archiphoto.com > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >