Archived posting to the Leica Users Group, 2000/05/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]- -- On Thu, 18 May 2000 19:06:17 Dennis Painter wrote: >Takeshi Hashimoto wrote: >> >> >> -- >> >> On Wed, 17 May 2000 19:15:36 Dennis Painter wrote: >> >Looking through the viewfinder Peter Niessen wrote: >> >> >> >> Dear all, >> >> >> >> today I noticed that, when using the series VIII yellow filter on my 4.8/280 >> >> Telyt, the infinity position had changed from infinity to a little >> >> above the 100m on the distance scale. The filter itself is approx 4mm >> >> thick. Is this result compatible with what others have observed? >> >> >> >> Cheers, Peter. >> > >> >Peter, >> > No, just the opposite. It moves the focus back (toward the film) by its own thickness, essentially by "delaying" the light as it passes through the glass. >> >I have pondered this off and on for a bit and cannot think of any way a >> >perfectly flat piece of glass would shift the focus. I think some others >> >mentioned that it will but don't think there was any real explanation of >> >how. >> > >> >Not specifically addressed here: >> > >> >http://www.schneideroptics.com/white/long.htm >> > >> >But they basically claim no effect. >> >> It does by moving the focus back the equivalent of its thickness. >> > >How does it do this? > >Does "moving the focus back" mean that it is as though the object 'seems >closer' by the thickness of the glass? Would not be much effect for an >object at infinity if that is the case. > >Again, how does it do this? > >Dennis > Get your FREE Email at http://mailcity.lycos.com Get your PERSONALIZED START PAGE at http://my.lycos.com