Archived posting to the Leica Users Group, 1997/06/12
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]User Surachai V. at UNESCAP4 is not defined Original text follows ---------------------------------------------- Received: from gatekeeper5.un.org by mail-in.un.org (SMTPLINK V2.11.01) ; Thu, 12 Jun 97 03:54:33 EST Return-Path: <owner-leica-users@mejac.palo-alto.ca.us> Received: by gatekeeper5.un.org; id AA003441407; Thu, 12 Jun 1997 03:43:27 -0400 Received: from mejac.palo-alto.ca.us(192.147.236.1) by gatekeeper5.un.org via smap (V3.1) id xma029892; Thu, 12 Jun 97 03:38:11 -0400 Received: by mejac.palo-alto.ca.us id AA06525; Wed, 11 Jun 97 23:50:54 -0700 Received: by mejac.palo-alto.ca.us id AA06519; Wed, 11 Jun 97 23:50:51 -0700 Received: from pub (pub.brick.org [207.135.90.149]) by alink.net (8.8.5/8.7.3) with SMTP id XAA19132 for <leica-users@mejac.palo-alto.ca.us>; Wed, 11 Jun 1997 23:50:48 -0700 (PDT) Message-Id: <3.0.32.19970611234933.00bc77a0@pop.alink.net> X-Sender: jimbrick.brick.org@pop.alink.net X-Mailer: Windows Eudora Pro Version 3.0 (32) Date: Wed, 11 Jun 1997 23:49:36 -0700 To: leica-users@mejac.palo-alto.ca.us From: Jim Brick <jim@brick.org> Subject: Re: Noncoated filter Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: owner-leica-users@mejac.palo-alto.ca.us Precedence: bulk Reply-To: leica-users@mejac.palo-alto.ca.us At 10:42 PM 6/11/97 -0700, you wrote: >> >uncoated. Is it less important for a filter to >> >be coated than for a lens? >> >> Take it back. It will be the first surface to greet the incoming light >> rays. If it's uncoated, a lot of scattering, reflecting, and other ugly >> phenomenon will take place. >> >It seems to me that any light reflected from the first surface of the >filter will simply be reflected back to the subject and therefore not >degrade the picture. I can understand why the surface of the filter closest >to the lens benefits from coating. Am I missing something? > Yes, you are indeed missing something. The first surface is indeed the most important. I quote from Leica and B+W... "lens glass reflects about 4% of the incident light on each surface. It mirrors! This reduces light transmission, increases stray light flare, which superimposes itself on the true image, reducing contrast. In unfavorable situations (high contrast subject) this may cause double images of the bright areas. Surface coatings significantly reduce these damaging effects. This involves application of a layer of a special coating, such as magnesium fluoride, in a thickness of about one ten-thousandth of a millimeter on every glass-to-air surface. A single coating reduces the reflection on glass-to-air surfaces to 1.5%. Multicoating can reduce the glass-to-air reflections to 0.2%." Modern Leica lenses have a transmission of 99.8% A single uncoated filter will totally destroy this. If you use a filter, use the very best you can get. Multicoated if possible. There is no reason to purchase exquisite Leica lenses if they are going to be crippled by a layer of window glass. Jim