[LRFlex] Re: Filters, screw in can of worm?

Kent,

I appreciate your quote. It is quite explicit. And it explain why with a summicron 35mm or longer focal there is not any strange behavior.

Hmmm, Then I should remove the filter in front of the 24mm elamit. It bothers me as this fiter serves as a protector.

Cheers.
---------------------------------
Xavier F. BILLE
Maisons-Alfort - France.





From: Kent Christensen <lkchris@xxxxxxxxxxxxx>
Reply-To: leicareflex@xxxxxxxxxxxxx
To: leica_reflex_forum <LeicaReflex@xxxxxxxxxxxxx>
Subject: [LRFlex] Re: Filters, screw in can of worm?
Date: Tue, 27 Jul 2004 10:17:29 -0600

re: ... wonder if it is not related to the use of a [UVa] filter in some cases of light. Could it be something to do with the formula of the lens which cannot cope with an extra glass in front of the lens? Any comment? (Xavier)


A direct quote from Leica's Summer 1983 publication "Leica R-Lenses: meet all needs in any situation for any application:"

"LEICA lenses of the current generation (from about 1965 onwards) absorb ultraviolet rays through the use of certain types of glass and above all through a certain method of cementing the lenses, so that basically a separate UVa filter is unnecessary. ... The UVa filter on Leica R lenses today therefore merely serves as a protection for the front element of the lens.

It must, however, be mentioned here that even high-quality filters may create problems in certain situations. At high contrast, for instance during sunsets, in night shots including powerful light sources in the picture and when bright objects are photographed through a dark arch, the risk of reflections even from optically flat and coated filters is very great. Double images or a general degradation of the contrast or partial lightening through stray light are relatively frequent. In such photographic situations all filters, including the UVa filter, should be removed. With ultra-wide angle lenses, too, filters may lead to inferior photographic results. Owing to the wider angle of field the marginal light rays must traverse a slightly longer path through the filter in front of such lenses than the light rays in the centre. This may often adversely affect the picture quality, and is one reason why, for instance, no filter is offered for the 19mm ELMARIT-R f/2.8 lens.

Skylight and haze filters

These slightly tinted UVa filters were in the past recommended for colour photographs of subjects with exceptionally high UV and blue content of the light, such as subjects in the shade or distant views through slightly blue haze. Their use with the current LEICA R lenses is discouraged, because they will make the colour rendering unnaturally warm."

Kent Christensen
Albuquerque, NM, USA

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