Re: [Leica] Noctilux and filters

[Ken Iisaka <kiisaka@pacbell.net>]

Joe B. wrote:
> What I am curious about is exactly why Leica recommend (I can't
remember
> exactly where I read this) that filters not be used with the Noctilux.
They
> don't say this about most of the other Leica lenses, and I wonder what
the
> distinction is. I have used filters with the Noctilux in situations
where
> it was the only thing to do, like for example with Infrared
Ektachrome. I
> didn't get many correctly focused shots that time, and I wonder if
possibly
> the filter affects the focus accuracy with such a wide aperture lens.
On an
> SLR with TTL focusing I don't think it wouldn't be an issue, but with
a
> rangefinder it might be. I wonder if anyone who knows about filters
and
> focusing errors could comment on this.

My take on this issue is that Noctilux, when used in situations for
which it was designed, would often encounter bright light sources in the
background.  If a filter is used, it may cause ghosting which may become
visible because of these light sources may be many EVs brighter.  You
would not encounter such high contrast in most situations.

I cannot verify this, however, as I neither do or plan to purchase a
filter for my Noctilux and Summilux 75mm.