Archived posting to the Leica Users Group, 2003/05/18
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Looking at the pictures I think that there is more at play here than I first
thought.
I think that the lens must have a fault in either the centering of one or
more elements or a fault with the aperture blades.(slow or sticking).It is
not a shutter fault as this would cause uneven exposure in vertical bands
across the frame as the M shutter is a horizontal run type.
If it was my lens I would return it in exchange for another one.
Hope this helps.
Regards,
Mark.
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- ----- Original Message -----
From: "Y. Li" <liyue@netvigator.com>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Sunday, May 18, 2003 8:45 PM
Subject: Re: [Leica] Vignetting of Summicron M 2/28mm ASPH
> Hi everybody on this issue.
>
> Firstly, I wold like to thank all of you very much for the discussion and
> advice. These are great.
>
> Sorry for not replying to your mails on time, in the meantime I shot some
> photos to show the vignetting/falloff. The pics are in a folder at:
>
> http://www.photo.net/photodb/folder.tcl?folder_id=306074
>
> Would you please look at the photos and comment.
>
> At the end of the folder there are two photos from my Pentax Optio S
digital
> to show the reference. There is a tree branch on the right top corner on
the
> ones with cloudy sky, so don't bother about it. One of the photo, the "Sky
> with moon at f2, 1/1000, does show more falloff at the left side/edge. Is
it
> the shutter as someone mentioned in the discussion? But I didn't realize
any
> vignetting/falloff with my Summicron-M 2/90 ASPH.
>
> The vignetting seems to be stronger with blue object. Is it the nature?
>
> I feel the vignetting is far too strong. Or it is normal for the lens?
>
> Should I shoot some thing else to verify the vignetting?
>
> Thanks.
>
> Y. Li
>
>
> ----- Original Message -----
> From: "tripspud" <tripspud@transbay.net>
> To: <leica-users@mejac.palo-alto.ca.us>
> Sent: Sunday, May 18, 2003 3:01 PM
> Subject: Re: [Leica] Vignetting of Summicron M 2/28mm ASPH
>
>
> > Hi Henning,
> >
> > Look at any interior design magazine or architecture. The best
> > shots are large format. Now digital too. For large format black
> > and white prints you can pas on the center filter and adjust in
> > the darkroom. I had a 121 SA w/cf, but never really got a
> > chance to use it without a studio setup. Big flash is what
> > it takes to allow for the decreased f/stops with the center
> > filter. There's a great book out called The Photographer's
> > Assistant' which shows what a current studio is like.
> >
> > Cheers,
> >
> >
> >
> > Henning Wulff wrote:
> >
> > > At 7:59 PM -0400 5/17/03, Don Dory wrote:
> > > >Henning,
> > > >I was mostly thinking of one of the aspheric elements forward or
> backward in
> > > >space. Perhaps I am naive, but I think up to two stops vignetting in
> the
> > > >corners doesn't bother most people. What was described was a severe
> hot
> > > >spot in the center of the image. I don't think that even an
unpainted
> > > >portion of the lens barrel could cause a hot spot in the center; such
a
> hot
> > > >spot would move around the frame depending on where the source of
light
> was
> > > >coming from.
> > > >
> > > >One of my underlying assumptions in this whole discussion was that
the
> > > >original complaint was a real visible problem. Over the years, I
have
> > > >gradually realized that there is usually some basis of fact to
reported
> > > >problems. There is, of course, the occasional troll that throws
> gasoline on
> > > >a lighted match. That is usually pretty rare.
> > > >
> > > >Don
> > > >dorysrus@mindspring.com
> > >
> > > Don,
> > >
> > > The displacement of any element in _any_ direction will first be
> > > noticed in a loss of resolution and an increase in aberrations. If
> > > the displacement is axial, the effect will of course be symmetrical
> > > while radial displacement will produce non-symmetrical deterioration.
> > > Either type of displacement will produce very severe degradation well
> > > before the slightest effect of increased vignetting is seen.
> > >
> > > I don't think the post was a troll; rather a misunderstanding of the
> > > design aim point and the resultant performance parameters.
> > >
> > > I have noticed before that people coming from SLR's have different
> > > expectations of optical performance than those used to RF cameras,
> > > just as many cannot get used to the coincidence type rangefinders
> > > coming from AF SLR's. It can be difficult getting used to the
> > > different handling, just as the performance parameters of lenses of
> > > different construction can seem weird.
> > >
> > > My 21/2.8 ASPH, while having less vignetting (talking about optical
> > > vignetting due to lens design rather than physical vignetting due to
> > > mount or element diameter limitations) than the SA 21/3.4, still has
> > > more light falloff than any recent good Nikon, Canon or whatever
> > > 20/2.8. It is noticeable if you look for it, or if you are sensitive
> > > to it. Conversely, in all other respects it is a far superior lens
> > > then those same Nikon, Canon or whatever.
> > >
> > > The 21/2.8 ASPH is a very mild retrofocus design, constructed that
> > > way so that metering is possible with the M5,6,7 cameras. This helps
> > > the vignetting over that of the 21/3.4, but the strongly retrofocus
> > > 20/2.8 lenses for SLR's are better. There are a few tricks that are
> > > used to expand the exit pupil size at larger angles so that light
> > > falloff is less than demanded by cos^4, but at the present stage of
> > > development, to maintain the best overall performance within a given
> > > degree of retrofocus ratio will mean that there is more falloff with
> > > RF wideangle lenses than SLR lenses.
> > >
> > > The highest level of performance can still be achieved by using a
> > > nearly symmetrical construction, and letting light falloff be as it
> > > may. To compensate for this, a center filter is then used. This cures
> > > all the problems except price, size and lens speed. Performance will
> > > be stellar, as exhibited by modern LF designs.
> > >
> > > You can't have it all.
> > >
> > > --
> > > * Henning J. Wulff
> > > /|\ Wulff Photography & Design
> > > /###\ mailto:henningw@archiphoto.com
> > > |[ ]| http://www.archiphoto.com
> > > --
> > > To unsubscribe, see
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> >
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> > To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html
> >
>
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