Archived posting to the Leica Users Group, 2003/05/18
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Y OK you win! Lens is totally unacceptable. Some people confuse light falloff with vignetting. 'Taint the same! Send that lens back. Jerry "Y. Li" wrote: > 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 http://mejac.palo-alto.ca.us/leica-users/unsub.html > > > > -- > > To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html > > > > -- > To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html