Archived posting to the Leica Users Group, 2007/10/13

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Subject: [Leica] George: 28mm Summicron IR problem
From: grduprey at mchsi.com (grduprey@mchsi.com)
Date: Sat Oct 13 18:06:59 2007

Mine seems to be free of this problem.  Nice even alumination over the 
entrie field.  It has higher contrast when compared to the Summicron though, 
or so I have been told.

Gene

-------------- Original message from Leonard Taupier <len-1@comcast.net>: 
-------------- 


> Steve, 
> 
> So far that's two for two. (George's and my son's). I had to borrow 
> my sons as I only have the Elmarit. It would be interesting to know 
> how the new Elmarit asph fares. 
> 
> Len 
> 
> 
> On Oct 12, 2007, at 5:11 PM, Steve Barbour wrote: 
> 
> > 
> > On Oct 12, 2007, at 2:10 PM, Leonard Taupier wrote: 
> > 
> >> George, et al. 
> >> 
> >> I've verified a problem with the 
> > 
> > (or my) ?? 
> > 
> > 
> > ....tested one sample, or multiple cron 28's....? 
> > 
> > 
> > 
> >> 28mm Summicron on an M8 and IR filter when trying to take Infra 
> >> Red photos. 
> >> 
> >> There is a hot spot present in the center of the frame when trying 
> >> to take IR photos with the above setup. The problem looks like 
> >> flare, a circle of low contrast in the center of the frame. The 
> >> problem is most noticeable at the smaller lens openings where the 
> >> hot spot is clearly defined. As the lens is opened up the hot spot 
> >> becomes larger and less pronounced but the center area is still 
> >> lower contrast. I did not see this at f2 and f2.8. Here is a photo 
> >> taken at f16. 
> >> 
> >> > >> 28mmSummicronIR.jpg.html> 
> >> or 
> >> http://tinyurl.com/yreo78 
> >> 
> >> I used two M8 cameras for the test. All photos were taken on a 
> >> tripod with the sun directly behind the camera and shaded by my 
> >> body. The filter was a Hoya R72. A lens hood was on the lens. The 
> >> problem showed up with both M8 cameras. 
> >> 
> >> The same test was also performed using the 28mm f2.8 Elmarit (non- 
> >> asph), 35mm Summicron asph, 24mm Elmarit asph and the 21mm Elmarit 
> >> asph. Only the 28mm Summicron asph showed the hot spot problem. 
> >> 
> >> The problem does not show up when using a Red R60 filter. 
> >> 
> >> Len 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> _______________________________________________ 
> >> Leica Users Group. 
> >> See http://leica-users.org/mailman/listinfo/lug for more information 
> > 
> > 
> > _______________________________________________ 
> > Leica Users Group. 
> > See http://leica-users.org/mailman/listinfo/lug for more information 
> 
> 
> _______________________________________________ 
> Leica Users Group. 
> See http://leica-users.org/mailman/listinfo/lug for more information 

Replies: Reply from imagist3 at mac.com (Lottermoser George) ([Leica] George: 28mm Summicron IR problem)