Archived posting to the Leica Users Group, 2007/10/12

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Subject: [Leica] George: 28mm Summicron IR problem
From: kididdoc at cox.net (Steve Barbour)
Date: Fri Oct 12 14:15:04 2007
References: <7FA6647D-A36C-4A86-84B3-A4756DA8FB77@comcast.net>

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.
>
> <http://gallery.leica-users.org/v/LeonardT/Infra_Red/ 
> 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
>
>
>
>
>
>
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Replies: Reply from len-1 at comcast.net (Leonard Taupier) ([Leica] George: 28mm Summicron IR problem)
Reply from imagist3 at mac.com (Lottermoser George) ([Leica] George: 28mm Summicron IR problem)
In reply to: Message from len-1 at comcast.net (Leonard Taupier) ([Leica] George: 28mm Summicron IR problem)