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

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Subject: [Leica] George: 28mm Summicron IR problem
From: len-1 at comcast.net (Leonard Taupier)
Date: Sat Oct 13 18:55:01 2007
References: <101420070059.28034.47116A070007353B00006D82219791299503010CD2079C080C03BF970A9D9F9A0B9D09@mchsi.com>

Hi Gene,

I've only got the Hoya filter. I really need to get a 60mm so I may  
order a B+W and a step up ring 46 to 60. I'm not sure but I think  
George may be using a Hoya on his Summicron as well. My son is taking  
his 28mm Summicron back to Boston so I can't do any further testing  
until Thanksgiving when he returns. I'm glad to hear the new 28  
Elmarit asph is fine though. I love that focal length for IR and the M8.

Len


On Oct 13, 2007, at 8:59 PM, grduprey@mchsi.com wrote:

> Len,
>
> Have you tried a different brand of IR filter?  Don't have the  
> summicron, but my 28 Elmarit Asph does not show this.  I have the  
> Heliopan ir filter on it.  Don't know if changing the filter will  
> make any difference, but worth a try.
>
> gene
>
> -------------- Original message from Leonard Taupier  
> <len-1@comcast.net>: --------------
>
>
>> George, et al.
>>
>> I've verified a problem with the 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
>
> _______________________________________________
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> See http://leica-users.org/mailman/listinfo/lug for more information


Replies: Reply from Jim at hemenway.com (Jim Hemenway) ([Leica] IR filters)
Reply from imagist3 at mac.com (Lottermoser George) ([Leica] George: 28mm Summicron IR problem)
In reply to: Message from grduprey at mchsi.com (grduprey@mchsi.com) ([Leica] George: 28mm Summicron IR problem)