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

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Subject: [Leica] George: 28mm Summicron IR problem
From: imagist3 at mac.com (Lottermoser George)
Date: Fri Oct 12 15:44:48 2007
References: <7FA6647D-A36C-4A86-84B3-A4756DA8FB77@comcast.net> <673C7DEC-A9C1-490A-8F6F-821246CF27FC@comcast.net>

It is hard to imagine that the IR "hot spot" phenomenon can be  
equated to vignetting.
The "hot spot" does appear "over exposed." However, it also displays  
a lack of contrast; which makes nearly impossible to correct with any  
"vignetting filters."

I've been led to believe that the IR hot spot phenomenon also appears  
in the use of IR films.

Has anyone seen this phenomenon on IR films with particular wide  
angle lenses?

Regards,
George Lottermoser
george@imagist.com



On Oct 12, 2007, at 5:34 PM, Tom Schofield wrote:

> "Problem" or "characteristic"?  Perhaps another way of looking at  
> it is that the 28mm Summicron vignettes in the IR spectrum, and you  
> are exposing for the outer field rather than the center, leaving  
> the center overexposed.  That raises an interestig question -- does  
> vignetting vary according to the color or spectrum of the light?   
> Too bad Erwin is not here for such Q's!


In reply to: Message from len-1 at comcast.net (Leonard Taupier) ([Leica] George: 28mm Summicron IR problem)
Message from tomschofield at comcast.net (Tom Schofield) ([Leica] George: 28mm Summicron IR problem)