Archived posting to the Leica Users Group, 2007/11/10

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Subject: [Leica] Img: Radioactive lens fix works
From: henningw at (Henning Wulff)
Date: Sat Nov 10 15:55:15 2007
References: <> <p06230908c35b9acccc72@> <> <>

>This sounds like a very plausible theory, Anders.
>As I stated before, I don't doubt Len's observation. But -and as an 
>answer to Henning- the 2 visual proofs of this observation were not 
>were not really made in identical circumstances.
>That's why I suggested to documented them in a similar conditions.
>Even from his low res jpegs, I did the test, balanced them (black 
>point, white point, mid gray) and put them in Lab colour -the widest 
>color space as you may know- to make them comparable*.
>There still is a visible difference. But at least the comparison has 
>been made on a par level.
>So let's not start doing critical image comparisons in different 
>conditions, on different screens and with low res sRGBs if we want 
>to use these a studying material.
>Even if visual comparison does not give the right explanation for 
>the reason of succes for this treatment.

I have seen thorium glass elements that have aged. I've also seen 
many lenses with fungus. Fungus is a surface condition. This is an 
internal condition.

Changing the colour model from RGB to LAB doesn't help per se; it 
might help you quantify the differences better if you are more 
familiar with that model but it doesn't have anything to do with the 
colour space

As far as colour space is concerned: yes, there are a lot colour 
spaces with wider gamuts, such as Adobe RGB or even better Prophoto 
RGB, but that is little help when the original is a small sRGB image. 
But even here, the differences are readily measurable and discernible 
and critical comparison is not necessary to see that there is a 
definite difference. If looking at the low-res sRGB jpgs goes against 
the grain, read Len's description. He feels that the jpgs are 
representative of what he sees, so let's accept it.

As I said, the mechanism is not clear to me nor have I been able to 
find out what it might be, but it obviously responds to low energy UV.

    *            Henning J. Wulff
   /|\      Wulff Photography & Design
  |[ ]|

Replies: Reply from philippe.orlent at (Philippe Orlent) ([Leica] Img: Radioactive lens fix works)
In reply to: Message from len-1 at (Leonard Taupier) ([Leica] Img: Radioactive lens fix works)
Message from anders.nygren at (Anders Nygren) ([Leica] Img: Radioactive lens fix works)
Message from philippe.orlent at (Philippe Orlent) ([Leica] Img: Radioactive lens fix works)