balsam separation

<p>Occasionally when reading the description of used optical equipment I read 'signs of balsam separation'. Can anyone tell me what this looks like?</p>

<p>For example, like this:</p><div></div>

<p>thanks for the clear photo. Just a couple of quick questions:<br>

1. is the separation worsening in your lens?<br>

2. what camera is the lens from? I don't recognise the designation 'Pro - Tessar'</p>

<blockquote>

<p>1. is the separation worsening in your lens?</p>

</blockquote>

<p>No. However, I sold that lens a while ago, though (needed the money).</p>

<blockquote>

<p>2. what camera is the lens from? I don't recognise the designation 'Pro - Tessar'</p>

</blockquote>

<p>It's for the interchangeable front element of the Zeiss Ikon Contaflex Super cameras. The Pro-Tessars are pretty infamous when it comes to this issue.</p>

<p>Lens separation can also happen in the center of a lens, where I guess the image quality will suffer.</p>

<p>I think it does worsen very slowly. I have a lens that went from being like that Tessar in the picture to now only a nickel sized spot that is still clear in the center. However the lens is still sharp...</p>

<p>I imagine the 'rainbow colours' of the effect are due to a very slight relative movement of the cemented pair of the order of a few wavelengths of light - which may explain the minimal/no effect on image quality.</p>

<p>I was trained by Carl Zeiss on their cine lenses in the 1980's. I was told that Zeiss (West) used a method of "pressure cementing" elements together in the 1950's and '60's using some early optical cement, not balsam. I'm not sure if they did this to speed up production or to improve performance. Certainly their lenses in that era were some of the best glass available. Now, 50 years later, problems have emerged. As Bueh B's image at the top of the page shows, you get a rainbow-mirror effect in the seperation areas. I have had a few lenses like this and they all made fine pictures.</p>

<p>If somebody offered me a lens with "balsam seperation" I would consider it and run some film tests. I think the only problem would be a slight loss of light transmission. I'm sure you would get a substantial price discount. John Van Stelten at Focal Point may be able to get one of these lenses apart and re-cement it using a modern optical cement. So long as the lens didn't crack or deform when heated, the result should be excellent. Only problem is the Contaflex Pro-Tessars are worth very little. I have seen Contarex lenses with the same issues. I'm sure they would be worth repairing...</p>

<p>I have Rolleicord V, Xenar 3.5 lens. Several years back, almost twenty actually, the taking lens displayed a miniscule amount of delamination at the 5-7 o'clock region, extreme edge.</p>

<p> Today it has grown ever so slightly, perhaps the spread advancing about 10-15%. Zero affect on the images. Shouldn't be a significant worry.</p>