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Lens with heavy coating marks - To buy or not to buy?


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<p>Hi folks,<br>

I have an opportunity to buy an old lens described as having "heavy coating marks on the front and rear elements" by a reputable dealer.<br>

This is a very nice Zeiss lens, and the price is good. However, would it be foolish to invest money in this lens? I assume it is fairly likely that the coating marks (esp. on the rear element) would affect image quality - am I correct in this assumption? And if I were to take the plunge, would it be possible to have the lens re-coated and polished to restore the image quality?<br>

Many thanks,<br />Raj</p>

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<p>Hi everyone,<br>

Thank you for your input - I had a feeling that it wouldn't be worth the hassle, and your collective opinion confirmed my suspicion. It's a Zeiss Contarex 85mm f2 lens, which is pretty uncommon, certainly at the price! The ones with fewer issues on eBay range from almost $900 to upwards of $2000!! The one with the coating marks is <$200, so you can understand my temptation :)<br>

Much obliged for your advice!<br>

Raj</p>

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<p>Mike - thanks, this is the reason for my difficulty. If it had been virtually any other lens, I would have considered it too much of a bother/risk, but the Contarex lenses are simply magnificent, not only in terms of results, but their build, look and feel. More sleepless nights ahead, methinks ... :)</p>
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  • 3 weeks later...

<p>http://www.4photos.de/camera-diy/Lens-Coating-Removal.html</p>

<p>http://www.mothers.com/02_products/05100-05101.html#&slider1=18</p>

<p>I don't see much of a description for the latter, but it looks like it should dissolve MgO but not scratch Mg.<br>

Maybe if also dissolves MgF2. Is that what the coating is?</p>

<p>Another article suggests that NaF solutions dissolve MgF2. HF will start dissolving the glass, though not so fast. I think if you keep at alkaline enough, NaF won't dissolve the glass, but might still dissolve MgF2.</p>

<p>Or maybe some acid will work on MgF2 but not on the glass. In those cases, you might want to take the lens elements out and treat them separately.</p>

-- glen

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<p>Thank you for the suggestions, Glen.<br>

I've decided not to proceed with the purchase, as I don't want to risk experimenting with my limited skills on a very beautiful and well-made lens. I'd rather pay more for a lens without these issues, and leave this one for someone with the skill and desire to revive it to its former glory.<br>

My thanks to everyone who offered comments and suggestions!</p>

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<p>Yes, I was posting in case anyone else wanted to know about coating removal, and because I still wasn't sure what would work and what wouldn't.</p>

<p>One could experiment with valueless lenses to know what might work on more valuable ones.<br>

I do believe that there is a chemical removal method, but am not so sure what it is.</p>

<p>I presume most here know, but from the articles I saw on coating removal, lenses can look pretty bad and still take fine pictures. The contrast is reduces a little bit, but then it also is reduced with coating removal. </p>

<p>Then again, the seller could reduce the price if no-one else is interested in it for the same reason.</p>

-- glen

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<p>The problem with the lens in this case was that the seller reported heavy coating marks on the front and rear elements; though the former didn't worry me, the latter were much more concerning for their potential impact on image quality. And not being able to examine it prior to purchase (it was an online listing) made the whole thing seem a little too risky for a $200 price tag.<br>

Definitely worth considering experiments along the lines you suggest with cheap lenses.</p>

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