What causes bubbles in this lens?

[mark_stephan2]

<p>eBay item number: <strong>251679367407</strong><br>

This is a New FD 28 f2.0 lens and it has bubbles in what looks like the front element. I think it's common with this lens because I've seen them in other auctions. What causes these bubbles and does it hurt image quality?</p>

[Bill C1664885404]

<p>That's interesting...trying to study the photos, a couple things / questions come to mind:<br>

1) Is it really bubbles in the lens elements, or some sort of reflections ??<br>

2) Or if in the lens, is it really in the glass...in looking closely down inside, most "appear" to be on the walls / mechanical surfaces ??<br>

3) Lastly, I wonder why in the world the seller wouldn't at least comment on them ??</p>

[Lou_Meluso]

<p>Schneideritis<br>

<br>

black paint separation from inside lens<br>

Does not hurt image quality<br>

Google has more info</p>

[JDMvW]

<p>At one time before WWII anyhow, some people thought the presence of real bubbles in the glass was a sign of quality.</p>

[alan_swartz]

<p>Definitely bubbles under the black paint applied to the rough, ground edge of the second element. The rear of that element is so concave you can drink water from it, but its cup is so small in diameter that the edge of the glass is quite wide. That edge is nearly perpendicular to the lens axis, too, maybe only 15-20 degrees from perpendicular. When you look into the front of the lens, you're looking <em>through</em> that edge just as much as you are through the optical "cup" in the center of the element. Hence the black paint.</p>

<p>No idea why the bubbles form under the paint, but many (most?) 28/2.0 lenses have them. I had one that did. I have one that doesn't. Both had a far worse problem, a tiny element right next to the diaphragm that was nearly opaque with some sort of scum, and not just an oil film.</p>

<p>But the bubbles make no difference in image quality, since they are not in the optical path. Some speculate that they might reduce contrast by scattering light against the back of the first element. I was very happy with both of my copies of the lens, even after cleaning the other terrible element, and never saw any lack of contrast or saturation.</p>

[User_4754088]

<p>Just sold one of those last week, no bubbles in mine.</p>

<p><img src="http://www.timcarrollphotography.com/Assets/images/Sales/Canon28/28frontthru.jpg" alt="" /></p>

<p>$179 with no bubbles, front & rear caps, and Canon hood. That auctions seems a little high.</p>

<p>Best,<br>

-Tim</p>

[User_502260]

<p>The lens with the bubbles is a New FD. The example shown without the bubbles is an FD SSC. I also have an FD SSC and it has no bubbles. Could this be more common in New FD lenses?</p>

[User_4754088]

<p>I always believed that optically they were the same lens. Maybe the manufacturing practices were better on the older FD lenses compared to the newer FDn lenses.</p>

<p>Best,<br>

-Tim</p>

[User_502260]

<p>According to the Canon Camera Museum website the SSC lens has nine elements and the New FD lens has ten.</p>

[mark_pierlot]

<p>That's a gorgeous specimen of the 28/2 SSC, Tim. I would've bought it in a heartbeat had it been available to me.</p>

[User_4754088]

<p>Mark, it was in the classifieds for a week before it sold, and I mentioned it in a post on this forum (for which I got scolded). :-)</p>

<p>Sorry you missed it.</p>

<p>Best,<br>

-Tim</p>

[jim_bielecki1]

<blockquote>

<p>The lens with the bubbles is a New FD. The example shown without the bubbles is an FD SSC. I also have an FD SSC and it has no bubbles. Could this be more common in New FD lenses?</p>

</blockquote>

<p >Yes it is. This, apparently, is fairly common in the FDn version of the 28/2.0. And as others have pointed out, it's due to the loss of blackening along the edge of one of the elements. My FDn 28/2.0 is afflicted too. No real impact on image quality, best I can tell, but it will hurt re-sell value. At least it has for me. Who wants to buy a lens with bubbles along the edges?</p>

[jim_bielecki1]

<p>On a related note, I own the FD SSC version of the 28/2.0 and the FDn 28/2.0. Optically, the FDn version is a better lens, especially wide-open. Canon redesigned the optics, and it shows. The SSC version is somewhat soft wide-open, the FDn version is tack sharp. A noticeable difference.</p>

[phil_d]

I read somewhere that bubbles in glass were a sign of high quality....

 

Oh wait.. It was in leica lenses...

http://www.photo.net/leica-rangefinders-forum/00ZqbQ

[jim_bielecki1]

<p>It’s not bubbles in the glass. The blackening Canon used along the edges of the lens elements was poorly applied and is separating from the lens barrel. It looks like small dots all over the edge of the element. No impact on lens performance, best I can tell, but it looks like hell.</p>