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04-24-2012, 02:25 PM   #1
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Dust or air bubbles inside lens (with picture)

While inspecting two old SMC M lenses from my father (28mm/2.8 & 50mm/1.7) I noticed countless extreme small dust particles, or tiny air-bubbles on one element of both lenses. It is only noticeable when I use a bright LED light on it. As I don't have my K5 yet I can't test it out, but to me both lenses are looking pretty good without using the LED.

Any thoughts what it could be and if they're still usable?

PS. brown and other colored spot are just reflections of course.

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04-24-2012, 02:46 PM   #2
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I have a lens w/ a similar issue. From what I could find out, it may be vaporized oil from the aperture blades. Oddly, I don't seem to see where it makes much difference in the quality of my pics.
04-24-2012, 03:12 PM   #3
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Probably still usable, I'd suggest giving it a clean if you can. A lens hood may also minimize the problem.
04-24-2012, 03:48 PM   #4
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Separation of cemented elements?


Steve

(...always the pessimist...)

04-24-2012, 04:54 PM   #5
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QuoteOriginally posted by stevebrot Quote
Separation of cemented elements?
That's what I think too. Dust doesn't look like bubbles, but element separation can look that way.
04-24-2012, 08:40 PM   #6
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I had a Vivitar-Kiron 24/2 that looked like that. Element separation; no reasonable cure, except cannibalizing another lens. I say "no REASONABLE cure" because the tech I dealt with said it *could* be done but would probably cost about US$500. Yeah, an expert could dismantle and re-glue the elements. Or I could buy three replacements for that cost. Hmmm...
04-24-2012, 08:44 PM   #7
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As an add-on, my lens with element separation had very smooth bokeh. I always wondered whether it was a side-effect of the separation.
04-24-2012, 11:01 PM   #8
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I don't know what all is involved with element separation, but it doesn't sound good. As long as I can take acceptable pics with the lens, I suppose it's okay, but what does this mean with respect to the life of the lens? Is going to get slowly worse or just fall apart suddenly some day. Mine is a macro lens, and I have no replacement for it, but I have to be able to count on it.

(I did see pics of a lens that sure looked like the op's pic and like my lens, and the diagnosis was oil vaporization. Is there a way to tell the difference between that and element separation?)

Thanks.

04-24-2012, 11:13 PM   #9
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QuoteOriginally posted by mgvh Quote
I don't know what all is involved with element separation, but it doesn't sound good. As long as I can take acceptable pics with the lens, I suppose it's okay, but what does this mean with respect to the life of the lens? Is going to get slowly worse or just fall apart suddenly some day. Mine is a macro lens, and I have no replacement for it, but I have to be able to count on it.
IIRC element separation (ES) results when lenses of a certain vintage, whose elements are adhered with certain cements, dry out. IIRC a pine(?) resin is used as glue, and the edges of the joined elements are sealed. But after some time the seals break down, air leaks in, and the glues dries, decomposes, no longer holds the elements together.

ES is not self-healing. It will only get worse. Over a period of about 6 months, I could see more and more bubbles (more separation) in the Kiron 24/2. IIRC it is hastened by physical shocks and dry climates. No, the lens won't suddenly die (unless you drop it), it'll just get sicker and sicker. For general photography, you could get away with calling it a "romantically soft" lens. For macro work where sharpness is vital, you're screwed.

I could be wrong about ES on your lens. It could be dust, although I've never seen such dust in a lens. One indication: If you leave the lens alone for a few months and more bubbles appear, it's probably ES.
04-24-2012, 11:15 PM   #10
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Thanks for all the replies! Never heard of it though. But good to know anyway! I will give it a try when I have my K5 and see if its still usable. Guess that's the only way.

A quick search on the internet describes it as: 'Like a patch of oil when the sunlight hits it. There will be an iridescent rainbow colored area, usually along the edges. The shape varies, but it's typically crescent or wave-like.' That's not exactly the case here though, or are there just different kinds of lens seperation?

QuoteOriginally posted by mgvh Quote
(I did see pics of a lens that sure looked like the op's pic and like my lens, and the diagnosis was oil vaporization. Is there a way to tell the difference between that and element separation?)
I'm wondering what the difference is as well! Do you have those similar pics with Oil vaporization? Thanks!

Last edited by Tomm; 04-24-2012 at 11:24 PM.
04-25-2012, 02:54 AM   #11
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It just looks like dust to me. To the people seeing separation: Note that he's using a LED light. Not any other kind of light. This stuff is almost invisible in normal light, and I own no lenses older than a year where it doesn't show up (to some degree, usually less than in this picture) with a LED light.
04-25-2012, 07:47 AM   #12
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QuoteOriginally posted by RioRico Quote
IIRC a pine(?) resin is used as glue
Yep, resin (Canadian Balsam cement), though the source is the Balsam Fir, not pine.

As for dust vs. separation...close examination with a magnifying glass or loupe (I use a junk 50mm lens) with oblique illumination from the rear will help to tell the difference. If it dust, it has to be the filthiest lens I have ever seen. Refuge' from one of Iceland's recent eruptions perhaps?


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04-25-2012, 10:36 AM   #13
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@drougge: Yes, I do really only see the haze when I use a LED light. A google search for images of lens w/ haze shows similar looking stuff. From what others note and from my tests, I'm not noticing a problem w/ sharpness, but there may be a slight loss of contrast.
04-30-2012, 08:01 PM   #14
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Pentax M 50-1.7 and M 28-2.8 do not have cemented elements.(the 50 has a cemented rear pair). Most likely bad dust, fog or start of fungus. See lens diagrams at Bojidar Dimitrov's Pentax K-Mount Page
04-30-2012, 08:47 PM   #15
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QuoteOriginally posted by RioRico Quote
I had a Vivitar-Kiron 24/2 that looked like that. Element separation; no reasonable cure, except cannibalizing another lens. I say "no REASONABLE cure" because the tech I dealt with said it *could* be done but would probably cost about US$500. Yeah, an expert could dismantle and re-glue the elements. Or I could buy three replacements for that cost. Hmmm...
I have a 20mm Takumar with beginning separation. I got two estimates on it to fix it from people that actually do that sort of thing, and both were $150ish to a max of $200. $500 sounds a bit high. It *is* doable yourself if you really want -- involves dismantling and boiling the elements to get the glue off and then putting new stuff on. I am unclear what happens to MC coatings when boiling the elements. Probably lose those...
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