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01-28-2013, 04:09 AM   #1
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Help - Blurness problem encountered, on lens element?

Hi, fellow Pentaxforum members.

I've encountered a rather alarming situation with my DA35 Macro Ltd lens.

I removed the lens cap and the back cap, and manually pushed the aperture blades control lever, to open up the aperture fully.

Then I looked through the lens, via the rear element.

I saw a strange "cloudiness" or "fuzziness", occupying a substantial portion of the circle, marring the otherwise clear image.

To me at least, it does not look like fungus, in the sense that I do not see fine fibre-like strands as normally seen with fungus. It's just a blurness, and not uniform in its texture - ie. it appears to be spread out roughly in a petal-like "pattern", similar to the petals of a rose, with it being centred just slightly off the centre of the circle. (Mind you, it isn't some ghost reflection of the aperture blades, since the lens was wide open).

Not very sure, but I suspect that one of the lens elements has somehow been affected - maybe an inner element, or my suspicion is the rear element iteself.

Strange thing is, when I look at the rear element at a glancing angle (with illumination), as opposed to looking through the rear element as described above (ie. I'm examing the outer surface of the rear element), I see nothing at all - very clean.

Anyone experienced something similar, and how did you solve it?

I would not rule out fungus of course, perhaps of a different variety (ie. has no fine fibre-like filaments).

Appreciate your feedback and advice, and thank you very much.

01-28-2013, 04:20 AM   #2
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Condensation ?
01-28-2013, 04:32 AM   #3
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Have you noticed any problems with the pictures it takes,
at both wide (f/2.8) and narrow (like f/11 or f/16) apertures?
02-06-2013, 09:43 PM   #4
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Lens "fog"

Hi,

Sorry for such a late response from me. I brought the lens to my local technician who says it is not fungus but rather "fog". Not too sure what he exactly meant by that but perhaps it's CONDENSATION as suggested by kh1234567890. He also said it was beyond his ability to rectify, short of sending the lens back to Pentax Japan.

What would you normally do in such a situation?

If it is condensation, meaning it is nothing more than very fine water droplets deposited on one of the internal lens elements, do you think leaving it for a week or two in a anti-humidity cabinet will solve the problem?

Thanks again for the help.

02-06-2013, 11:31 PM   #5
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Lenses aren't airtight, so the condensation should have cleared up by now. My suspicion would be fungus or delamination.

Last edited by Ikarus; 02-07-2013 at 12:17 AM.
02-07-2013, 05:45 AM   #6
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If it is not water condensation, which as you say a day or two in a dry cabinet should remove, then it could be some other stuff such as lubricant. Did you ever leave the lens somewhere really hot ?

Delamination does not usually start from the centre of a lens element and fungus is unlikely to have grown that fast and normally has a fairly typical filament-like appearance.

I would bag the lens uncapped with some fresh desiccant bags, leave it somewhere warm for a while, periodically spinning the focus ring, if I remembered, and see if the haze disappears or changes in extent.
02-07-2013, 06:49 AM   #7
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If it was simple condensation, I think the technician would have been able to fix it. Does the lens include glued laminated elements? The lens cement may have failed and the fog is sandwiched between layers of glass.
02-07-2013, 10:28 AM   #8
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QuoteOriginally posted by DeadJohn Quote
Does the lens include glued laminated elements?
Yes, it does. See block diagram here.

02-07-2013, 12:28 PM   #9
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QuoteOriginally posted by Ikarus Quote
Yes, it does. See block diagram here.
It should be easy to tell if it is the cemented doublet splitting up - this is in front of the diaphragm.
02-07-2013, 02:01 PM   #10
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Hi again, everyone.

First of all let me say a big "thank you" to all of you – I really appreciate all the concern shown, with good theories and discussion.

One thing to clarify - up until the point when the technician phoned me to say it was "fog", the lens wasn't placed in a dehumidifier cabin. (At least, I don't think so, since I did not give him any such instruction.) Please bear in mind that this is Malaysia, where it's humid, so if my lens were just left on a shelf or workbench by the technician, it's hard to say whether it would have been able to "dry up", since the surrounding atmosphere can be pretty damp anyhow.

It was only after he rang me that I suggested the lens be placed in a cabinet and checked after a week or two to see if things cleared up on their own. Failing which, I may have no choice but to send it to Japan. If indeed it is a glue issue (element 3/4), then that would seem to be the right course of action, anyhow.

But guys, what do you all think Pentax Japan will do? Will they entirely replace elements 3/4? Or pry them apart, clean them up, and re-apply fresh glue – if such a process is even possible?

One thing strange though – so far as I can tell, the glue failure (if that’s what it is) did not seem to have afftected the image quality. Certainly I did not see significant loss of contrast, whether at big or small apertures.

kh1234567890, no I did not leave the lens any place hot. It was normally kept in a plastic container (practically airtight, but with no dessicant inside), with the container kept in a room which has the air-conditioner switched on about 8-10 hours a day.

Also, you mentioned "It should be easy to tell if it is the cemented doublet splitting up - this is in front of the diaphragm." What did you mean by that?

Once again, thanks a lot to all of you.
02-07-2013, 02:49 PM   #11
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QuoteOriginally posted by KDAFA Quote
I suggested the lens be placed in a cabinet and checked after a week or two to see if things cleared up on their own.


This sounds like a good first step.

If condensation has made its way into the air gaps
between elements 5/6 or 8/9,
it could take a while to clear.

QuoteOriginally posted by KDAFA Quote
Failing which, I may have no choice but to send it to Japan. If indeed it is a glue issue (element 3/4), then that would seem to be the right course of action, anyhow.
QuoteOriginally posted by KDAFA Quote
But guys, what do you all think Pentax Japan will do? Will they entirely replace elements 3/4? Or pry them apart, clean them up, and re-apply fresh glue – if such a process is even possible?
I would recommend you to read

The Zeiss Ikon Contax Camera Repair Website - Overhauling A Contax IIA/IIIA - Lenses

Although it applies specifically to Zeiss lenses, it may be relevant anyway.
It suggests that an overall fog would not be typical of glue issues,
but rather that they would make themselves known
with bubbles (in balsam) or "iridescent edge separation" (with epoxy).
There are illustrations of what those look like.
Later, there is a discussion of possible repair methods.
02-07-2013, 04:25 PM   #12
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QuoteOriginally posted by KDAFA Quote
Hi again, everyone.
Also, you mentioned "It should be easy to tell if it is the cemented doublet splitting up - this is in front of the diaphragm." What did you mean by that?
Looking at the cross-section diagrams, the cemented pair is elements 3 and 4 counting from the front of the lens and is in front of the aperture iris. So by looking from the back of the lens you should be able to tell which side of the diaphragm the cloudy element is on. I would still suspect that moisture somehow got into the nearly sealed space between the two rear elements and condensed there. A spell in a dry cabinet should eventually cure it.

In Malaysia I would invest in a good dry cabinet and use it. During his couple of years in Singapore my son did - even though he's a Canon person and his lenses are the size of small tree trunk logs ...
02-19-2013, 08:32 AM   #13
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Hi again,

Well, after 2 weeks in the technician's cabinet the fog is still there, so off to Pentax Japan the lens goes.

kh1234567890, yes I have purchased a de-humidifier cabinet.

Thanks a lot guys, for all the help and tips given. Really appreciate it.
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