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11-22-2010, 10:48 PM   #1
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Strange ring of oil

Inside of one of my lenses. It's at the VERY edge of the lens element (internal, not front or back). Does not seem to move, or affect quality of picture at all.

I've read this could be lens separation - seems unlikely in a modern lens right? Also read that it could be oil on the blades - will this get worse with time or will the lens stay as it is?

Thanks.

11-23-2010, 10:09 AM   #2
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Please help, I'm very worried.
11-23-2010, 10:20 AM - 1 Like   #3
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Can you post a picture of the strange ring? It'd be much easier to try to help if we saw what we are talking about.
11-23-2010, 10:25 AM   #4
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a shot of the "ring" would be of great benefit.

in a lens, the only location where there may be oil, but it should be contained within grease and not freely moving around the lens, is the focusing and zoom helixes.

this is generally the source of oil when it appears in the lens.

One thing to note is that oil will separate from grease due to vibration, mechanical working (pressure) and temperature.

Has the lens been exposed to extremes of temperature, or vibration?

11-23-2010, 10:26 AM   #5
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Is there any way you can show us?

Yes, lens groups can separate but I've never seen it even in the oldest SLR lenses I've owned. Most likely if a group is separating, the lens was dropped at some point. It IS repairable by a qualified person if it becomes a problem but unless you intend to use this lens on a Film camera, I wouldn't worry too much about it until it worsens (if it does).. It could also be haze from over zealous cleaning (drenching the lens with cleaning fluid and leaked inside the lens).

Re the Oil. Far more common. You can determine of you have it on the blades by exercising the aperture. Stop the lens down to f16 (or whatever the highest number is), and actuate the lever on the rear of the lens. The blades should snap back without Any delay. If they Do drag, you will find your photos with the lens are likely over exposed. Again, it's curable but is difficult because the entire lens must come apart for a thorough cleaning. Other problems I've seen with dragging apertures however had nothing to do with oil but weak springs inside the lens. My Mamiya 55 f1.4 had a dragging aperture and the blades were like new. I finally just disabled the A setting on the lens (m42 lens), and now it's just a full manual lens.

11-23-2010, 10:45 AM   #6
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Thanks. I had a hell of a time trying to photograph it... it does not seem to show up as clearly as i does with natural light and eyes (i.e., flash makes it disappear or something!) So keep in mind the appearance of a "tiny" ring of oil is more apparent in person than in these pictures. I also had to hold the aperture wide open with one hand while i took the picture with the other. Anyways this is the best I could do.

I realize this is finicky but... that's how I am. Like I said it does not seem to affect the photographs so if it won't progress I'll stop thinking about it.





11-23-2010, 01:21 PM   #7
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Is it nothing to worry about?
11-23-2010, 01:50 PM   #8
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If we are looking at the white-ish area around the edge of the inner glass, could be separation, could be something else but that is sort of what separation looks like.. I doesn't look like oil. For now I would just keep an eye on it (unless the lens happens to be under warranty). What kind of lens Is it?



11-23-2010, 01:58 PM   #9
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it is really hard to tell, but it almost looks like the edge of the element,

has the optical performance changed.

I am not sure about this obviously, but it might indicate decentering if it is truely the edge of the glass. It could also be an area where something (motion) has caused the coatings to be damaged at the edge.

decentering would be indicated by differing sharpness side to side, and also if this is seen all the way around the lens or on one side.

check the corner detail and look for differences, that is where it would be most obvious.


It may cause nothing and it may have been there all along, just never noticed, or it may be the result of a hard shock.

Any big lumps and bumps in the len's history?
11-23-2010, 02:05 PM   #10
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I purchased a DA 70 used, in apparently perfect condition... so I have no idea about the lens' history. Unfortunately I cannot return it, so I need to think about this as a "damage control" situation if anything. I will inspect for sharpness problems, but for the most part this lens performs 100% to my expectations. It took me a few weeks to realize there was anything going on.

My only worry is that this might be something progressive. If it will stay the way it is, I am fine with it.
11-23-2010, 02:06 PM   #11
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QuoteOriginally posted by Lowell Goudge Quote

I am not sure about this obviously, but it might indicate decentering if it is truely the edge of the glass. It could also be an area where something (motion) has caused the coatings to be damaged at the edge.
Would it be possible if this ring goes all the way around the lens? I would think decentering would have this "ring" only show on one side...
11-23-2010, 02:11 PM   #12
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QuoteOriginally posted by paperbag846 Quote
I purchased a DA 70 used, in apparently perfect condition... so I have no idea about the lens' history. Unfortunately I cannot return it, so I need to think about this as a "damage control" situation if anything. I will inspect for sharpness problems, but for the most part this lens performs 100% to my expectations. It took me a few weeks to realize there was anything going on.

My only worry is that this might be something progressive. If it will stay the way it is, I am fine with it.
QuoteOriginally posted by paperbag846 Quote
Would it be possible if this ring goes all the way around the lens? I would think decentering would have this "ring" only show on one side...
This is all why I say keep an eye on it. If it's separating (or decentered) it will either have to be taken the rest of the way apart to repair it, or replaced.

11-23-2010, 02:19 PM   #13
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Any idea how much a repair like that could cost me?

The picture shows exceptional sharpness... maybe a tiny bit of corner softness, but nothing that really matters. To be honest I'm having trouble telling because I don't know if it has anything to do with this sample, or just the lens itself (all of my lenses are of course softer at the corners!) If it will stay this way forever, I'm not so concerned... or is this likely to be a "progressive" issue?
11-23-2010, 02:58 PM   #14
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QuoteOriginally posted by Lowell Goudge Quote
check the corner detail and look for differences, that is where it would be most obvious.
I appears that one corner is slightly softer than the other ones. But I REALLY need to get in there to notice it. I suppose this could be considered VERY mild decentering then.

What are the chances that it will just stay as is? Would it require another bump to make it worse... or is something inside breaking down and will it all slowly shift with time?

Thanks so much guys... I'm much less worried now, because if it is decentered, and stays the way it is right now, the degree of corner blurriness is so low that I would never had noticed, if I didn't notice the ring inside of the lens.

If it will stay like this, or there is a good chance of it, I will not think about it any longer .
11-23-2010, 03:45 PM   #15
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I'm thinking that the repair cost would be prohibitive but don't know that for a fact. You could try writing Pentax in your area and asking the repair facility. The only way to really tell what's going on is with a collimator (a device used for aligning optics) as far as decentering.

Fact is though, you have a better picture in person of what it exactly looks like than we are seeing in the photos so (on my part anyway) this is basically guess work. If you're happy with what the lens gives you, use it in good health and don't stress about it (if there are in fact no return options available).

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