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Archive 2011Problems with old lens elements
p.1 #1Problems with old lens elements
Any experience with degradation of lens element coating (such as SSC by Canon) and lens element doublet separation ?
* How did the problem manifest itself in IQ ?
* What did you see when inspecting the culprit element(s) ?
* How was the problem remedied ?
* How did the problem manifest itself in IQ ?
* What did you see when inspecting the culprit element(s) ?
* How was the problem remedied ?
Apr 16, 2011 at 06:40 AM
p.1 #2Problems with old lens elements
Haven't seen coating degradation although some old 50s or 60s coatings are very soft and easily damaged like that on Angenieux lenses or the internal coatings on Meyer Optik Goerlitz lenses. Some places like Arax in the Ukraine (at least they used to anyway) offer recoating but it's expensive and you have to decide if the lens is worth it.
I have seen element separation or the start of it though. You can get separation on lenses with elements that used Canada balsam as an adhesive and in a lot of cases, the beginnings can be observed at the edges where you might see a sort of yellowy hazy ring around the circumference when looking through the lens. Depending on how bad it is though, you might not actually see it in the final image in practice, especially if you stop the lens down.
OTOH, the biggest problem with full separation is ensuring that the elements are properly optically centred when the doublet etc. is reassembled, because if they aren't, this will definitely impact IQ with uneven sharpness for example across the frame which you will likely see. Balsam melts when heated and it might be possible to sort things out by observing and marking the positions of the individual elements and then heating the part and sliding the elements around to spread the adhesive again. Return the elements to the original positions, make sure everything is back to where it was before and allow the balsam to harden. I've never tried this so take it with a pinch of salt that it works...
I have an Exakta mount Zeiss Jena Flektogon 2.8/35 that had an internal mark on a cemented doublet and as the lens wasn't too expensive, I separated the doublet using gentle heat from a hairdryer so not to crack anything, removed the adhesive and mark then applied a tiny spot of watch oil to bond the elements back together. It looks OK and I can see no discernable colour cast from the oil but whether it's properly centred is another matter as I haven't got round to using it yet...
Edited on Apr 16, 2011 at 07:28 AM · View previous versions
I have seen element separation or the start of it though. You can get separation on lenses with elements that used Canada balsam as an adhesive and in a lot of cases, the beginnings can be observed at the edges where you might see a sort of yellowy hazy ring around the circumference when looking through the lens. Depending on how bad it is though, you might not actually see it in the final image in practice, especially if you stop the lens down.
OTOH, the biggest problem with full separation is ensuring that the elements are properly optically centred when the doublet etc. is reassembled, because if they aren't, this will definitely impact IQ with uneven sharpness for example across the frame which you will likely see. Balsam melts when heated and it might be possible to sort things out by observing and marking the positions of the individual elements and then heating the part and sliding the elements around to spread the adhesive again. Return the elements to the original positions, make sure everything is back to where it was before and allow the balsam to harden. I've never tried this so take it with a pinch of salt that it works...
I have an Exakta mount Zeiss Jena Flektogon 2.8/35 that had an internal mark on a cemented doublet and as the lens wasn't too expensive, I separated the doublet using gentle heat from a hairdryer so not to crack anything, removed the adhesive and mark then applied a tiny spot of watch oil to bond the elements back together. It looks OK and I can see no discernable colour cast from the oil but whether it's properly centred is another matter as I haven't got round to using it yet...
Edited on Apr 16, 2011 at 07:28 AM · View previous versions
Apr 16, 2011 at 07:13 AM
p.1 #3Problems with old lens elements
Separation of two bonded lens elements could be seen sometimes as rainbow colors in the glass.
I have heated the last days a Agfa Magnolar lens element with separation, and tried to get rid of the separation with moving and pressing the hot elements together while the Canada Balsam was still hot. In my impression it was afterwards a bit better, but not completly away.
At the moment I want to buy some Canada Balsam, and want to try to recemment the lenses. If that works, I could try the same with a Rodenstock Rodagon 80 - with a test setup before/after.
I have heated the last days a Agfa Magnolar lens element with separation, and tried to get rid of the separation with moving and pressing the hot elements together while the Canada Balsam was still hot. In my impression it was afterwards a bit better, but not completly away.
At the moment I want to buy some Canada Balsam, and want to try to recemment the lenses. If that works, I could try the same with a Rodenstock Rodagon 80 - with a test setup before/after.
Apr 18, 2011 at 04:03 AM
p.1 #4Problems with old lens elements
I had a Hassey wide angle lens that had an edge seperation. I could never see it in the photos or getting any larger, so i did nothing to it.
Cheers
Harry
Cheers
Harry
Apr 18, 2011 at 05:43 AM
p.1 #5Problems with old lens elements
Hi Peter,
I've had a few lenses with separation. It's usually most noticeable around the outer periphery of the element or elements in question as slightly cloudy areas. I guess this is what's called 'edge separation'. Early-stage edge separation appears as one or a few semi-circular areas that are less transparent than the glass, or sometimes very shiny looking. Over time, they can grow larger and join with other spots, until there's a noticeable effect all around the edge of the element.
Sometimes, it's difficult to distinguish separation from some types of fungus. Separation doesn't have any striations or spidery arms like many types of fungus, but not all fungi look like this. For example, I have a lens in the shop right now to determine if its rear element has a case of fungus or very widespread separation. If it's fungus on an external surface (as opposed to between elements), then there's a 50% chance that Dave at CRC can clean it up just fine. Most cases of separation that I've had really didn't affect IQ, but it bugs the heck out of me. I've returned one lens for separation (Planar 50/1.7), which is few in comparison with the numbers I've returned for fungus (3) or scratches on the glass (2). Of course, this doesn't include the ones that I've either damaged myself, or which have sprouted or separated when in my posession.
As far as what to do goes, I guess it depends on the value of the lens. In most cases, I think it's less expensive and far less aggravating to try to find another copy of the lens, even if it's relatively expensive. Of course, the ideal solution is to locate one in "as is" condition that has different 'challenges' than your particular case. I actually did this successfully for an old Vivitar Series 1 35-85mm/2.8 zoom that I carelessly scratched on the front element. I found a 'beater' for a really low price, had Dave swap front elements, sold the fixed one for a decent price, and used the crapped-out one for an experiment on the effects of paint ball impacts on protective filters. Win-win situation.
Cheers, Jim
I've had a few lenses with separation. It's usually most noticeable around the outer periphery of the element or elements in question as slightly cloudy areas. I guess this is what's called 'edge separation'. Early-stage edge separation appears as one or a few semi-circular areas that are less transparent than the glass, or sometimes very shiny looking. Over time, they can grow larger and join with other spots, until there's a noticeable effect all around the edge of the element.
Sometimes, it's difficult to distinguish separation from some types of fungus. Separation doesn't have any striations or spidery arms like many types of fungus, but not all fungi look like this. For example, I have a lens in the shop right now to determine if its rear element has a case of fungus or very widespread separation. If it's fungus on an external surface (as opposed to between elements), then there's a 50% chance that Dave at CRC can clean it up just fine. Most cases of separation that I've had really didn't affect IQ, but it bugs the heck out of me. I've returned one lens for separation (Planar 50/1.7), which is few in comparison with the numbers I've returned for fungus (3) or scratches on the glass (2). Of course, this doesn't include the ones that I've either damaged myself, or which have sprouted or separated when in my posession.
As far as what to do goes, I guess it depends on the value of the lens. In most cases, I think it's less expensive and far less aggravating to try to find another copy of the lens, even if it's relatively expensive. Of course, the ideal solution is to locate one in "as is" condition that has different 'challenges' than your particular case. I actually did this successfully for an old Vivitar Series 1 35-85mm/2.8 zoom that I carelessly scratched on the front element. I found a 'beater' for a really low price, had Dave swap front elements, sold the fixed one for a decent price, and used the crapped-out one for an experiment on the effects of paint ball impacts on protective filters. Win-win situation.
Cheers, Jim
Apr 18, 2011 at 06:15 AM
p.1 #6Problems with old lens elements
If trying DIY recementing, skip canada balsam and use a modern UV-curing optical adhesive. These allow infinite repositioning before setting so you can get the elements perfectly aligned without worrying if the glue will set too quickly. Edmund Optics sells adhesives like this, along with syringes to inject them with, and curing lights (though a UV flashlight would cure it fine too).
Apr 18, 2011 at 09:01 AM
p.1 #7Problems with old lens elements
jcolwell wrote:
I found a 'beater' for a really low price, had Dave swap front elements, sold the fixed one for a decent price, and used the crapped-out one for an experiment on the effects of paint ball impacts on protective filters. Win-win situation.
Cheers, Jim
Now that is way-better than shooting test charts...
Enjoy Amsterdam Jim, and don't forget about the photo shops I told you about near the rail station.
Regards,
Edd
I found a 'beater' for a really low price, had Dave swap front elements, sold the fixed one for a decent price, and used the crapped-out one for an experiment on the effects of paint ball impacts on protective filters. Win-win situation.
Cheers, Jim
Now that is way-better than shooting test charts...
Enjoy Amsterdam Jim, and don't forget about the photo shops I told you about near the rail station.
Regards,
Edd
Apr 18, 2011 at 09:05 AM
p.1 #8Problems with old lens elements
Hi Edd,
I'm back at home now. I didn't do any 'research' while in A'dam. Instead, I met an old friend from R'dam. We went to the Rijksmuseum and had dinner in a fine restaurant. I took along my new XZ-1. Talk about alternative.
Jim
I'm back at home now. I didn't do any 'research' while in A'dam. Instead, I met an old friend from R'dam. We went to the Rijksmuseum and had dinner in a fine restaurant. I took along my new XZ-1. Talk about alternative.
Jim
Apr 18, 2011 at 10:17 AM
p.1 #9Problems with old lens elements
Ed Sawyer wrote:
If trying DIY recementing, skip canada balsam and use a modern UV-curing optical adhesive. ...
Yes, thought about this way. Problem is, that I would not be able to reopen the lens-element once more. Or are there easy ways to solve the adhesive?
I think I will make some mistakes in my first recementing experiments, so a reversible way is better for me. Probably I will try different ways of recementing with this cheaper lenses.
If trying DIY recementing, skip canada balsam and use a modern UV-curing optical adhesive. ...
Yes, thought about this way. Problem is, that I would not be able to reopen the lens-element once more. Or are there easy ways to solve the adhesive?
I think I will make some mistakes in my first recementing experiments, so a reversible way is better for me. Probably I will try different ways of recementing with this cheaper lenses.
Apr 18, 2011 at 03:44 PM
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p.1 #10Problems with old lens elements
Have a 35-85 Series1 that seems to have a coating problem in addition to fungus, which is probably also a coating problem. Sharp at 5.6 not sharp at 2.8 but probably not sharp there ever. Mostly I get flare. Took it apart, tried to clean it, got it pretty good and left it. Now shoot something else. Haze and fungus don't usually affect resolution but they cause flare.
Apr 18, 2011 at 03:53 PM
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p.1 #11Problems with old lens elements
I should probably add, the lens is still sharp and photos look good if you can keep it shaded. Probably outperforms a lot of new stuff at 5.6 and 8 under low flare conditions.
Apr 18, 2011 at 06:44 PM
p.1 #12Problems with old lens elements
Thank you gents for your input.
Let me ask you a more specific question though. When looking thru a lens doublet and wiggling it a bit, that person claims he sees a sort of a shimmer like in air above hot asphalt pavement. Now, at a face value of it, that sounds to me like changes in refractive index of the medium. That made me wonder about the cause. The first thing I thought about was doublet separation and misalignment. Unfortunately, I have no direct experience with observing any of those phenomena.
Let me ask you a more specific question though. When looking thru a lens doublet and wiggling it a bit, that person claims he sees a sort of a shimmer like in air above hot asphalt pavement. Now, at a face value of it, that sounds to me like changes in refractive index of the medium. That made me wonder about the cause. The first thing I thought about was doublet separation and misalignment. Unfortunately, I have no direct experience with observing any of those phenomena.
Apr 18, 2011 at 07:07 PM
p.1 #13Problems with old lens elements
Peter - would need to see examples, shimmering could be just interference patterns possibly too (which could also be related to separation).
Re: UV adhesives: They do have one that is releasable, it can be undone with acetone.
Re: UV adhesives: They do have one that is releasable, it can be undone with acetone.
Apr 19, 2011 at 06:49 AM
p.1 #14Problems with old lens elements
...Re: UV adhesives: They do have one that is releasable, it can be undone with acetone.
Yes, the NOA 107, but it is only reccomended for short time glueing. With the Canda Balsam I could make the glueing, and decide afterwards if it is perfect for longer time or if the recemmenting is bad and I should open it again.
But I have to admit, that the working with the hot lenses and Canada Balsam seem not very easy. Probably I start tests with the balsam, and go afterwards and buy the UV curing glue.
Yes, the NOA 107, but it is only reccomended for short time glueing. With the Canda Balsam I could make the glueing, and decide afterwards if it is perfect for longer time or if the recemmenting is bad and I should open it again.
But I have to admit, that the working with the hot lenses and Canada Balsam seem not very easy. Probably I start tests with the balsam, and go afterwards and buy the UV curing glue.
Apr 19, 2011 at 07:53 AM
p.1 #15Problems with old lens elements
undoing the balsam is going to be more work and trouble than undoing the releasable UV glue.
Apr 19, 2011 at 11:51 AM