What could this lens damage be?

Marcelo Paniagua · Sep 13, 2021

Just got a large format lens from the bay, Lens have a strange damege/issue. It has a yellowish area on the front element. The area is transparent but yellowish, Not sure about image impact yet. Was wondering if any you could provide any info about what happened to the lens? The area is only visible at a certain angle.

Dan Fromm · Sep 13, 2021

Separation. The cement holding two elements together is failing.

On another subject, could you buy some e-books from the educal.com.mx libreria in Mexicali for me?

Marcelo Paniagua · Sep 13, 2021

Would it get worse over time? What effect could it have on lens?

Marcelo

AgX · Sep 13, 2021

At this very patch both lens elements behave as being uncemented. Thus having a normal (in air) reflection, whereas in the cemented part this reflection is strongly reduced (because the media differ much less in refraction than glass vs. air)

Dan Fromm · Sep 13, 2021

Marcelo Paniagua said:
Would it get worse over time? What effect could it have on lens?

Marcelo

Well, the lens won't fall apart but image quality may suffer but it may not. Kodak sold an elaborate cemented negative diopter for the 25/1.4 Cine Ektar. The diopter reduces the prime lens' focal length to 15 mm. I have one with terrible separations that make very visible Newton's rings. It is unusable, footage shot with it comes out with red and blue stripes like those Newton's rings. I also have a 58/5.6 Grandagon with severe separations, rings of fire around the periphery of both cells, slivery spots in the center of the rear cells. It shoots very well.

For curiosity, what is the lens and, if Rodenstock or Schneider, what is its serial number? Some vintages of both makers' lenses suffer severely from separations. Poor choice of synthetic cement.

If you got a great deal on the lens, try it out. Otherwise, send it back. I don't know what it is but there are sure to be other functionally equivalent lenses -- same design type, focal length, maximum aperture and coverage -- out there.

Cheers, good luck,

Dan

Marcelo Paniagua · Sep 13, 2021

Lens is a Caltar II Type S 135mm. Serial number is 8813058 It is supposed to be a Rodenstock, but could be wrong.

Marcelo

AnselMortensen · Sep 13, 2021

I was going to ask if it was a Rodenstock.
Early Rodenstock Sironars ( pre "-N", etc) had major issues with separation due to the adhesive used.
Return it.

Marcelo Paniagua · Sep 13, 2021

Will return it. It was about$200 so I guess it doesnt worth the risk

AgX · Sep 14, 2021

I do not see an issue. And so far such was not reported here on similar cases.

AgX · Sep 15, 2021

Is that gap infinitely small, then just a stronger reflection will occur. However, is the gab wider, then a parallel shift of rays may accur. Thus such a complete airgap may be desired in design. For instance to come closer in effect of a spherical optic to an asherical one.

Bob S · Sep 15, 2021

Marcelo Paniagua said:
Lens is a Caltar II Type S 135mm. Serial number is 8813058 It is supposed to be a Rodenstock, but could be wrong.

Marcelo

If it is a Rodenstock it’s from 1973.

250swb · Sep 16, 2021

It's so obvious it should have been declared in the eBay auction. Send it back and don't let them tell you you Should have seen the damage in the auction photos, there are often all sorts of reflections in pictures of lens elements and it could have easily been mistaken for such.

Marcelo Paniagua · Sep 17, 2021

Send lens back. And yeah, seller tried to convince that it was apparent on photo but no, it wasn't visible on photo and not mentioned. Seller gave me full refund so on the look for another one.

Marcelo Paniagua · Sep 17, 2021

Thanks for the help glad I asked.

Kino · Sep 17, 2021

I maintain that lens separation can occur when a lens is shipped in an unpressurized and unheated cargo bay of an airplane. It happened to me when I sent a set of cine lenses to China and every one of the lenses (admittedly older lenses) separated before they arrived to the buyer.

If you have a valuable lens you must ship via air cargo, you would be well advised to go to purchase an inexpensive, sealed case in which to ship it.

Something like this: https://www.harborfreight.com/1800-weatherproof-protective-case-small-64550.html
or this: https://www.jensentools.com/pelican...mOITIKY9pSCsIKBYmYeuNbDRSCj8_RoBoCWIkQAvD_BwE

AgX · Sep 17, 2021

Cargo bays in jet airliners and in jet air-freighters are pressurized.

Even a very low air pressure cannot induce lens-element seperation.*

(*One may argue on residential solvent in the balsam outgassing under low pressure, but I find this very far fetched.)

AgX · Sep 17, 2021

However this idea of a solvent might explain those cases of splattered lens element separation without connection to the air. But here one may argue on just a vacuum instead.

Nodda Duma · Sep 18, 2021

Extreme temperature changes and/or thermal shock cause bond joint failure due to large differences in thermal expansion coefficients between crown and flint. Kino’s lenses were ruined when the cargo bay, which is unheated, dropped down to ambient temps at 35,000 ft.

Air pressure has nothing to do with it.

AgX · Sep 18, 2021

Nodda Duma said:
Kino’s lenses were ruined when the cargo bay, which is unheated, dropped down to ambient temps at 35,000 ft.

Cargo bays at jet airliners and the cargo part of jet airfreighters are temperaturized. At the latter at least above freezing (+7°C is stated).

Nodda Duma · Sep 18, 2021

AgX said:
Cargo bays at jet airliners and the cargo part of jet airfreighters are temperaturized. At the latter at least above freezing.

They see a rapid enough of a change in temperature to be considered thermal shock. That is one of the two causes of separation, the other being temperature extremes.

AgX · Sep 18, 2021

Having a camera at home at 20°C and then just going into the garden at 7°C would be a stronger shock. Even stronger than loading the camera at 40°C into the belly of a freighter which then climbs into the cold sky, due to the isolating air volume in the freighter which first must cool down itself..

Nodda Duma · Sep 18, 2021

If you say so

Kino · Sep 18, 2021

Nodda Duma said:
Extreme temperature changes and/or thermal shock cause bond joint failure due to large differences in thermal expansion coefficients between crown and flint. Kino’s lenses were ruined when the cargo bay, which is unheated, dropped down to ambient temps at 35,000 ft.

Air pressure has nothing to do with it.

Either way, an inexpensive case would be a very good idea when shipping valuable lenses.

It is more valuable to be practical, than exactly right.

Nodda Duma · Sep 18, 2021

Kino said:
Either way, an inexpensive case would be a very good idea when shipping valuable lenses.

It is more valuable to be practical, than exactly right.

As a lens designer, I’m trying to provide insight into the cause of lens separation in older optics. That insight — like any insight provided by knowledge and experience — helps lead to practical solutions.

Education, not ego, is at play here.

AgX · Sep 18, 2021

But you did not bring an argumemt against what I said above.

I only took that +7°C, as that figure was given for airfreighters. But we can use much lower temperatures. People in lets say Canada too step out of their heated homes with their cameras into -30°C or less without their lenses breaking: a fall by 50Kelvin within seconds. At least I do not know of such reports. And you likely will not sent a camera or lens just with a tag at a string. Instead you will pack it with padding in a cardboard box. Then add the slow fall in temperature in the plane. Yes, a front element will still be affected earlier than a element cemented to it.

But instead of any thermal shock, absolute difference in temperature, with lens elements of glass with different expanding coefficient is much more plausible to me.

You had it about old lenses affected.
But are not modern glues more brittle than natural resins? I don't know, but I wonder.

What could this lens damage be?

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