Re: One way to fix lens separation
Quote:
Originally Posted by
Dan Fromm
We both missed another manifestation. I once bought a 16/2.5 Zeiss Luminar -- yes, this is a large format lens -- that appeared to have been baked while vertical. There was balsam puddled around the front element and visible voids between the cemented elements.
Actually the Luminars like the MComponons and other lenses designed for true macro work would work on many different formats. If I remember correctly, when we sold the Luminars the 16mm on a 45 Technika gave over 20x magnification. Sold a lot of them as both the Zeiss Voightlander and the LInhof distributor until stocks were depleted.
Re: One way to fix lens separation
Quote:
Originally Posted by
Steven Tribe
NO - for Canada Balsam separation. The balsam never becomes a homogeneous solid, so separation is gradual. Some solids are deposited , which can give a general yellowing to the edges.
I don't understand this. Ok, the canada balsam may not be a solid. But the glass is. So you have separation or not. The newton rings are not dependent on how slow the separation evolves, only on how far there is separation with air between the elements.
Re: One way to fix lens separation
There is really very little separation with air spacing development when Canada balsam begins to break down. There are some some small areas close to the edge but by then there is an opaque sandwich of granular ex-balsam.
I have never tried to redo a complex modern lens, but have had a number of the Newton ring sufferers through my hands. The UV glue remains clear, in one piece and the connection with a glass surface is lost over a good percentage of the lens. I don’t know whether the interference comes from the increased gap between the lens surfaces proper, or the gap between the glue (which acts like an extra plastic lens) and “uncovered” lens surface.
The distance between the separate rings (or the width of the rainbow lines) is related to the wavelength and distance between the two surfaces. But others will correct me as my optics was a very long time ago!
Re: One way to fix lens separation
Quote:
Originally Posted by
Steven Tribe
There is really very little separation with air spacing development when Canada balsam begins to break down. There are some some small areas close to the edge but by then there is an opaque sandwich of granular ex-balsam.
Ok, so you mean that when canada balsam let go, it doesn't really forms air space but it kind of swells and its optical properties change to opaque.
I did have 2 lenses with canada balsam separation and they had some kind of "iridescent glow" over a large surface, starting from the edge. Don't know how to describe it better. Different from newton rings. Might have a photo of it somewhere.
Re: One way to fix lens separation
Hey Steven,
It’s due to the newly formed airgap. The index difference between adhesive and glass is not significant enough to form visible Newton rings.
-Jason
Quote:
Originally Posted by
Steven Tribe
There is really very little separation with air spacing development when Canada balsam begins to break down. There are some some small areas close to the edge but by then there is an opaque sandwich of granular ex-balsam.
I have never tried to redo a complex modern lens, but have had a number of the Newton ring sufferers through my hands. The UV glue remains clear, in one piece and the connection with a glass surface is lost over a good percentage of the lens. I don’t know whether the interference comes from the increased gap between the lens surfaces proper, or the gap between the glue (which acts like an extra plastic lens) and “uncovered” lens surface.
The distance between the separate rings (or the width of the rainbow lines) is related to the wavelength and distance between the two surfaces. But others will correct me as my optics was a very long time ago!