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Nikon 82ED Eyepiece Glass (1 Viewer)
- Thread starter spimly
- Start date
Kevin Purcell
Well-known member
You don't use ED glass in eyepieces only in objectives.
You do use some exotic glasses (that have special dispersion) like Lanthanum Crown (LaK) in EPs. Hence the marketing talk about Lanthanum eyepieces.
AFAIK, Nikon doesn't talk about the components glasses used in their EPs but I suspect they may use LaK elements.
You do use some exotic glasses (that have special dispersion) like Lanthanum Crown (LaK) in EPs. Hence the marketing talk about Lanthanum eyepieces.
AFAIK, Nikon doesn't talk about the components glasses used in their EPs but I suspect they may use LaK elements.
I will be the first to admit I am ignorant in such matters but others in the following thread make a case for the usefulness of ED in the ep's:
Are these not valid reasons why ED glass in ep's would be beneficial? Or does Lanthanum glass provide most (all?) of the ED qualities? Maybe Lanthanum glass is ED glass??
As I said, I am ignorant of such things but I am curious!
Kevin Purcell
Well-known member
That thread does not even claim that ED glasses are used in those EPs. They're not.
LaK is not an ED glass.
Search for and read the thread where Henry Link and I explain Abbe number and what ED really means.
LaK is not an ED glass.
Search for and read the thread where Henry Link and I explain Abbe number and what ED really means.
I was reading a link within that link that was talking about bins but seems generic. Specifically:
henry link Saturday 1st November 2008, 11:24
... Using ED glass in the objective appears to improve things, but does not seem to be a complete fix for binoculars like that, while even very cheap Porros with simple cemented doublet objectives and no focusing element can have very little lateral color except toward the edge where you expect it in the eyepiece.
... Using ED glass in the objective appears to improve things, but does not seem to be a complete fix for binoculars like that, while even very cheap Porros with simple cemented doublet objectives and no focusing element can have very little lateral color except toward the edge where you expect it in the eyepiece.
I'll search for the discussion you mention because this seems interesting! Thanks for the info about the Lanthanum glass.
mikefreiberg
Well-known member
Kevin,
What does laK glass do that makes it different than extra-low disperison glass? Thanks!
Best,
Mike Freiberg
Nikon Birding Market Specialist
Kevin Purcell
Well-known member
Just has different optical properties especially different dispersions and different refractive index.
To make a well corrected EP (or scope) you need glass of different properties (dispersions) so you can cancel out the CA over the whole design. These La glasses give you a bit more flexibility. Same with lower dispersion and lower refractive index ED glasses or CAF2 but you'll only ever find those in long focal length objectives.
La glasses they have a high refractive index with middling Abbe number (medium to low dispersion). Good for making compact strong (short focal length) lenses with a matching material with opposite dispersion as needed in an EP.
But doesn't have an so low dispersion that the Abbe Number > 90 so it's not ED.
Lanthanum glasses replace similar barium glasses with lower refractive indicies but similar Abbe number.
http://www.edmundoptics.com/images/technical_library/article329_figure1_large.gif
The typical ED glasses are in the bottom left corner. The Lanthanum glasses above the Barium glasses (the ones that they typically replace) in the middle of the chart. In addition to Lanthanum crown, LaK, you can also get lanthanum flint glasses (LaF and LaSF "heavy flint") so you can make better achromatic doublets or APO triplets.
Simple paper on La glases: http://www.austincc.edu/photo/pdf/lanthanum.pdf
Or for a quick overview on glasses
http://www.edmundoptics.com/technical-support/optics/optical-glass/?&viewall
with the typical Abbe plot of refractive index versus Abbe number.
To make a well corrected EP (or scope) you need glass of different properties (dispersions) so you can cancel out the CA over the whole design. These La glasses give you a bit more flexibility. Same with lower dispersion and lower refractive index ED glasses or CAF2 but you'll only ever find those in long focal length objectives.
La glasses they have a high refractive index with middling Abbe number (medium to low dispersion). Good for making compact strong (short focal length) lenses with a matching material with opposite dispersion as needed in an EP.
But doesn't have an so low dispersion that the Abbe Number > 90 so it's not ED.
Lanthanum glasses replace similar barium glasses with lower refractive indicies but similar Abbe number.
http://www.edmundoptics.com/images/technical_library/article329_figure1_large.gif
The typical ED glasses are in the bottom left corner. The Lanthanum glasses above the Barium glasses (the ones that they typically replace) in the middle of the chart. In addition to Lanthanum crown, LaK, you can also get lanthanum flint glasses (LaF and LaSF "heavy flint") so you can make better achromatic doublets or APO triplets.
Simple paper on La glases: http://www.austincc.edu/photo/pdf/lanthanum.pdf
Or for a quick overview on glasses
http://www.edmundoptics.com/technical-support/optics/optical-glass/?&viewall
with the typical Abbe plot of refractive index versus Abbe number.
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