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Test for Phase-Corrective Prism Coatings (1 Viewer)

Today I received my new pair of pristine condition Leitz 7x35 BA binoculars from @DLedig (thanks, Dave). They are amazingly bright and clear for a 32-year old binocular! This pair dates from 1986 (s/n 964920) and I was curious whether they might have received one of the early phase-correction coatings that were just being developed in the late 1980s.

So I decided to perform the polarizer test: Against a white LCD laptop screen, look through the objective end of the binoculars while wearing sunglasses with polarized lenses. You can also use a polarizing filter for a camera lens if you don't have polarized sunglasses.

When you rotate the binoculars or the polarizing lens, you'll see one of two things: If half the view goes dark blue/black and the other half is clear, the binocular does NOT have phase-correction coatings on its prism.

If the view stays mostly the same with only a faint line across the middle, the binoculars DO have phase-correction coatings.

In my case, I'm sorry to report that my Leitz 7x35 BA do NOT have phase-correction coatings. For comparison, I also tested my modern Zeiss Conquest HD 10x42 as well as my Zeiss TL 10x25. Both of them clearly do have phase-correction coatings.

This test seems an unmistakable way of determining whether or not your binoculars have phase-corrective coatings.
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phase-correction coatings on its lenses.
Just to be sure that we talk about the right thing here: phase correction coatings are never applied to the lenses, only to the roof prisms.
Btw: the test you describe in my experience often leads to inconclusive results.
Would be great if more people would read Holger Merlitz‘ binocular book (unfortunately still only available in German 😞)
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