• Welcome to BirdForum, the internet's largest birding community with thousands of members from all over the world. The forums are dedicated to wild birds, birding, binoculars and equipment and all that goes with it.

    Please register for an account to take part in the discussions in the forum, post your pictures in the gallery and more.
ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

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.
 
Last edited:
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.
Canip
 
Would be great if more people would read Holger Merlitz‘ binocular book (unfortunately still only available in German 😞)
 
Warning! This thread is more than 2 years ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.

Users who are viewing this thread

Back
Top