Usable Eye Relief (spartan method) (1 Viewer)

[Anderlfs]

hi all, I have learned a lot since arriving on this forum a few days ago. I'm currently trying to measure the "usable eye relief" of my Meade CanyonView 8x42 because despite having only 14mm of specified eye relief, I can see the entire FOV on It wearing eyeglasses. My purpose is to be able to better compare with binoculars that I cannot test. I would like some feedback on whether what I did is valid. I read in some topics that there is even Dutch equipment designed to measure this, but as I don't have access, I'm trying to do It in a rustic way, just to get an idea of the measurement. Therefore, I started with the theory illustrated below.

I basically took a piece of paper with a marking on It and something stiff and thin like a metal ruler. Then I measured the difference and discounted the eye relief specified by the manufacturer.


If the method is OK, the usable eye relief of this binoculars should be around a mere 10mm. I believe I can use it due to the fact that I wear rimless glasses, bringing the lenses closer to the eyes.


I appreciate any feedback.
Thanks in advance.

 

[Canip]

The basic question for me is: do you trust the manufacturers‘ spec for the technical eye relief (you could sometimes be surprised …)?

If yes, your spartan method seems appropriate to me to get to the „usable“ eye relief. Measure as precisely as possible the distance from the rim of the folded eyecup down to the eyepiece lens and subtract the resulting number of mm from the technical eye relief number. Finished!

If the manufacturers spec seems dubious, things are way more complicated. That‘s why I use a special device called dynameter to measure things like eye relief and diameter of the exit pupil etc.

 

[WJC]

hi all, I have learned a lot since arriving on this forum a few days ago. I'm currently trying to measure the "usable eye relief" of my Meade CanyonView 8x42 because despite having only 14mm of specified eye relief, I can see the entire FOV on It wearing eyeglasses. My purpose is to be able to better compare with binoculars that I cannot test. I would like some feedback on whether what I did is valid. I read in some topics that there is even Dutch equipment designed to measure this, but as I don't have access, I'm trying to do It in a rustic way, just to get an idea of the measurement. Therefore, I started with the theory illustrated below.
View attachment 1570116
I basically took a piece of paper with a marking on It and something stiff and thin like a metal ruler. Then I measured the difference and discounted the eye relief specified by the manufacturer.
View attachment 1570118View attachment 1570119

If the method is OK, the usable eye relief of this binoculars should be around a mere 10mm. I believe I can use it due to the fact that I wear rimless glasses, bringing the lenses closer to the eyes.
View attachment 1570120

I appreciate any feedback.
Thanks in advance.

Are you wanting to measure EYE RELIEF or the width of the exit pupil? Your photo makes it appear to be the latter.

 

[Gijs van Ginkel]

Canip post 2,
For our measurements of eye relief, I use a Ramsden dynameter (designed and made by the Netherlands optical company Bleeker, the optical engineer who has worked for that company later became head of the optical workshop of the Utrecht Universities workshop and I received it from him) and that measures the eye relief as the distance from the surface of the exit lens of the eyepiece lens to the observers eye. In my opinion that is the only correct method, since the thickness of the rims of the eyecup can vary quite a bit. With this dynameter one can also measure directly the diameter of the exit pupil.
Gijs van Ginkel

 

[Canip]

Gijs (post # 44),
What you are measuring is what I call the "technical" eye relief, measured from the lens surface. This is in optics terms the "correct" way to measure eye relief, but for people wearing glasses the result is not necessarily a very useful number. I measure from the rim of the eyecup to get something called "usable" eyerelief; in my experience, the thickness of the eyecup rim does not vary much between different samples of the same binocular model.
I use a dynameter made by German company Trioptics, member of the Jenoptik group.

 

[Gijs van Ginkel]

Canip, post 5,
I did understand from your previous posts what you are measuring and how you are measuring it, but the producers publish the eyerelief the way I described it and technically that is in my view correct. I would describe your method as practical eyerelief, since you take into account the thickness of the rim of the eyecup, but since there were questions by some about the correctness of the values by the binocular producers I thought that it might it may be helpful to describe the differences. As far as our dynameter is concerned: it is described extensively in F. Kohlrausch "Lehrbuch der praktischen Physik"sechzehnte Auflage, 1930, page 361. I received that textbook from one of the directors of Bleeker optical company "Nedoptifa".
(Dr. Bleeker shared patents with Prof. Frits Zernike with regard to the development of phase contrast microscopy for which he received the Nobelprize in 1953).
Gijs van Ginkel

 

[Maljunulo]

Canip, post 5,
I did understand from your previous posts what you are measuring and how you are measuring it, but the producers publish the eyerelief the way I described it and technically that is in my view correct. I would describe your method as practical eyerelief, since you take into account the thickness of the rim of the eyecup, but since there were questions by some about the correctness of the values by the binocular producers I thought that it might it may be helpful to describe the differences. As far as our dynameter is concerned: it is described extensively in F. Kohlrausch "Lehrbuch der praktischen Physik"sechzehnte Auflage, 1930, page 361. I received that textbook from one of the directors of Bleeker optical company "Nedoptifa".
(Dr. Bleeker shared patents with Prof. Frits Zernike with regard to the development of phase contrast microscopy for which he received the Nobelprize in 1953).
Gijs van Ginkel

I didn’t realize that a Nobel Prize was awarded, but I do know that optical phase-contrast microscopy was/is a really big deal.

 

[Anderlfs]

Canip, post 5,
I did understand from your previous posts what you are measuring and how you are measuring it, but the producers publish the eyerelief the way I described it (…)

Gijs,
I was almost certain you were measuring the same way as Canip, as I read an article of yours where the GPO Passion ED 8x32 Eye Relief measured the same 13mm he found, even though the manufacturer specifies 16mm.
Anderson.

 

[Gijs van Ginkel]

Maljuno, post 7,
On November 3, 2023 Groningen University celebrated the 75-th anniversary of the Nobel Prize of Prof. Zernike, which he received in 1953 for the development of phase contrast microscopy. It was celebrated by an international symposium during which also a lecture was dedicated to Dr. Caroline Bleeker and her company Nedoptifa. Since I had written a 200 page biography of Dr. Bleeker en her company I was invited to give a lecture during the symposium about Dr. Bleeker and her company. Dr. Bleeker knew Prof Zernike quite well, since he visited Utrecht University regularly to meet the head of the Utrecht Physiscs faculty Prof. L.S. Ornstein who came to Utrecht after being assistent professor in Groningen, where he had been friends with Prof. Zernike (the story goes that he even came by bike from Groningen to Utrecht!). During these visits in Utrecht he also got to know Dr. Bleeker, who was a PhD student at that time in Utrecht.
After her PhD work Dr. Bleeker started a company that constructed scientific instruments and Prof. Zernike stimulated her to also produce optical instruments among others microscopes. He even donated a small amount of money to help the start of the company..
Until now this story has seemingly nothing to do with binoculars, I will help: Dr. Bleekers company also made a series of different binoculars all porros: 6x24, 8x24, 6x30, 7x50 and a telescope for astronomy. If you are interested: the Bleeker biography is als available in digital form on the WEB-site of the Faculty of Physiscs magazine Fylakra (in Dutch).
The printed 200 page Bleeker biography I have written is for sale by Jan van Daalen , House of Outdoor, Maarsen., The Netherlands. I am not involved in these sales so you have to approach Jan if you are interested.
Gijs van Ginkel

 

[Patudo]

What I'd love to know (but can find nothing about) is to what extent phase coatings have improved since their introduction, and how much R&D goes into them compared to other aspects of binocular design. Are P coatings today better at bringing wavelengths back into phase than those used a decade or 20 years ago? And are such effects discernible?