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Customising the focussing wheel & eyecups of a modern Roof binocular (1 Viewer)

Stephen Prower

Well-known member
Summary: I describe user modifications to a new binocular with the object of: 1) Improving the feel of the focussing wheel; 2) Locating the eyes consistently at the point of eye relief


I have started to customise a modern Roof binocular that has adjustable eyecups. I have so far achieved two improvements to 'ergonomic' aspects of the performance of the binocular that disappointed me. (1) The focussing wheel after an hour or so became uncomfortable to use. (2) I was not fully happy with the view through the binocular. I suspected that I was not locating the eyes consistently at the point of eye relief.

I attach a photo of how I modified the focussing wheel and eyecups.

In case it is useful to anybody, I go on below as I have said to describe and explain the modifications.

I apologise if I sometimes repeat what I have said in previous posts on the Forum on the subject of using bicycle inner tube to bulk out the width of binocular eyecups.


Changing the feel of the focussing wheel

The edge of the focussing wheel of the Roof had a coarse 'grippy' rubber surface pattern. It became unpleasant to use after half-an hour or so's birdwatching. It also on one occasion caused the end of my finger on the wheel to go numb.

I therefore, as I have done before with old Porros, cut a section of bicycle inner tube, and sleeved it over focussing wheel.

The inner tube that I used was an ordinary--in Britain--Butyl rubber tube sized to fit a mountain bike tyre of 2.125 inch maximum section.

A tube made out of thinner rubber, or a tube sized to fit a tyre of 2.3 inch maximum section (which seems to be the next common size up), would probably have fitted more easily.

I don't report the result of a long term test. But the inner tube seemed to do the trick. The focussing wheel became more comfortable to operate, while at the same time continuing to provide a good grip.


Locating the eyes at the point of eye relief

A binocular should naturally come to the eyes with the eyes located at the point of eye relief.

When the binocular is thrown to the eyes, the location of the eyes above the ocular lens is not only determined by the elevation of the eyecups, but also by the most comfortable fit of the binoculars to the face as determined by the width of the eyecups.

In order to achieve a consistent location of the eyes at the point of eye relief, one must therefore match the figures of the elevation and the width of the eyecups individually for each user.

My method of doing so is 'Suck it and see'.

So I tried increasing the diameter of the eyecups by sleeving over them a doubled over section of inner tube sized to fit a mountain bike tyre of 2.5 inch maximum section. The inner tube increased the diameter of the eyecup from 40mm to 43mm, which I know from experience to be a comfortable diameter for me.

Ordinarily I would then have gone on to try different figures of the elevation of the eyecups, and when I got a good result for a particular figure, have frozen the eyecup in position with a rubber band of suitable width and thickness cut from more inner tube.

But I found that with the eyecups fully extended, I seemed to have hit the spot. I was already satisfied with the view.


Stephen
 

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  • IMG_2845 Modified focus wheel & Eyecups- S.jpg
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Stephen Prower

Well-known member
What is the binocular?
Maljunulo

I haven't named the binocular, because I hoped to start an 'ergonomic discussion', rather than 'optical comparison' thread*, but it's a SvBony SV202 8x32 ED


Stephen


* Eg I was surprised that adding just 3mm of extra width to the eyecups was sufficient to turn a disappointing view into to a good one. Binastro has commented that for binoculars, such as 7x35 extra wide angle Porros, that have very short eye relief, it is necessary to locate the eyes exactly at the point of eye relief. But the SvBony has a normal amount of eye relief
 
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Stephen Prower

Well-known member
Edmund

I don't wear spectacles (eyeglasses?).

The answer to your question has to be personal, but I give eyecups a rounded edge by using doubled over inner tube for the final bulking out layer (See photo for example).

The diameter of the rounded edge for a 40mm wide eyecup would be about 2 to 3mm*.

Such an edge is not soft, but it supplies sufficient comfort to me once I have got the width of the eyecups right.


Stephen


* The diameter might be more, but at 40mm width of eyecup, I am working close to the 'stretch to fit' limit of my stock of discarded bicycle inner tubes. I totally lack tubes to fit a tyre of more than 2.35 inch maximum section
 

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  • IMG_2785 Modified eyecup on 8x30 Porro 2.jpg
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Stephen Prower

Well-known member
Update:

I have now completed the customisation of the SvBony 202 8x32 ED. I attach a photo.

1) Rainguard: The supplied rainguard no longer fitted after I increased the width of the eyecups by 3mm. I therefore made a replacement. I used .3mm plastic sheet cut from a milk bottle skinned on either side by duct tape.

The new rainguard also improves upon the supplied rainguard by being QD (Quickly detachable).

2) Wings: I added 'fold down' wings to the eyecups. The wings are cut to fit my face. They fold down easily should I want for whatever reason to get them out of the way*.


Stephen

* The purpose of winged eyecups is twofold. The first is to shut out sidelight. The second is to stop the user from being distracted by objects or stimuli located outside the field stops that still remain within the radius of view of the user's peripheral vision.

The point of 'fold down' winged eyecups is that one may not always want to lose peripheral vision when using a binocular.

For instance by virtue of the reflex attraction of the eyes in peripheral vision to a fast moving object, the user may be alerted to the approach of a bird before it actually appears in view through his/her binocular
 

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  • IMG_2853 Fully customised SvBony 202 8x32 ED.jpg
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Dr. K

Well-known member
United States
I am also a fan of wings on eyecups, so long as they can be easily moved out of the way... My swaro eyecups can slide down the (fully extended) eyecups so that at their highest point they block out everything, and at their lowest they help a little with sidelight but don't significantly detract from my peripheral vision and situational awareness (occasionally very important when birding in remote parts of a city park). Congrats on finding a solution for your application.
 

Stephen Prower

Well-known member
Dr K.

Thank you! Nothing to do with birdwatching, but my situational awareness came too late the other day. Riding my bike I saw the car in an over the shoulder 'Life saver' glance just as we collided. I picked up a bad gash to the leg, but am now nearly recovered. I gather remote parts of a city park can sometimes, like the dangerous junction where I had the accident, be bad places!

Stephen
 

Dr. K

Well-known member
United States
Dr K.

Thank you! Nothing to do with birdwatching, but my situational awareness came too late the other day. Riding my bike I saw the car in an over the shoulder 'Life saver' glance just as we collided. I picked up a bad gash to the leg, but am now nearly recovered. I gather remote parts of a city park can sometimes, like the dangerous junction where I had the accident, be bad places!

Stephen
Yikes! Glad that you’re on the mend. Cheers.
 
ZEISS. Discover the fascinating world of birds, and win a birding trip to Columbia
ZEISS. Discover the fascinating world of birds, and win a birding trip to Colombia
ZEISS. Discover the fascinating world of birds, and win a birding trip to Colombia

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