Is close focusing ability in a binocular REALLY necessary (1 Viewer)

Tringa45 said:

Lee,


I have occasionally used my 8x33 Kowa Genesis for watching butterflies and have just tried it at its minimum focussing distance of 1,5 m. I had to reduce the IPD from 63 mm to 58 mm but it was nevertheless very uncomfortable trying to merge the images. As others have pointed out, I think the vast majority is well served by a close focus of 3 m as on the latest Swarovski CLs and SLCs. In 15 years of use of a 7x42 SLC (4 m Close focus) I could count the situations on the fingers of one hand in which I would have wished for less.

John

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Yes, the problem of close focus is not just "focusing the image", there will be excessive parallax making it very hard for the brain to fuse the left and right images. See US Patent No. 9,746,660 for a modern solution

-Omid

Close focus ability for me generally ADDS to the enjoyment of using a binocular, but its not essential. Between 2-3 meters is great.

I've got a few bins for astro purposes that can't focus on the bird feeder when I'm near the window. They don't get used that often these days.

There probably is less of a market share for a binocular that has 'perceived shortcomings' with regards to the ongoing spec war. A simple solution is to buy used binoculars that DO meet one's specs.... simpler eyepieces, etc.

Wouldn't it be great to go back to the days of sub 15mm eye relief, wide angle views, and nothing that focuses under 3 meters? Plus, throw out any IPD below 57mm...

If all bins conformed to those specs I wouldn't able to use ANY of them. There's a lot of bins out there for the unsatisfied many, that will meet their specs. There's very few, relatively speaking, that meet mine.

-Bill

Tringa45 said:

...Such extreme close focus either demands stronger focussing elements or increased travel thereof, which in both cases could be detrimental to correction of spherical and chromatic aberration.

John

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Hello John,

I recall that a physicist with a strong interest in optics wrote the same thing of chromatic aberration.

Happy bird watching,
Arthur

Tringa45 said:

Lee,

I did say a niche product and I think Arthur's, Canip's and Hermann's comments substantiate this. For butterfly watchers there are specialist products (reverse Porro) with a very narrow objective spacing, but I think the perceived pressure on manufacturers to offer close focussing of 1,5 m or less on roof prism binoculars is senseless, not only because of design, reliability and price considerations.

I have occasionally used my 8x33 Kowa Genesis for watching butterflies and have just tried it at its minimum focussing distance of 1,5 m. I had to reduce the IPD from 63 mm to 58 mm but it was nevertheless very uncomfortable trying to merge the images. As others have pointed out, I think the vast majority is well served by a close focus of 3 m as on the latest Swarovski CLs and SLCs. In 15 years of use of a 7x42 SLC (4 m Close focus) I could count the situations on the fingers of one hand in which I would have wished for less.

John

Click to expand...

Hi John

Next time you want to explore what close focusing can offer and are feeling uncomfortable with the images not merging, try this.

With the IPD set to 58mm as you describe. Close one eye or cover up the objective and look at the nearby subject through one side. Your eye and brain will perceive a normal circular image. Then open that eye and close the other and do the same with the other optical tube. Here you get another perfectly comfortable image. Now open both eyes and remind yourself you are seeing two perfectly comfortable images, don't concentrate on the extent of the overlap or tell yourself 'it shouldn't look like that', just look at the subject. I find that focusing solely on the subject and ignoring the strangeness of the overlap means I have no discomfort and can enjoy the subject.

As for the close focusing mechanism leading to unreliability or other failure, I have yet to encounter such a thing, and I can assure you that Greenshanks and Great Northern Divers look just as beautiful through binos with a 1.0 metre close focus as through ones with 3.0 metre close focus. They are the right shape, the markings are as they should be, the only difference being that I can use the 1.0 metre focusing binos to observe inter-tidal marine life in rock pools and enjoy another dimension to our days out on a Scottish coast. I am over retirement age and have been enjoying close focusing binos for many years and have yet to encounter any problems caused by this facility.

One reason why both me and Troubadoris value a close focus is that it is not infrequent that we find ourselves unexpectedly close to a subject as we come around a boulder or a bush or some other kind of cover. In Scotland it might be a Field Vole or Gold-ringed Dragonfly, in France it might be a water snake swallowing a fish or a huge green lizard (all real-life examples) and the last thing we want to do is to scare the creature off by both of us having to step back a couple of steps in order to focus our binos on the subject.

When close focusing is so useful for observing so many divergent forms of life I find it hard to understand how this can qualify as a 'niche interest'. To me a 'niche' suggests a very limited number of interests, perhaps only one.

Lee

Troubador said:

... just look at the subject. I find that focusing solely on the subject and ignoring the strangeness of the overlap means I have no discomfort and can enjoy the subject.

As for the close focusing mechanism leading to unreliability or other failure, I have yet to encounter such a thing, and I can assure you that Greenshanks and Great Northern Divers look just as beautiful through binos with a 1.0 metre close focus as through ones with 3.0 metre close focus.

Click to expand...

I too completely agree with Lee.

Instead, Hermann's first words to # 16 (like others) sound more like terrorism than good information! (Hermann, I'm kidding)
More reasonable here:

Hermann said:

What I forgot to write: I'm not talking here about a focusing distance of 8m, more something like 2-3m which IMO is quite reasonable for birdwatching.

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... but still unspecified, because 2m for 10x is very good, while 3m for 8x is already too far. We need to express a value that is proportionate to the magnification.

Magnification = virtual approach, and the key word is presbyopia.

The eye can be accommodated up to 7-8cm apart (3"), at ages under 7-8 years. Then it normalizes with maturity, up to 15-20cm (6-8"). And at a more mature age, over the 35-40 years, it is possible that it may become presbyopic. That is, the eye can no longer focus objects closer than 25cm (10" - is optical-ophthalmic standard).
In general, in a short time the presbyopic man will need reading glasses to read the newspaper at 35-40cm (14-16"), but also from 50-60cm (20-24") away.

Collecting both information, we see that a 10x binocular that focuses at 2.5m (8.2ft), has the power to virtually bring the user up to 25cm (10") away. Mathematics is simple. Therefore, 8x binoculars should focus at 2m (6.6ft) and 7x at 1.75m (5.7ft), etc.
This virtual focus distance (25cm - 10") is already "manna from heaven" for any presbyopite and also for others. But it is also very beautiful and much better to be approached virtually at 20cm (8 ") distance, to see the same objects with greater magnification and detail.

So, it would be possible and even clearer for everyone to talk about virtual focus distance, to include any magnification. Instead of naming an incomprehensible distance, because it is without reference (it is not a reproach, it is a proposal).

And so far, nothing wrong. I never had any optical quality problems, forcing my binoculars to focus closer than what they were designed for. Indeed, the Opticron technician set one of my roof-binocular 10x to focus closer than 2m (6.6ft), which means virtual 20cm (8"), when that model was designed to "focus at shorter distances of 3m (10ft)".
So, with my presbyopia, now I can also focus objects up to 1.8m (5.9ft) !!!

The real issue that separates the waters (and the masses) is the accuracy of the focus ring.
Unfortunately, if a fast focus is needed, to facilitate the observation of moving objects (birds, UFO, etc.), the price to be paid will be the loss of focus accuracy. This is not discussed, it is the reality of the facts.

But I believe this is the only factor that annoys-alienate users. And it will divide the waters forever. I know the solution, but I've never seen binoculars with that function for sale.

Rico70 said:

The real issue that separates the waters (and the masses) is the accuracy of the focus ring.
Unfortunately, if a fast focus is needed, to facilitate the observation of moving objects (birds, UFO, etc.), the price to be paid will be the loss of focus accuracy. This is not discussed, it is the reality of the facts.

But I believe this is the only factor that annoys-alienate users. And it will divide the waters forever. I know the solution, but I've never seen binoculars with that function for sale.

Click to expand...

If you mean a variable speed focuser that's fast a close distances and then slows down at medium to long distances that has been done in some binocular models made by Kamakura Koki, including the Brunton Epochs. I'm not sure if a variable speed focuser is used in any current binoculars, but it's available on a few spotting scopes, including the Nikon Monarch ED and a few models made by Kamakura including, as I recall, the Zeiss Gavia and Vortex Razor.

BF member Alexis Powell has long advocated for this feature.

Henry

Just thought some data might be interesting for you. I looked at the number of repairs and/or adjustments we've done to various 8x32 binocular families where the description of the work done related in some way to the focus mechanism. With that number I calculated a "score" based on the number of units sold of each family. Lower scores are better i.e. fewer units repaired/adjusted compared to the number of units sold.

Price sub-£100, close focus 5 metres, data over 7 years: score 0.00
Price sub-£150, close focus less than 2 metres, data over 10 years: score 0.50
Price sub-£200, close focus less than 2 metres, data over 10 years: score 0.25
Price sub-£200, close focus 3 metres, data over 5 years: score 0.00
Price sub-£350, close focus less than 2 metres, data over 5 years: score 0.05

So there is some correlation to price but also to close focus distance - that was a surprise to me to be honest.

Cheers, Pete

pete_gamby said:

Just thought some data might be interesting for you. I looked at the number of repairs and/or adjustments we've done to various 8x32 binocular families where the description of the work done related in some way to the focus mechanism. With that number I calculated a "score" based on the number of units sold of each family. Lower scores are better i.e. fewer units repaired/adjusted compared to the number of units sold.

Price sub-£100, close focus 5 metres, data over 7 years: score 0.00
Price sub-£150, close focus less than 2 metres, data over 10 years: score 0.50
Price sub-£200, close focus less than 2 metres, data over 10 years: score 0.25
Price sub-£200, close focus 3 metres, data over 5 years: score 0.00
Price sub-£350, close focus less than 2 metres, data over 5 years: score 0.05

So there is some correlation to price but also to close focus distance - that was a surprise to me to be honest.

Cheers, Pete

Click to expand...

Pete

Your analysis is in a way dependent on all other things being equal.
What if the extra versatility of the close focusing binos meant they were used more intensively, and the results of this increased workrate was more clear in the less expensive binos, reflecting the use of more economical materials .

Lee

henry link said:

If you mean a variable speed focuser that's fast a close distances and then slows down at medium to long distances that has been done in some binocular models...

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No, Henry. I wasn't referring to that, but it's certainly interesting.
I had already heard about it perhaps here or on CN, but I had never studied it in depth.
I think it is too complex a method, which can perhaps be applied (correct me if I'm wrong) to the most expensive models only.
No, I was thinking of something much simpler: binoculars with fast central focusing (to serve the birders) and at the same time the double adjustment of the diopter on the eyepieces (+/- 5D), to serve the sought-after accuracy with complete calm (precision long-range).

Among other things, this type would also be less expensive for the producer, because he would have to design and build only a single type of eyepiece and the barrel that accepts it.
Less processing, less differentiation, more profits.

I would sign up for such binoculars!

pete_gamby said:

Just thought some data might be interesting for you.

Click to expand...

Hi Pete, if you talk to me, the data seem to indicate that the most expensive binoculars break less than the others or that however it will be used more gently.

The cheapest 0.00 is consistent, as most of those models are robust Porro-prisms that are not used at 2m, but for far away.


But, why only 8x32?

Rico70 said:

No, Henry. I wasn't referring to that, but it's certainly interesting.
I had already heard about it perhaps here or on CN, but I had never studied it in depth.
I think it is too complex a method, which can perhaps be applied (correct me if I'm wrong) to the most expensive models only.
No, I was thinking of something much simpler: binoculars with fast central focusing (to serve the birders) and at the same time the double adjustment of the diopter on the eyepieces (+/- 5D), to serve the sought-after accuracy with complete calm (precision long-range).

Among other things, this type would also be less expensive for the producer, because he would have to design and build only a single type of eyepiece and the barrel that accepts it.
Less processing, less differentiation, more profits.

I would sign up for such binoculars!

Click to expand...

You're in luck if you can find this discontinued Steiner model.

https://www.allbinos.com/255-binoculars_review-Steiner_Wildlife_Pro_8x30_CF.html

The Kamakura variable speed focusing mechanism is very simple. It could be used in even the cheapest binoculars. I found the patent for it a few years ago. I'll see if I can find it again.

Henry

henry link said:

You're in luck if you can find this discontinued Steiner model.

Click to expand...

You are right !!! ... I completely forgot about the Steiner binoculars.
Which is a 'black sheep' anyway!

henry link said:

The Kamakura variable speed focusing mechanism is very simple. It could be used in even the cheapest binoculars. I found the patent for it a few years ago. I'll see if I can find it again.

Click to expand...

Thanks. Do you remember if it works well and if it can really resolve the issue?

Troubador said:

Hi John

Next time you want to explore what close focusing can offer and are feeling uncomfortable with the images not merging, try this.

With the IPD set to 58mm as you describe. Close one eye or cover up the objective and look at the nearby subject through one side. Your eye and brain will perceive a normal circular image. Then open that eye and close the other and do the same with the other optical tube. Here you get another perfectly comfortable image. Now open both eyes and remind yourself you are seeing two perfectly comfortable images, don't concentrate on the extent of the overlap or tell yourself 'it shouldn't look like that', just look at the subject. I find that focusing solely on the subject and ignoring the strangeness of the overlap means I have no discomfort and can enjoy the subject.

As for the close focusing mechanism leading to unreliability or other failure, I have yet to encounter such a thing, and I can assure you that Greenshanks and Great Northern Divers look just as beautiful through binos with a 1.0 metre close focus as through ones with 3.0 metre close focus. They are the right shape, the markings are as they should be, the only difference being that I can use the 1.0 metre focusing binos to observe inter-tidal marine life in rock pools and enjoy another dimension to our days out on a Scottish coast. I am over retirement age and have been enjoying close focusing binos for many years and have yet to encounter any problems caused by this facility.

One reason why both me and Troubadoris value a close focus is that it is not infrequent that we find ourselves unexpectedly close to a subject as we come around a boulder or a bush or some other kind of cover. In Scotland it might be a Field Vole or Gold-ringed Dragonfly, in France it might be a water snake swallowing a fish or a huge green lizard (all real-life examples) and the last thing we want to do is to scare the creature off by both of us having to step back a couple of steps in order to focus our binos on the subject.

When close focusing is so useful for observing so many divergent forms of life I find it hard to understand how this can qualify as a 'niche interest'. To me a 'niche' suggests a very limited number of interests, perhaps only one.

Lee

Click to expand...

Excellent advice and points.

--AP

Rico70 said:

...we see that a 10x binocular that focuses at 2.5m (8.2ft), has the power to virtually bring the user up to 25cm (10") away. Mathematics is simple. Therefore, 8x binoculars should focus at 2m (6.6ft) and 7x at 1.75m (5.7ft), etc.
This virtual focus distance (25cm - 10") is already "manna from heaven" for any presbyopite and also for others. But it is also very beautiful and much better to be approached virtually at 20cm (8 ") distance, to see the same objects with greater magnification and detail...

Click to expand...

This is a brilliantly inciteful way to think about the close focus performance of bins.

--AP

pete_gamby said:

...So there is some correlation to price but also to close focus distance - that was a surprise to me to be honest...

Click to expand...

Maybe it just shows that folks who buy bins without close focus don't focus their bins much, as Lee noted, or, I think likely, that they are less attentive to focusing errors (which are more obvious at close distances). I can't tell you how many cheap bins I've tried that have severe lack of synchronous focus in left and right barrels but that garnered no complaints from their owner.

--AP

Rico70 said:

...Do you remember if it works well and if it can really resolve the issue?

Click to expand...

In my experience, variable-ratio works perfectly. Unfortunately, it has only been implemented in a few bins that I'm aware of, namely some past Brunton Epoch models, past Minox HG models, and the Pentax Papilio. I'm not sure that the Papilio is continuously variable ratio, but it certainly adjusts focus more quickly at close than far distances.

I look forward to the day when variable-ratio focus is the new normal. Such an obvious improvement to make, low-hanging fruit for implementation in a close-focus bin, which would be much more a game-changer in practical terms than the much trumpeted small improvements in lens materials or coatings that we're always getting.

--AP

Alexis Powell said:

This is a brilliantly inciteful way to think about the close focus performance of bins.

Click to expand...

Alexis, you have all my respect for noticing. And thanks for your comments. I'm glad to see interest in certain technical insights.

To add more examples, when the Pentax Papilio 8.5x focuses objects at a distance of 50cm (20"), it will be able to project the user at the virtual 6cm (2.4"), and let him in incredible experiences of 'microscopic' freehand observations.

The larger the magnification, the greater the viewing distance, compared to the apparent magnification of the object.
Thus, at the same viewing distance, greater magnification will provide greater 'microscopic' detail of the object.

Generally, binoculars with roof prisms will have the objectives on the same axis as the eyepieces. Therefore they will be suitable for providing good close-up images, up to virtual distances of about 15cm (6") or slightly less; which is already a very good approach, compared to the 50cm (20") of some models.
While, binoculars with normal (not inverted) Porro prisms, widening the parallax of the entrance pupils too much, are often quite inadequate for virtual distances of less than about 30cm (12").

But all this is a bit subjective and depends a lot on the various optical constructions used. And it is better to try each binocular in the field separately, in order to make personal evaluations and understand the suitability or otherwise of the various models.

Alexis Powell said:

In my experience, variable-ratio works perfectly. Unfortunately, it has only been implemented in a few bins...

Click to expand...

If it works well, without defects between left and right and without too delicate complications, it can be an excellent system to be adopted normally, even in my opinion.

I would love it even if they adopted the solution with fast central ring and the double dioptric adjustment on the eyepieces.
Maybe with a lockable limit switch on the central ring, to improve the IF use of the eyepieces.

The best of the two or even both, if working, would certainly be a real new step forward (at least for users). :t: