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Is close focusing ability in a binocular REALLY necessary

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Old Tuesday 17th December 2019, 07:06   #1
42za
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Is close focusing ability in a binocular REALLY necessary

Hello All,

I cannot really understand why some people insist that a binocular focus below a certain distance.
If a binocular has a minimum focus distance of say 8 or so meters this should be ok , after all binoculars were originally designed to observe distant objects.

If one must look at nearby objects , play at being Sherlock Holmes and use a hand magnifier.



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Old Tuesday 17th December 2019, 07:20   #2
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Being able to focus to 3m or so enables you to look at butterflies and other small stuff that’s not far off. Though being able to get too close risks them getting spooked and flying off. I have an old pair of bins that can’t focus on the bird feeder on my back fence (?4-5m off) and it’s annoying, but that’s the only time I’ve had a near focus issue.
If I want to go on a mini beast safari then nothing beats the Papilios.

Peter
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Old Tuesday 17th December 2019, 07:53   #3
Troubador
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If you are an extreme specialist and only look at, for example, birds, then a close focus distance of 1.5 metres or so is probably not necessary for you.
If you are interested in all aspects of nature then close focusing binoculars open up many wonderful worlds including dragonflies, butterflies, moths, reptiles, life in pools and rivers, life in sea-side rock pools, not to mention flowers and lichens and fungi.
Have you ever watched a nature show on the television or on-line? Did you ever see a fantastic close-up of a butterfly on a flower and say to yourself: you never get views like that in real life? Because if you did, you are mistaken. Views like that are easily obtainable through close focusing binoculars.

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Old Tuesday 17th December 2019, 08:29   #4
Mark9473
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I find close focus mighty handy to read the water meter which is 30 cm below my garage floor.
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Old Tuesday 17th December 2019, 10:38   #5
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I find close focus mighty handy to read the water meter which is 30 cm below my garage floor.

then there are flowers and bugs to see on birding trips

edj
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Old Tuesday 17th December 2019, 11:16   #6
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Hello 42za,

I agree with you. 3m is fine with me.

Happy bird watching,
Arthur Pinewood
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Old Tuesday 17th December 2019, 11:42   #7
Rico70
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I find close focus mighty handy to read the water meter which is 30 cm below my garage floor.
Mark, for president !!!

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Old Tuesday 17th December 2019, 11:56   #8
Rico70
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Originally Posted by 42za View Post
If a binocular has a minimum focus distance of say 8 or so meters this should be ok, after all binoculars were originally designed to observe distant objects.
It also depends on the magnification. A 25x binocular that focuses 8m, is like an 8x focusing 2.5m or a 10x focusing 3.2m.
And of course it also depends on what you observe.
One day I was photographing ducks and behind me a squirrel was looking for food. I tried to photograph it, but the lens couldn't focus it. So I took the binoculars and I watched it easily with beautiful close-ups.
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Old Tuesday 17th December 2019, 18:16   #9
james holdsworth
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Another '' I don't need it / want it, why should you?'' thread...
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Old Tuesday 17th December 2019, 19:01   #10
Canip
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Hello 42za,

I agree with you. 3m is fine with me.

Happy bird watching,
Arthur Pinewood
Plus 1.

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Old Tuesday 17th December 2019, 19:52   #11
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Another '' I don't need it / want it, why should you?'' thread...
I think it's perfectly legitimate to question what is essentially marketing-driven inflation of specification numbers. It may be a niche requirement for some but a close focus of 1 m in a roof-prism binocular would preclude merging the images, even at reduced IPD.

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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Old Tuesday 17th December 2019, 20:05   #12
james holdsworth
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I think it's perfectly legitimate to question what is essentially marketing-driven inflation of specification numbers. It may be a niche requirement for some but a close focus of 1 m in a roof-prism binocular would preclude merging the images, even at reduced IPD.

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
That's not at all how the OP framed the question though....and a CF of 8m would be of little use to most birdwatchers, let alone those of us that like to observe insects etc.

The ''why we have CF bins'' has been done to death here and the questions asked have been answered dozens of times. The OP's premise is flawed off the trot - that bins are for looking at distant objects - not always true - we often want medium close objects brought much closer.
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Old Tuesday 17th December 2019, 20:19   #13
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For me, yes it's a necessity.

I once went to Norfolk in the hope of seeing, among other species, my first Yellow-browed Warbler. Someone pointed to a thicket and said "There's at least one in there". I carefully edged my way in, and in front of me was a warbler. The bins I had at that time focused no closer than about 5 or 6 metres, and the bird was only 3 or 4 metres away. I saw the features just about well enough for a positive ID, but thoroughly blurred. Yes, got a tick, but there was little pleasure in the sighting, and I made my mind up to get ones that focused much closer at the next upgrade.

Also, it's a joy watching dragonflies in superb detail from very close quarters.
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Old Tuesday 17th December 2019, 21:38   #14
Rico70
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The OP's premise is flawed off the trot - that bins are for looking at distant objects
I would say that it is understandable, since it is paradoxical that binoculars made to zoom in and to bring distant objects closer, is used to see objects at 2 or 3m.

However, I am certain that once some micro-observation experiences have been made, the OP might think again and accept this function as sought after.
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Old Wednesday 18th December 2019, 07:15   #15
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Originally Posted by Tringa45 View Post

I think it's perfectly legitimate to question what is essentially marketing-driven inflation of specification numbers. It may be a niche requirement for some

John
Since this is called Birdforum and is visited by birders it is understandable that the impression can be gained that binoculars are only used to look at birds, which are frequently distant objects.

However a few minutes viewing any nature show on the tv will reveal there is more to nature than only birds and many of these fascinating subjects are amenable to being studied using close-focusing binoculars.

As I posted earlier: if you are a specialist in bird observation you may not need a close focus, but if you are interested in a wide variety of nature observation subjects you will find a close-focus extremely rewarding.

In terms of the breadth and depth of the world of nature, an interest only in birds is a very narrow niche. By providing close-focus capabilities, binocular manufacturers are clearly hoping to attract buyers from the world of nature-observers as well as birders, and also providing a capability for birders who dare to 'spread their wings' and take an interest in other subjects, instead of remaining confined to the niche-world of birds-only.


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Old Wednesday 18th December 2019, 18:56   #16
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However a few minutes viewing any nature show on the tv will reveal there is more to nature than only birds and many of these fascinating subjects are amenable to being studied using close-focusing binoculars.
However, what is often overlooked is that there is a price to pay for the close-focusing ability: The focuser needs more travel and gets quite a lot more complicated and thus more prone to failure - remember the problems quite a few close-focusing binoculars had a few years ago? Also these binoculars typically require more complex optics, with a focusing lens between the objective and the prisms.

The situation is similar to having eyepieces on virtually all quality binoculars that can can be used by eyeglass wearers. There is also a price to pay, like a smaller field of view, larger and heavier and more complex eyepieces and so on.

I wish there were some simple, wideangle binoculars without a close-focusing ability, and not only binoculars that try to do it all.

Hermann

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. I need binoculars, if I need a field microscope I use one.

Last edited by Hermann : Wednesday 18th December 2019 at 19:07.
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Old Wednesday 18th December 2019, 19:19   #17
Rico70
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I wish there were some simple, wideangle binoculars without a close-focusing ability...
do you mean to have binoculars with fixed focus at infinity?

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Old Wednesday 18th December 2019, 21:03   #18
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Hermann (post #16)
Good post - I fully agree with everything.
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Old Wednesday 18th December 2019, 21:11   #19
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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
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Old Wednesday 18th December 2019, 22:18   #20
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If one wants some really close action, just get a Pentax Papilio 6.5X21 would be a suggestion.

Andy W.
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Old Wednesday 18th December 2019, 22:51   #21
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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
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

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Old Wednesday 18th December 2019, 23:26   #22
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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
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Old Thursday 19th December 2019, 01:12   #23
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Originally Posted by Tringa45 View Post
...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
Hello John,

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

Happy bird watching,
Arthur
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Old Thursday 19th December 2019, 08:12   #24
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Originally Posted by Tringa45 View Post
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
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.

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Old Thursday 19th December 2019, 16:00   #25
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... 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.
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:
Quote:
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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.
... 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.

Last edited by Rico70 : Thursday 19th December 2019 at 19:04.
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