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Bushnell permafocus -- anyone tried them?

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#1 Protheus

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Posted 02 February 2008 - 03:19 PM

I've been wondering about these things, recently. See here, for example. Has anyone tried them, and are they reasonable? What I'm really wondering is whether such a thing can be done without compromising the optical quality of the instrument. In my case, any binoculars I have are used exclusively for astronomy (which means I don't adjust the focus much, anyway...), so feel free to take that into account.

Chris

#2 EdZ

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Posted 02 February 2008 - 03:48 PM

Do Not buy perma-focus binoculars.
When you find that it is not precisely focused for the objects you want to view, you have no options.

edz
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#3 Roadbike

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Posted 02 February 2008 - 05:19 PM

I've been wondering about these things, recently. See here, for example. Has anyone tried them, and are they reasonable? What I'm really wondering is whether such a thing can be done without compromising the optical quality of the instrument. In my case, any binoculars I have are used exclusively for astronomy (which means I don't adjust the focus much, anyway...), so feel free to take that into account.

Chris

If you are not concerned about having images sharply focused and your eyes both focus the same place then those glasses can work. I've tried a pair and found to deliver frustratingly poor images. But I expect pinpoint stars, visible details on bird feathers, etc.

Permafocus glasses are also known as never-focus for good reason.

#4 Protheus

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Posted 02 February 2008 - 06:31 PM

Something like the answers I expected. To be clear, I'm not in the market for binoculars of any sort at the moment; It's more for my own curiosity than anything...

Chris

#5 snorkler

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Posted 02 February 2008 - 11:51 PM

People's eyes focus differently, even at infinity. During my astronomy volunteer time in the national parks, I find people frequently change their focus from mine, or from the previous observer's focus. One focus does not fit all - either in scopes, or in binoculars.

#6 DJB

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Posted 03 February 2008 - 10:40 AM

And one more thing.

I presume the philosophy behind these things is that all young people have perfect 20/20 or better, to which these are directed?. Not true. Somehow these are supposed to be pre-focused at infinity, which just won't fit everyone, as has been discussed above.

My advice: Stay away and just laugh it off.

Best regards,
Dave.

#7 Intergallactic

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Posted 21 August 2012 - 06:42 AM

Exactly how do the optics work? I took some of them apart and they looked like normal binos. Is the wide dof due to a particular type of eye piece design?

#8 Rich V.

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Posted 21 August 2012 - 09:39 AM

They should look like normal binocular but without a focusing mechanism. I believe these "focus free" binos are set to operate at their hyperfocal distance.

http://en.wikipedia....rfocal_distance

Unfortunately, because of deviation of our eyes from "perfect" vision, focus free may not work well at all for many users. As we age, our eye's ability to accomodate focus decreases and the range of clear focus through a fixed focus binocular will diminish as well.

"Focus free" is a poor compromise to make for a binocular or any optic that is expected to provide critical focus across a range of distances. :p I wouldn't recommend them to anyone.

Rich

#9 Henry Link

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Posted 21 August 2012 - 11:08 AM

Exactly how do the optics work? I took some of them apart and they looked like normal binos. Is the wide dof due to a particular type of eye piece design?


They are normal binoculars. There is no unusually wide dof in these things. All binoculars of the same magnification have essentially the same dof. Neither more nor less dof can be designed into the optics.

Large field curvature would make a non-focusing binocular a bit more useful by allowing the eye to focus on closer objects toward the edge of the field, but that shouldn't be confused with true dof.

Also, reducing the binocular aperture enough to make the exit pupil smaller than the entrance pupil of the eye really does increase the dof, but in that case it's the dof of the eye that increases, not the binocular.

#10 BillC

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Posted 21 August 2012 - 11:17 AM

As that great American Sage once said—or said 100 times, I can’t remember—“Good advertising doesn’t have to be meaningful or accurate; it just has to be believed.”

Some time back Steiner (then being imported by Pioneer Research) had an ad that said:

“SPARC coatings reflect electromagnetic waves back into the light beam.”

Now, I’m sure that bit of knowledge gave some people the prideful shivers. But, what did it really mean?

SPARC = Simulated Penetration Anti-Reflective Coatings

“Simulated Penetration” is a concept from a warped Psych lesson I had as a freshman in college and has absolutely NOTHING to do with optics!!!

Next, light IS electromagnet waves, so how can it reflect back into itself? Still, it sounds mighty impressive to those for whom thinking is not a strong suit.

Ricky gets bent outta shape when I address things like this the way a want to but, have pity on me . . . I can’t help it!

For some people, a binocular that doesn’t require focusing is a development of the computer age. Really, it is a way to sell a production shortcut as a FEATURE! I’ve stood behind the counter at Captain’s (Cory can verify) and been told (more than once) by a “real man” type that his “Perma Focus” was just as good as anything I had in the bino case: Swarovski, Zeiss, Leica, Nikon, Kowa, Fujinon, etc.! How can you help in such situations? None are so blind as those who REFUSE to see and the desire to justify a less than stellar purchase and be overwhelming!

The secret: For those who are young enough, the ciliary muscles around the eye will force the issue and bring the PERSON not the BINOCULAR into focus! Stand by for a headache. Probably the saddest thing about this is that most who fall into this trap are older people who are beyond what those ciliary muscles could once do for them.

Curmudgeon out.

BillC


#11 StarStuff1

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Posted 21 August 2012 - 11:48 AM

Several years ago I picked up a 10x50 Simmons fixed focus bino at a swap table. No case, lens caps or strap but only $5. I was thinking of making a couple finder scopes out of the optics. After thorough cleaning the thing gave a decent image that was almost in focus at infinity...for me. Terrestrial viewing was blurry.

I left them intact as an example for others as what NOT to buy.

But hey, only $5 :crazy:

#12 Tony Flanders

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Posted 21 August 2012 - 01:19 PM

Some time back Steiner (then being imported by Pioneer Research) had an ad that said:

“SPARC coatings reflect electromagnetic waves back into the light beam.”

What did it really mean?


Oh, it's clear enough what it means, all right.

Light being an electromagnetic wave, it means that the anti-reflective coatings are failing to do their job.

Of course, no coating can prevent all reflection, so nobody can possibly complain that this is false advertising. The coatings are indeed reflecting light back the way it came, just as this says. But still, it doesn't seem like something one would want to boast about ...

#13 Simon S

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Posted 21 August 2012 - 03:23 PM

I have to agree. Buy a focusable binocular, these all fixed focus binoculars are restricting.

#14 KennyJ

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Posted 21 August 2012 - 03:28 PM

I'd always thought this item was a special mirror for use in elderly ladies' hair salons.

Kenny

#15 Intergallactic

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Posted 23 August 2012 - 05:01 AM

LOL. Right, so I carefully focused my trusty pair of 12-42 to infinity. Guess what, I have a permafocus set as long as no one else disturbs the focus adjustment!!

I had never noticed that about binos before. I wonder if I ever would have figured that out on my own. LOL

#16 Jon Isaacs

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Posted 23 August 2012 - 05:42 AM

LOL. Right, so I carefully focused my trusty pair of 12-42 to infinity. Guess what, I have a permafocus set as long as no one else disturbs the focus adjustment!!

I had never noticed that about binos before. I wonder if I ever would have figured that out on my own. LOL


Just don't go birding with them...

Jon






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