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Bushnell Insta Focus

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#1 Mxplx2

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Posted 20 January 2013 - 02:21 PM

I bought 10x50 Bushnell binos with insta focus as a step up from my 7x25's. As a newb, I wasn't thinking quality. I just wanted bigger and I wanted it now, and they were cheap. I found while using however, that focus had to be re-adjusted shortly after being set. It would be set only to have to re-set. I lived with it for a while, but this morning I thought I'd give it a closer look. It seems that you can change focus by just pushing in on the eyepieces as you hold the binos against your eye sockets. Pushing in by hand you can see the insta focus lever move as the eyepices move in. I can't see any kind of fix for this except maybe finding the best focus point while getting a star to a pinpoint, and locking the adjustment in place somehow permanently. I don't believe that focus need be re-adjusted from object to object, since it's all on the same dome so to speak. If I'm wrong, then I would like to know. Otherwise, they work pretty well for the buck.

#2 Mark9473

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Posted 20 January 2013 - 02:32 PM

Seems you got what you paid for, unfortunately. I hope somebody will drop by with a fix.

#3 BillC

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Posted 20 January 2013 - 10:03 PM

Hi Mxplx2:

The following is from a monograph of mine called De-MYTH-Tifying Binoculars, and has been around for at least the 9 years I've been here. But, while some would dismiss MY comments, you've experienced it for yourself. Thus, it is now part of YOUR knowledge, too.

"If you own one of these units now, you may prove this to your own satisfaction. Set the eyepieces all the way out with the lever. Then, place the lower axle on the end of your second or third finger, with your thumb on the extended upper end. Now, squeeze gently. See how easily the mechanism moves? After focusing the left eye, this weakness in the design can cause it to de-focus with just the pressure of holding it against your face, while trying to focus the right eye. The result? A binocular of dubious quality just got worse, as you must refocus incessantly in hopes of maintaining a reasonable image."

Cheers, :jump:

BillC

#4 SMark

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Posted 20 January 2013 - 10:33 PM

It's easy to say that this is just one of those things that distinguishes the lower quality binoculars from the higher quality binoculars. But I have noticed in a number of cases where similar binoculars with similar designs and features and similar prices can be compared, and one will have a super slippery center focus and the other will have a rock solid center focus. It certainly can't be all that difficult to get this right.

Is the problem in the design, the manufacturing, or the adjustment? :question:

#5 BillC

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Posted 20 January 2013 - 10:43 PM

"It certainly can't be all that difficult to get this right."

But, you have to care. And, as long as people are willing to put their money down, there's no reason to care.

BillC

#6 SMark

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Posted 20 January 2013 - 11:50 PM

Well... even assuming that they don't care... Wouldn't this cause enough returns such that it would be easier for them to just "get it right" the first time?

#7 BillC

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Posted 20 January 2013 - 11:59 PM

Well... even assuming that they don't care... Wouldn't this cause enough returns such that it would be easier for them to just "get it right" the first time?


One would like to think so. But then, look at some of the others that have been discussed here that are optically or machanically inferior [see guys; I didn't say "junk."], that continue to sell. Aunt Myrtle doesn't know or care, and there are a lot of Aunt Myrtles out there who just think optics are magic and come from another world. Perhaps, you think I'm harse. But, if you worked in optics retail for a couple of decades, you would switch from thinking "He's harsh," to "He's harsh, but accurate." :(

Cheers,

BillC

#8 SMark

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Posted 21 January 2013 - 12:46 AM

Perhaps, you think I'm harse.


Naw... Not even close to it. I've always found you pretty much spot-on. But I would like your opinion about whether this particular issue with the center focus mechanism is a problem in the design, the manufacturing, or just improper adjustment?

#9 BillC

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Posted 21 January 2013 - 02:01 AM

Design AND Manufacture.

Adjustments = add more grease or tighten tolerances! Other than that, you’re usually left to prayer. :praying:

Of course, you can spend more money and stop worrying.

As Manufactured for inexpensive instruments, the Design is inherently flawed. In addition, it should be realized that SOME people in SOME product lines do not pride themselves in their contributions to the world of optics; they pride themselves on how many boxes they can get out the door . . . this month. And, was it more than last month? :money:

They will sell us whatever we’re silly enough to buy. And as long as we have people running around bragging about the “great” bino they bought for less than $50, it will continue to be that way. Make no mistake, Japan AND China can match the quality of instruments from Europe. However, they will require a greater price. And, some folks find it easier to complain about what they can’t afford than to plan a circuit to see, bargain basements, thrift stores and pawn shops where instruments can be purchased for pennies on the dollar. :woohoo:

I grew up thinking “poverty” was for rich folks. And, being out of work for 2 years, I’m there again. BUT, if I wanted a specific new binocular, I’d find a way to get it in short order, just like so many who complain COULD DO. :scratchhead:

We all choose what we consider important and what we’re willing to spend money on. Many times people have told me they couldn’t afford this or that $200 bino, only to walk to the parking lot and saddle up their Beemer or Lexus. I’m shedding no tears for them. :mad:

Today, I’m seeing a lot of center-focus binos advertised as “waterproof.” Do you think the average consumer knows how a center-focus bino gets to be that way or how long in inclement weather it will stay that way?

All they know is what the salesman told them or what they’ve read. But that’s okay; the collimation is usually shot before the bellows gets a hole in it.

Cheers, :jump:

BillC

PS We lost to the Left Coast , today! :shrug:

#10 Jon Isaacs

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Posted 21 January 2013 - 07:53 AM

. I don't believe that focus need be re-adjusted from object to object, since it's all on the same dome so to speak. If I'm wrong, then I would like to know. Otherwise, they work pretty well for the buck.



I have owned similar binoculars and it is very frustrating, just the pressure against your face causes them to focus. I know of no simple adjustment or repair, I imagine one could jury rig something, a piece of tape on the focusing shaft, even a bit of super glue..

Jon

#11 Simon S

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Posted 21 January 2013 - 01:06 PM

The problem with this focus system is that it has a shallow slope cut into the focus paddle in which a pin sits. Any application of pressure will result in focus shift.
Fold down the eye cups and do not contact the oculars when viewing, or hold the paddle when viewing.

#12 Mxplx2

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Posted 21 January 2013 - 04:09 PM

The problem with this focus system is that it has a shallow slope cut into the focus paddle in which a pin sits. Any application of pressure will result in focus shift.


That was my supposition that it is a design problem, i.e. almost like a 1 to 1 gearing in both directions. Thanks for all the replies.

#13 Simon S

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Posted 21 January 2013 - 04:55 PM

Oh and like the Cumulonimbus avatar!

#14 BillC

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Posted 21 January 2013 - 08:08 PM

Silly Simon; that's not a "Cumulonimbus." It's a cloud. 'Kinda shaped like a Daurian Jackdaw about to take flight. 'Never saw a white one, though!

BillC

#15 ronharper

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Posted 21 January 2013 - 08:56 PM

Mxplx2,
You are right about the design problem. It's like parking a car in high gear--the engine will not be forced to turn over many times per wheel spin, so it will tend to roll off.

I would fix a block of just the right thickness under the paddle arm. Maybe make a wedge, slide it underneath until the adjustment is right, and glue it down right there.

I had (still have I will admit) an old 7x35 of these. For birding it was at least very fast to focus, which is the claim of the name. I thought it was well worth the little money it cost, but I can see that for astro use it's a bad choice.
Ron

#16 Mxplx2

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Posted 22 January 2013 - 07:51 PM

Oh and like the Cumulonimbus avatar!


That cloud was the only one around at that time, and it may have been from the cooling tower of the nuclear power plant many, many miles to the south, which just got whisked around into that shape by light winds. Not really sure.






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