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Bushnell 4200 2.5 x10 x 40 question

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Category: Scopes
Forum Name: Rifle Scopes
Forum Description: Centerfire long gun scopes
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Topic: Bushnell 4200 2.5 x10 x 40 question
Posted By: dimecovers3
Subject: Bushnell 4200 2.5 x10 x 40 question
Date Posted: December/29/2007 at 14:43
I just opened a Christmas gift of a 4200 2.5 x 10 x 40 scope.  I noticed that the crosshairs were razor sharp as it came.  I also noticed that looking off my deck into the woods that once I passed 6x things lost focus as far away as 100 yards.  If I slowly turned the power down they got real crisp and clear at about 6 x power.  Is this normal?  My 2.5 x 8 Leopold does not seem to change focus on close in objects at 8x
 
If this is normal it really limits the idea of making a very precise shot on a very small critter at what would likely be my average range predator hunting.



Replies:
Posted By: Focus
Date Posted: December/29/2007 at 15:31
I usually adjust the focus to my eyes on any new scope at 100yds. I do this with differing font of black print on a white background. You will find that when focussed in this manner to your eyes, the reticle will be in sharp focus when viewed at a balnk background like the sky. It should appear crisp and sharp and clear now to your eyes when viewed at longer distance or close. Try that and see how it works, they usually come focussed for about average vision.

Focus

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I Can See Clearly Now......<><

If Accurate rifles Are Interesting.....I've Got Some Savages That Are Getting Mighty Interesting......


Posted By: dimecovers3
Date Posted: December/29/2007 at 15:40
The reticle is sharp all the way up to 10 power---it's the thing I'm looking at that is less than focused.  I just looked at a truck about 100-120 yards down the street that has its front end off.  I could clearly see the fins in the radiator at 6x but as I moved up to 10x they got harder to define.
 
Are you saying focusing the eyepiece changes this?  The owners manual does not mention this.  It only talks about the reticle being preset at the factory for 20-20 eyes (corrected or without correction)  and how to adjust it to make it look sharp if it is not. It does not sayanything about focusing the scope to your eye to see objects.


Posted By: Focus
Date Posted: December/29/2007 at 16:17
I realize this, but there is quite a bit of leeway in focusing where the reticle is quite crisp. Yes, turning the ocular focus will focus the scope to your eyes, if you had tried what I had suggested you would know that already. The faster euro style eye pieces just do it faster than the slower lock ring style. You can set the ocular focus where your eyes see best and still have the reticle in crisp focus. I use 100yds....the same place parallax is adjusted out at, on a non-AO scope. If the diopter didn't focus for a particular eye focus why is it set for 20/20 at the factory? I have a buddy with crazy vision, wears thick glasses and when he has adjusted the ocular to be correct for his eyes I can barely see the target to shoot with his gun, I can't see bullet holes at all. Of course if I started to adjust the ocular to focus for my eyes, I would mess it up for him. How do you figure shooters use an acuity chart to test resolution if the scope isn't focused to their eyes? The lines would all be blurry and impossible to actually evaluate. Correctly focusing your scope to your eye will make it razor sharp and as clear as the lens grinding and quality allow for in a given scope brand. The last 4200 I adjusted the reticle stayed sharp and crisp through 3 1/2 complete revolutions while the actual focus on some small font print at 100yds went from blurry to crystal clear and back to blurry again in the same amount of adjustment. Set your scope on 10x and focus the diopter on some different sized font at 100yds, than raise the gun to the sky and see if your reticle isn't still sharp. I'm simply telling you how to fine tune the focus to your eye.


If your scope still blurs as you adjust the power ring, your scope is defective....send it back.

Focus

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I Can See Clearly Now......<><

If Accurate rifles Are Interesting.....I've Got Some Savages That Are Getting Mighty Interesting......


Posted By: dimecovers3
Date Posted: December/29/2007 at 17:56
Thanks!  I will try it as you suggest.  I'm really surprised the owners manual would not mention such a basic thing.  I have focused reticles before , but have never noted a scope that was out of focus to my eye throughout the power range.  On the other hand I have never had a 4 power zoom or a scope over 8 power.
 
I have not bought a scope in the last two years which is about the time my eyes went south fast and I had to get my first pair of glasses.
 
Are you aware of anything available that I could download and print to use for a focus test?


Posted By: Focus
Date Posted: December/29/2007 at 18:06
Well I just hope its simply a matter of the scope diopter focus being off. It could still be something wrong if it doesn't correct it. Go down to the great scope off of 08 and copy the acuity chart I posted in there. It will work fine, just focus till you can read the smallest line of print possible on max power. Good Luck and let us know what happens afterwards.....

    Focus

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I Can See Clearly Now......<><

If Accurate rifles Are Interesting.....I've Got Some Savages That Are Getting Mighty Interesting......


Posted By: dimecovers3
Date Posted: December/29/2007 at 19:20
I hope that is all it is.  I guess I'm a little puzzled why 6x looks so good, but not 10x
 
Anyway I found this site with a downloadable .pdf  of the USAF test pattern and will print one on the laser at work. http://www.takinami.com/yoshihiko/photo/lens_test/pdml-procedure.html - http://www.takinami.com/yoshihiko/photo/lens_test/pdml-procedure.html
 
 
While looking for a suitable chart I came across a thread that has been going on for seven years on optical qualities and test targets on a birding forum.  Man!!! Do those people take their optics serious.


Posted By: Focus
Date Posted: December/29/2007 at 20:05
That test acuity chart will work great. Yes birders actually take optics a lot more serious than most shooters. They are real interested in color correction and rendition too.

Focus

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I Can See Clearly Now......<><

If Accurate rifles Are Interesting.....I've Got Some Savages That Are Getting Mighty Interesting......


Posted By: dimecovers3
Date Posted: December/29/2007 at 20:46
this page is where I found the chart..just passing it on in case there are some good tidbits you might find of interest
 
http://www.normankoren.com/Tutorials/MTF5.html - http://www.normankoren.com/Tutorials/MTF5.html


Posted By: dimecovers3
Date Posted: December/31/2007 at 17:45
Focus,
 
I tried your suggestion with my scope today.  Did not really seem to change anything drastically.  I can turn the end of the scope many revolutions and not see any apparent change in the reticle sharpness. 
 
I tried looking away several times as the booklet said to, but I can't see where it made much difference. It did seem to sharpen some slightly from 120 to 60 yards, but 40 to 60 yards on 10x was still not sharp till I went down to 6x.
 
Might be my eyes have a prescription for bifocals and the adjustment only deals with near sightedness and far sightedness depending on which way you turn it. My Leupold makes my eyes young again so I'm not sure it is me.  Maybe I got a bum scope or maybe it is just not possible for a scope to focus from almost zero to infinity.  Wish I had more experience with higher power scopes and what to expect.
 
The eye relief is more critical than what I am accustomed to as well.
 
Do you have any pointers for getting the reticle focused without having your eye compensate and decieve you?


Posted By: dimecovers3
Date Posted: December/31/2007 at 17:49

P.S. How do enable the edit funtion for my posts?



Posted By: cheaptrick
Date Posted: December/31/2007 at 18:02
Originally posted by dimecovers3 dimecovers3 wrote:

P.S. How do enable the edit funtion for my posts?

 
Click on "Post Options" and a drop down box will reveal "Edit post", click it.


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If at first you don't secede...try..try again.


Posted By: dimecovers3
Date Posted: December/31/2007 at 18:28
I only get "quote" when I do that...strange.


Posted By: Focus
Date Posted: January/01/2008 at 07:02
The eye relief will be closer than the leupold, I would send the scope back and see if they can check it out. My 4200 is stunning for resolution (crisp clear acuity) and I suspect that it can be fixed. Heres an idea, see if you can find one to look thru at a sporting goods or gunshop, see if another model 4200 does the same thing. This would let you see if it is your eyes or the scope, I suspect it is the scope....

Focus

-------------
I Can See Clearly Now......<><

If Accurate rifles Are Interesting.....I've Got Some Savages That Are Getting Mighty Interesting......



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