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Parallax vs Focus

 
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  #29  
Old 01-10-2006, 06:47 PM
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Join Date: May 2005
Location: England
Posts: 77
Re: Parallax vs Focus

Sorry to disagree Bart i have seen 10's of different models and also had the misfortune to end up with one some years back. 5 1/2" of movement at 100 yards when in focus dependant upon where head/eye was placed.
This has nothing to do with pa/focus adjustment, you still get it when there is a bad one, usually asian build.
Never seen a decent Leup standard or modded suffer from this parallax. As long as the ret can be seen, you could move your head around and the zero will not change whether focused or not.
If scope is focused at another range it will not be as clear as it should, more than likelt blured and or will not be visible at all. So if pa/focus for clarity at every range ignoring what scope says, it is deemed correct for that distance, hence rangefinding a good bloke will get the range within 3% every time.
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  #30  
Old 01-11-2006, 05:23 PM
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Join Date: Dec 2005
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Re: Parallax vs Focus

Jonny, I understand why you've disagreed with what I said. I too, have looked through a few scopes that had parallax when the target image was focused very sharply. Here's how it happened.

In every instance, the scope's eyepiece was not focused properly on the reticule but instead either in front of it or in back of it. When the scope's front lens was turned/moved to focus a sharp image for the user, that image was in the same plane as the eyepiece was focused at. And yes, the reticule appeared to move relative to the target when the eye was moved around behind the scope. This is a common occurance.

Now here's the rest of the story. When the scope's eyepiece was correctly focused on the reticule, then the scope's front/objective lens was refocused for the sharpest image, the reticule no longer moved on the target as the eye moved around behind the scope.

It is opto-physically impossible for a scope sight to have its reticule appear to move relative to the target when the eye's moved around looking through the eyepiece when the target image and eyepiece are both properly focused on the reticule.
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  #31  
Old 01-11-2006, 11:49 PM
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Join Date: Dec 2001
Location: Mukilteo, WA
Posts: 1,091
Re: Parallax vs Focus

I think I understand exactly what you're saying, Bart. When I first got my 4.5-14 LR, I did the old "look at the sky, look at a wall" focus for the eyepiece--just like the instructions say. I found at the range the first couple of times, when parallax was eliminated the crosshairs were blurry. When it was "focused" with the side wheel, it had parallax.

I came to the conclusion that the best way to focus the eyepiece was to first eliminate parallax while aiming at a target on the range. Then, focus the damn eyepiece until both the target and crosshairs are sharp. Does that sound like a good method to you?
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  #32  
Old 01-12-2006, 08:07 AM
 
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Re: Parallax vs Focus

O'kay, so I read all of this and it brings up one very important question for me since I just bought a Leupold VXIII 4.5-14x50 LR with the side "focus". Is it going to be a pain to get everything focused and shooting straight at coyotes inside of 400 yds? The vast majority of my shots are within 200 yards though. I just don't want to have to mess around with a bunch of focusing while I've got a coyote trying to get down-wind of me, and I also want to get good heart/lung shots. Will this be an issue for me? [img]/ubbthreads/images/graemlins/confused.gif[/img]

Thanks,

Rusty
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  #33  
Old 01-12-2006, 09:12 AM
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Join Date: Dec 2005
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Re: Parallax vs Focus

Jon A, you should first focus the eyepiece such that your aiming eye gets perfect instant focus on the reticule. Our eyes nature is to automatically and instantly focus on what we're looking at. After the eyepiece is set correctly for your aiming eye, then move on to focusing the scope's front lens at the target's range. This is the best/only way to set up the scope for ones aiming eye.

Here's how to do it correctly:

1. Unlock, then back out (unscrew) the scope's eyepiece to where the reticule appears fuzzy or out of focus when you look through the scope for only 1 second.

2. Screw the eyepiece in one turn, then with both eyes, look at something about 100 yards away. While looking at that 100-yard point, move the scope quickly to your aiming eye then look through it for only 1 second, then put the scope down. If the reticule appeared fuzzy, screw the eyepiece in one more turn, then repeat this step. If the reticule starts appearing sharper, go on to step 3.

3. Screw the eyepiece in one-half turn, then with both eyes, look at something about 100 yards away. While looking at that 100-yard point, move the scope to your aiming eye then look through it for only 1 second, then put the scope down. If the reticule still appeared a little fuzzy, screw the eyepiece in one more half-turn, then repeat this step. When the reticule appears very sharp the instant you look through the scope, go on to step 4.

4. Lock the eyepiece in place. Don't ever move it unless your eyesight changes (new perscription for your glasses, etc.).

5. Put the scope in or on something that holds it still while you look through it at a target exactly 100 yards away (yes, measure off the distance to do it). Set the scope's focus for 100 yards (if marked, otherwise use your best guess).

6. Look through the scope with the reticule on the target then move your eye around and look for relative movement between the reticule and target. If the reticule doesn't stay on the target, change the scope focus a small amount then retest. Repeat this step until moving your eye around looking through the stationary scope shows no relative movement between the target and reticule. Then go on to step 7.

7. Note where the 100-yard mark on the objective lens focus is relative to the index mark. Make a new index mark at the 100-yard line. This is your particular scope's new index mark. Cover up the old one with something. When you set the scope's infinity setting at this new index mark, the scope will be focused pretty close to infinity. And setting any other range mark to this new index should result in zero parallax at that range.
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  #34  
Old 01-12-2006, 09:15 AM
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Re: Parallax vs Focus

Rusty, focus your scope such that it's parallax-free or focused at about 150 yards. It'll be just fine for targets up to 400 yards.
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  #35  
Old 01-12-2006, 10:58 AM
 
Posts: n/a
Re: Parallax vs Focus

Thanks Bart....I was getting nervous. This board is priceless. I've learned more in just a few days of lurking than I have in years of actively posting on other boards.

Thanks, guys!

Take care and God Bless,

Rusty
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