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Parallax vs Focus

 
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  #22  
Old 10-22-2005, 07:03 PM
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Join Date: May 2005
Location: England
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Re: Parallax is not calibrating???

By doing what you have done- moving the small wheel, you have not really altered anything at all. Who cares if the 400 is in the middle or at the end of the adjustment.

Now on the other hand, i think this is what you are after. If you only intend to see and shoot at 400 yards i would suggest put the side wheel back as was and alter the front lens assy, quite easy just need to screw it out to reduce the max range which will reduce the short range as well. The gaps at the high end will be wider apart.
Effectively, once adjusted to liking the 400yd could come in at the end of the rotation of the wheel and you will need to mark your own as all other markings will be miles out. Just check it is not camy, possibly the last 5 degrees!
Try half a turn for starters.
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  #23  
Old 10-31-2005, 01:32 PM
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Re: Parallax vs Focus

[ QUOTE ]
In a fixed power scope, or in a variable with a "First image plane reticle", the reticle would be placed in this image plane.<P>This is where Premier Reticle puts those magical "Gen II" reticles.

[/ QUOTE ]
Here's a silly question: What effect does placing the reticle on the first focal plane for a given scope have on parallax? Make it better, worse, no change, etc?
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  #24  
Old 01-05-2006, 09:46 AM
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Re: Parallax vs Focus

This thread is one of the most interesting I've read; anywhere in the shooting sports. I'm convinced that few readers know or understand what's happened over the years.

In the beginning, when someone invented a scope sight that could be set for a good image of both reticule and target, that setting process was called focusing. It works exactly the same way as a single-lens reflex camera. The lens at the front moves such as it focuses the subject/target on a plane where the reticule/ground-glass is. Some of these optical devices have another moveable lens that can focus the user's eye on the reticule/ground-glass for visual clarity. The objective lens adjustment was/is usually calibrated in range.

Back then, parallax was the effect seen by the user when their eye was moving off center from the optical axis; the reticule/ground-glass appeared to move relative to the target/subject. It was called parallax. It was never considered to be adjustable in a scope sight except by moving the user's eye back to the optical axis.

Something in the rifle scope industry changed not too long ago. I've no idea where the idea that moving a rifle scope's front (objective) lens would "adjust parallax" first originated. But the person who started it (along with those who perpetuate it), in my opinion, are doing a diservice to the shooting sports.

Since the phrase/term "parallax adjustment" has came about, the number of questions about it has increased dramatically (percentage of scope owners asking about it, not just more because there's more of 'em).

Nothing's changed except the terminology. I sometimes wonder if the adjustments on binoculars used to get a sharp image will soon be called the parallax adjustment; they do the same thing as a camera or rifle scope. And the spotting scopes used to view distant objects, will their image-sharpening adjustment (which also does exactly the same thing) soon be called the parallax adjustment? God help us if folks start calling prescription eye glasses parallax adjusters.
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  #25  
Old 01-06-2006, 06:49 PM
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Re: Parallax vs Focus

Absolutely correct Bart, extremely confusing, i think it is the Asian manufacturers to my knowledge at least prior to 1991. Leupold put FOCUS on the little sidewheel on the original Mark 4, Vari X 3 and VX3, virtually the same to use as a camera.
Also confirm i have seen nothing that will alter the proper term- parallax by the user. If ret appears move, tuff get rid of the scope.
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  #26  
Old 01-07-2006, 09:14 AM
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Re: Parallax vs Focus

Jon A, putting the reticule in the first image plane (primary focus of the objective/front lens) does nothing for parallax. There'll always be instances when the reticule and target image aren't on the same plane.

And doing this will also let the reticule increase in size (thickness) as magnification is increased 'cause the two sets of lenses in the erector tube moving front to back is what changes magnification.

Reticules in the first image plane also appear to move off center as elevation and windage adjustments are made. This happens 'cause the back of the erector tube is fixed and the front points to a different place in that first image. The only way to fix this is to anchor the erector tube's front end at the first image plane then move the adjustment turret back closer to the eyepiece. Which wouldn't be a bad idea 'cause the adjustments would be easier to reach.
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  #27  
Old 01-08-2006, 08:13 AM
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Re: Parallax vs Focus

Jonny, your comment"

"If ret appears move, tuff get rid of the scope."

...doesn't make sense. This will happen with every scope sight on this planet whenever the scope's focused at a different range than the target is at AND the shooter's eye is off the scope's optical axis.
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  #28  
Old 01-10-2006, 05:54 PM
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Re: Parallax vs Focus

Thanks for the info, Bart.
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