Parallax

Wogpotter, your definition of parallax is the distance between two images on a single plane in an optical axis. I've never heard of that.

My definition is the popular one; the displacement or difference in the apparent position of an object relative to another viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. This is the one I used teaching meter reading when the needle's an eighth of an inch or so above the scales. Or when teaching optical sterescopic rangefinder operation for long range gunfire.

These are two different things. With mine, if the angle's zero, there is no parallax. With yours, there's always parallax because the images are separated by some distance on the optical axis even though the angular difference is zero.

So, unless we use the same system of measurement and/or definition, we'll have two different perspectives.
 
Pogybait said:
When you explain this, do it the Army way and use the KISS principle...
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Well, we've really stepped away from that principal. The Leupold reference keeps it simple, although it doesn't answer all your questions.

Pogybait said:
Is parallax only a problem with scopes greater than 9X...
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It's there with scopes less than 9x, but as with the Leopold example, it's not really significant for most intents and purposes. For most hunting purposes, I would argue that it's not generally significant even on more powerful scopes unless your form really stinks.

Pogybait said:
...and is this the reason most of the scopes hunters and others buy, are not greater than 9X?
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I think the reasons most hunters buy scopes less than 9x are the price point and need. Most game at standard distances can be taken with a magnification lower than 9x. Also, generally speaking, there is a significant price jump between scopes with 3-9x and scopes with more magnification.

Pogybait said:
Can a variable 9X scope be reduced in power and eliminate parallax?
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Parallax deviation is reduced with lower magnification. It is not eliminated.

Pogybait said:
I'm sure the price and quality of the scope has an effect on this.
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Not really. The most significant factors are magnification and objective size.

I'm a visual kind of guy. That's why sometime back I created the Excel workbook. It's kludgy, but it gave me a visual reference. Using it I learned some. But most importantly I learned that with decent form I can hunt most game at most distances without any concern for parallax deviation. For punching paper and really trying to improve my skills then I pay attention to parallax. For small game at long distances I pay attention to parallax. But even then I can keep it simple. If I just use the adjustable objective on the higher power scopes and keep decent form then I have no problems.

I need to get a lot better at doping the wind. That is a much more significant factor than parallax if I just pay a little attention to form and using the AO.
 
Interesting thread. Will one of you please post a picture of the $10,000,000. :)

FWIW - I can clearly see the visual effect called parallax through my Zeiss Conquest 4.5 - 14 scope. It has a parallax adjustment that works really well and it does make a difference in my ability to hit small targets at long distances.
 
Flashhole, your scope doesn't adjust parallax. It only adjusts the objective lens system to focus targets at different ranges in the reticule plane.

As I'm the one who made the ten-million bet, I get to decide what the units are. They ain't money, or any other "valuable" thing. I didn't specify any monetary unit, did I?
 
your scope doesn't adjust parallax. It only adjusts the objective lens system to focus targets at different ranges in the reticule plane.
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Which is how you eliminate parallax.:cool:
Once the 2 image planes coincide there is no parallax.
 
You can also eliminate it by putting your aiming eye on the eyepiece optical axis centrtrd behind it. Even when the scope's not focussed on the target, with that eye so positioned, there is no parallax.
 
Bart B. said:
You can also eliminate it by putting your aiming eye on the eyepiece optical axis centrtrd behind it. Even when the scope's not focussed on the target, with that eye so positioned, there is no parallax.
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Eye on optical axis does not eliminate parallax, but eliminates the error due to parallax, theoretically. Practically it is exactly the point of parallax adjustment. I can't possibly guaranteed my eye is back on the axis shot after shot. The error will therefore be always there.

I may be able to do it when, or if, I one day become a record-breaking, match-winning rifleman. Then I will superglue the parallax knob fixed. Before that I will adjust it before I aim and shoot.

-TL
 
I'll stick with the traditional meaning; parallax is the apparent displacement of observed objects due to a change in the position of the observer's eye. If there's no displacement, there's no parallax.

If you disagree, create your own definitions. It won't change how scopes work; whether they adjust "focus" or "parallax" by their makers' names for what happens inside. They all adjust where the objective lens system focuses light rays from things down range in the eyepiece image plane about the reticule. Then you can adjust your binoculars, spotting scopes and cameras lenses for parallax, too, if that's how you want to understand how optics work. They all work exactly the same way with light rays from stuff very close to far, far, very far away.
 
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Exactly. When the image aligns with the recticle, there will be no image displacement, whether the observer's on axis or not. It is quite simple really.

-TL
 
Bart B, it could be Monopoly money.

Bart, how 'bout a little constructive criticism in the way of a spelling correction. Reticule is spelled reticle. Being the uncontested "Galactic Emperor", I am free to make suggestions such as this.
 
O

Constructive criticism welcomed, Pogybait.

That ten million could also be that many molecules of water.

Reticle = reticule. They're variants of each other. Both are correctly spelled.

https://www.google.com/search?q=reticule&ie=UTF-8&oe=UTF-8&hl=en&client=safari

As is meter and metre; the standard for metric measurements. It's origin was based on a distance between two places on earth ten million meters apart.

I think I'm the only person who tries to get people to spell John Garand's rifle military designation correctly. There's no "-" between the letter and the number. M1.
 
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Bart B. said:
I think I'm the only person who tries to get people to spell John Garand's rifle military designation correctly. There's no "-" between the letter and the number. M1.
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Well, join the club, I think I'm the only person who spells Miniè ball correctly.
 
Bart B, I stand corrected. I appreciate the tremendous response to my question about parallax. Some responses required me to understand quantum physics but I think I have the gist. I think all I need to know is to keep my eye centered in the rear lens.
 
Bart B,

Roger that about the ducks. My comment about quantum physics was a, "tongue in cheek" comment. One of my best attributes is excelling at being a smart ass.
 
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