Parallax....who can explain it?
Ok, I have to admit, I don't understand parallax when it comes to scopes. I have heard that rimfire scopes have their parallax set at 50 yards, while big bore scopes have theirs set at 100 yards. What does it all mean???
Chris8161
Admit nothing, deny everything, demand proof!
Chris8161
Admit nothing, deny everything, demand proof!
0
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The waves of light are focused into cones from one lens to the next as they pass through the scope. Then as the light goes through the ocular lens (the one nearest to your eye) the light is focused to a point where if you place your eye, the light will appear to be solid from one side of the scope to the other. As you move your eye front to back away from that point portions of the light will black-out. If the scope had no tolerance regarding eye placement, that is your eye would have to be in the exact position in order to see anything but black, there would be no parallax problem, but it would be very slow because you'd have to move your eye around until it was exactly right before you'd see anything. Since this isn't practical, scopes will have brackets of acceptability regarding a full picture through the scope. So you could have your eye a little to the right, left, up, down, forward or back from the ideal point and still be able to see adequately. The price of this lattitude is that as yhou move your eye around, the reticle will appear to move. To try this, put a scoped rifle in a very solid rest so tghat yhou don't need to hold it, then look through the scope, note where the reticle appears to set on the target or object downrange. Then move your head around and watch how the aim point of the reticle moves about on the target, even though there is absolutely no movement in the rifle and a shot from it would go where the barrel is aimed, regardless of where the reticle happens to be at that time. This is parallax. It can be adjusted to be minimum at certain distances. So the scope will be adjusted for the most likely distance that a rifle will be shot, keeping in mind that the nearer the focus, the greater the distortion, that is the change from 50 to 100 yards will be far greater than the change between 250 and 300 yards. So since a 22 will most generally be shot at 25 yards or so, thats the distance the the minimum parallax is set for. High power rifles will generally be about 100-200 yards, after which, the changes have very little effect. Clear as mud? 0 -
May I try to simplify.
The lenses forward of the crosshair focus the image (at a certian distance*) on the crosshair. The lenses behind the crosshair focus your eye to the crosshair (the focus ring is only to get your view of the X-hair in focus, nothing else). The distance at which both the front and back lenses focus on the crosshair is the "parallax free" distance.
*Items closer than this are focused behind (closer to you) the crosshair, while objects further away are focused in front of the crosshair. Which is why the image can shift, relitive to the crosshair, when you move your eye around (at other than the "P-free" range).
Some guys like a mag full of lead, I still prefer one round to the head.0 -
Thanks for the info...now I get it!
Chris8161
Admit nothing, deny everything, demand proof!0 -
Good info,good explanation. And I used the search feature. KEV is gonna be so proud of me,,,[;)][;)][^][8D]
Thanks for the additional info/replys.[:)]0 -
The effects have been well explained, but to add one more point on the cause- light travels at different speed through glass than through air (for all intents a vacuum). The thicker the glass, the longer it takes to get through. If you had a perfectly flat piece of glass, there would be no parallax; however since parts of the lens are thicker than others, the light waves entering the sides get through the glass faster than those entering the center. The shape of the lens accounts for this to re-focus it all back together. However just like your glasses, that focal point is at a given distance from your eye. Move your head side to side, the image blurs as you are off the point of focus where the waves re-converge. move back or forward and you are off the focal point; either of which means you aren't seeing the image 'straight on' so to speak. 0 -
Used a fixed mag scope it takes all the nonsense & the illimination of error out [;)] 0 -
pictures are often helpful:
http://www.answers.com/topic/parallax
be sure you scroll down a bit.0 -
I'll make is REAL simple.
Ignoring for the moment exactly why it happens, in this context parallax refers to the effect of the crosshairs moving relative to the target/point of impact if you shift your head around relative to the scope.
Obviously, this isn't good for accuracy!
Any given scope should be "tuned" to minimize this effect at a particular distance.
Rimfire scopes are usually adjusted to be parallax free at 50 yards, non-adjustable centerfire scopes to 100 yards, and the best centerfire scopes are parallax-adjustable to any distance you like.
Got it?0 -
To visualize it, I like to think that it puts the crosshairs and the target on the same plane. If they aren't on the same plane, when you move your head, the crosshairs are pointing to another point on the target. 0
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