Rifle Scopes Newbie question on fixed parallax vs. adjustable

[JesseC92]

Hi guys,
My name is Jesse and I'm really new here. (from New Hampshire) I have a question that probably only a new person would ask. I am looking at the Vortex Viper PST 2.5-10x44 and I notice that it doesn't have side focus. With a scope that has a fixed parallax, is it always focused or how does that work? With a side focus you have to change it whenever you go from, say, 50 yards to 150 yards. Wouldn't the image be blurry going from 50 to 150 with a fixed parallax/focus? This is the scope http://www.vortextactical.com/product/vortex-viper-pst-2-5-10x44-riflescope-with-ebr-1-mrad-reticle Opinions on it would be great too I guess

 

[OPTB]

Re: Newbie question on fixed parallax vs. adjustable

With a scope that has a fixed parallax, say 100 yards, you can use it from 100 yards and beyond with little issue. If you try to focus at a target, say 75 yards or less, the image will may not be clear and the crosshairs can sometimes appear to be moving therefore casuing a POI to be off. This is due to the parallax being set at that further distnace. Rule of thumb is you can use a scope with a fixed parallax beyond that setting, but not below it. With that being said, that Vortex PST with a 100 setting can be used well beyond passing 500-600-and if you have the ability 700 yards and up. Now, a adjustable parallax, either EF or AO, will definitely be better due to being able to adjust the scopes parallax to your specific distance. A SF or AO is also needed for long distance shooters to be as accurate as possible.

Good question! Many people are afraid to ask the difference, but its something everyone needs to learn to be on their A game.


"A vote is like a rifle; its usefulness depends upon the character of the user."

 

[JesseC92]

Re: Newbie question on fixed parallax vs. adjustable

Soooooo.... Say with that scope I had a target at 25 or 50 yards, but it only set on 2.5 power, would the image still be good? just degrade if I had it on a higher power at close range? Or is it just plain unclear under 100 yards?

 

[maladat]

Re: Newbie question on fixed parallax vs. adjustable

Depth of field=ranges at which things are in focus.

A fixed parallax scope will typically have a depth of field that extends out to infinity. The lower you turn the power, the greater the depth of field (closer you can aim and see the target in focus).

With a scope that turns down to 3 power or so I would expect to be able to see fine at 50 yards and probably 25.

The higher the magnification of the scope, the narrower the depth of field and the more parallax errors will hurt you. There are certainly other factors that contribute as well but this is why you rarely see focus/parallax knobs on scopes under 10 or 12 power and almost always on higher power scopes.

 

[kentactic]

Re: Newbie question on fixed parallax vs. adjustable

so for example on the SS10x42HD scope... i would just set the parallax to infinity and it will be good at all ranges beyond 100 yards?

 

[maladat]

Re: Newbie question on fixed parallax vs. adjustable

If it has a parallax/focus knob it is best to actually use it.

If you're going to set it to one value and not change it when you change ranges...

If what you're looking at is in focus, then it's in focus.

If the reticle moves compared to what you're looking at when you move your eye around side-to-side, parallax error is a potential issue. I say "potential" because if you hold your eye in the exact same place every time it doesn't matter how badly adjusted the parallax is. Of course, no one is perfect but with a 10X scope and practice with consistent form in repeatable shooting positions, parallax isn't a huge issue.

 

[misterc01]

A small but important point - Parallax is not a focus issue, it is an issue with your eyeball in relation to the target at different focal lengths. At 100 yards and parallax at 100 yards, the focal point is at the center of the optic, and if you move your eye in relation to the crosshairs, the crosshairs stay centered on the target. At different distance, the focal point is NOT at the center, so if you move you eye around, the cross hairs seem to move and the target looks like it has moved to a different points. A parallax adjust eliminates that issue as you change distance. My particular scope looks to be "out of focus" at 25-about 75 yards, and then get more "in focus as I look at targets farther way.