Parallax vs Focus

[wapiti13]

Confusion of parallax vs focus isn't being helped by the scope companies. Leupold, Sightron, etc. have put the parallax adjustment on the left side of the turret and call it "side focus" in their advertising and descriptions of the new scopes. /ubbthreads/images/graemlins/shocked.gif

 

[hareng]

Two years old but a good thread.

"If the reticle seems to move, there is parallax". So by turning the side wheel on a long depth of field scope it would become parallax free at whatever you are looking at.
Now on shallow depth of field scopes, either side of the parallax setting will be a blur. For instance at 50 yards it will be a blur when looking at something at 53 yards, or 300 and 325 yards! Now setting the pa for infinity whilst looking at close stuff, the ret dont appear to move infering that it focuses on the target as it is already parallax free. Checked clamped in a miller at varying ranges.
I have used an M1 Mark 4 for 5 years, and just about every scope out there and work from low to high as do 100's of people i know and have seen- get the range 2% out and its a miss. Always work from one direction, back it off a bit and try again until satisfied even if its got severe backlash.

I on the other hand have seen and had the misfortune to own/use parallax uncorrectable scopes even though the pa wheel is in focus on the target within a yard- Even at at 50 yards there was 3/4"+ off centre ret movement in all directions dependant where head was, yet alone at a 1000 yards. Had 5 replacement scopes and two repairs nine years ago, all the same. Just intrigued was it incorrectly adjusted/set internally?

 

[LandToSea]

Parallax is not calibrating???

Hey guys! I read your string of posts and found them quite informative as I am currently setting up my new Leo Vari-XIII 3.5-10x40 LR M3. I used Catshooters instructions for setting up the scope and ran into an issue when trying to zero the AO side knob. I focused in on an object at aprox 400M (the farthest I could conveniently find without obstruction) and played with the AO knob as Catshooter instructed. I started at infinity and worked my way back until I was parallax free. I was concerned that this point was at the middle dot on the adjustment knob so I went thru the process again starting back at infinity. The result was the same so I loosened the screws and reset the knob so infinity lined up with the hash mark. Now the knob bottoms out at the low magnification end around the second dot and consequently turns way past the infinity mark on the top end. I called Leupold to ask their feedback and the WOMAN who answered the tech line basically said that the knob is set at the factory and not meant to be adjusted. I obviously mentioned that there is adjustment screws on the knob which usually means they are there to enable adjustment but she stuck to her limited insight. I knew I was not getting anywhere so I came back here to ask the gurus for their guidance. /ubbthreads/images/graemlins/confused.gif Please advise. Thanks!

 

[Guest]

Good information. One thing to note is that not all a/os have lock rings! Leupold learned the importance of the lock ring on their later BR-D model and added a second spring to try to keep the BR shooters happy. Didn't work - keeping them happy that is....

So we can safely say parallax exists in all scopes when viewing at distances outside of the parallax free zone - usually 100yds on North American hunting scopes.

If your shooting at 300 yards plus and are doing it for score on targets you want to eliminate parallax unless you like giving your competitors who have A/Os or Side focuses the advantage /ubbthreads/images/graemlins/grin.gif

Next time your at the range bag your gun and check out the effects of parallax at the different yardages! You'll be surprised, but look to 300 + yards to see the real impacts. You can see them with your 6-20x set at any power in its range. If you like you can even compare or measure the degree of movement at the different powers not only at the max power....

If you can fix your eye to be at the same location each time you pull the trigger, parallax is not an issue. Unfortunately, this is impossible!! /ubbthreads/images/graemlins/grin.gif

 

[700]

Guys & Girls

I have a spread sheet done in Excel which may help people understand the relationship between magnification, objective diameter and parallax.

If anybody wants a copy just email me at [email protected].

Remove the Xs from the email address.

Kindest regards

700

 

[LandToSea]

Any responses, please?

Regarding my previous post I was hoping for some response from Dave and Catshooter
Hey guys! I read your string of posts and found them quite informative as I am currently setting up my new Leo Vari-XIII 3.5-10x40 LR M3. I used Catshooters instructions for setting up the scope and ran into an issue when trying to zero the AO side knob. I focused in on an object at aprox 400M (the farthest I could conveniently find without obstruction) and played with the AO knob as Catshooter instructed. I started at infinity and worked my way back until I was parallax free. I was concerned that this point was at the middle dot on the adjustment knob so I went thru the process again starting back at infinity. The result was the same so I loosened the screws and reset the knob so infinity lined up with the hash mark. Now the knob bottoms out at the low magnification end around the second dot and consequently turns way past the infinity mark on the top end. I called Leupold to ask their feedback and the WOMAN who answered the tech line basically said that the knob is set at the factory and not meant to be adjusted. I obviously mentioned that there is adjustment screws on the knob which usually means they are there to enable adjustment but she stuck to her limited insight. I knew I was not getting anywhere so I came back here to ask the gurus for their guidance. Please advise. Thanks!

 

[270WSM]

Re: Any responses, please?

To me, it sounds like you just set your knob so that your infinity setting is at 400 yards. I know my Nikon tactical at the lowest setting is parallax free at 50 yards (advertised and tested by me). I setup the rest by finding objects at 100, 200, 300, 400, etc.... and figuring where my paralax setting for each was and made a scratch in the side parallax wheel. Make scratches where you see fit (the further the distance, the closer the scratch marks will be so you have to decide what yardages to scratch in). I don't see why you need to loosen the set screw and do all that?????? Good luck with which ever way you go.

 

[hareng]

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.

 

[Jon A]

[ 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?

 

[Bart B]

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.

 

[hareng]

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.

 

[Bart B]

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.

 

[Bart B]

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.

 

[Jon A]

Thanks for the info, Bart.