Optics: Parallax vs Focus

Status
Not open for further replies.
Pete I am glad you mentioned the eye peace with a lens cover with a small hole. I was looking through a spotting scope that had one on it this past weekend and thought it was a great Idea. Was thinking of putting a small in one my rubber lens covers and give it a try.

Hey Boyd have you done an article on this yet.


Joe Salt
 
I must have missed something. Explain to me why you would want or need a lens cover with a small hole in it.

On the rifle scope adjusting thing, my post # 11 on the first page of this thread is about the best that I can explain my method. For those who insist that doing it by the book is the only way, I guess I should repeat, that I start out by doing the very best that I can using the "factory" method, extremely brief glances and all, and only expand the search for the proper eyepiece adjustment after I have determined that peak target sharpness and zero parallax are not at the same point of objective or side focus adjustment. The guys that insist that one should only follow the factory procedure seem to ignore the idea that because of the depth of field of the eyepiece and the eye's ability to compensate very rapidly, that in many cases the factory method will not get one all the way to where he wants to go. I developed my method because I am able, on occasion, able to think and try things that are as the saying goes out of the box. Evidently this is not a universal quality. After I have done my very best to focus the eyepiece on the reticule, there is little point to looking at a blank sky. The rest of the procedure is done on target, and what I am looking for is to see the results of very small moves in the eyepiece adjustment, refocusing the target image after each one, and checking for parallax by moving my eye.
 
Boyd Allen said:
I must have missed something. Explain to me why you would want or need a lens cover with a small hole in it.

I developed my method because I am able, on occasion, able to think and try things that are as the saying goes out of the box. Evidently this is not a universal quality. After I have done my very best to focus the eyepiece on the reticule, there is little point to looking at a blank sky. The rest of the procedure is done on target, and what I am looking for is to see the results of very small moves in the eyepiece adjustment, refocusing the target image after each one, and checking for parallax by moving my eye.
Click to expand...

Boyd 1 Other Guy 0
 
Boyd: I'll give you one reason. When mounting a scope we should strive to have the optical center of the scope centered over the bore. If one mounts a scope and does not do this the odds are reasonably good that the turrets are going to be cranked somewhat off optical center to get the poi to equal poa. Using a rear cover with a small hole in the CENTER can tell you very quickly how far off of optical center your scope is. If you are way off optical center maybe you won't even see the intersection of the cross hairs.

The solution to the above is properly bedding the scope in the mounts so the optical center is where the cross hairs intersect. Tony Boyer has an excellent discussion of how to bed a scope in the rings in his book. bob
 
Bob,
Thanks for the explanation.


When I am mounting a scope on an action for the first time, I usually take the time to center the reticule (reticle?) by rolling the scope in a home made V block fixture, and making adjustments to the turrets, until the aiming point does not move, relative to some point at a distance, as the scope is turned. For situations were I want to check things out before modifying anything, I have an old steel tube weaver that I do not worry about damaging the finish of to check the mounted rings to see how far off of the bore a centered scope is pointing.

The worst case of a faulty action that I have seen, a Savage 110, required that .020 offset inserts be used fore and aft, in Burris Signature Zee rings, with their splits vertical, and the front and rear rings' inserts offset in opposite directions. Now that is crooked. Fortunately my custom actions are pretty straight. For Remington actions Holland Gunsminthing has a base that has an adjustment that takes care of the problem quite cleverly. Sub bases are mounted and their tops made coplanar, then the actual rail is installed, and aligned with the barreled action. His is the only mount of its kind that I am aware of.
Boyd
 
Boyd like Bob said I think its to center your eye up better, cause when I looked through the spotting scope everything look like it was there. I didn't have to worry about eye relief it was there. So the other thing I'm wondering is, will my scope cap be the right thickness to allow this to work right. I have two different capes I can try. Will let you know after this weekend!

Joe Salt
 
Joe,
It takes a reticule to have parallax issues. I would think that for a spotting scope just having what you are looking at in the center of the field of view would take care of any quality of image issues. What you will probably be doing, with an eyepiece cap with a hole in it, is limiting your field of view so that you do not see the results, which are out of sight at the edges, of having your eye too far from the eyepiece. Of course this is just a guess since I have not done the experiment. What I have found is that one can sometimes improve the image of a rifle or spotting scope, by placing an aperture that is slightly smaller than the objective lens, slightly in front of it, in effect doing what photographers call stopping down the lens, or in this place scope. I used a crude version of this to look through several rifle scopes at the range one day, and although the images were excessively darkened, in many cases, their sharpness improved. This did not happen (image improvement) when I tried it on my B&L 4200 series 36x.
Boyd
 
Boyd Allen said:
I must have missed something. Explain to me why you would want or need a lens cover with a small hole in it.

On the rifle scope adjusting thing, my post # 11 on the first page of this thread is about the best that I can explain my method. For those who insist that doing it by the book is the only way, I guess I should repeat, that I start out by doing the very best that I can using the "factory" method, extremely brief glances and all, and only expand the search for the proper eyepiece adjustment after I have determined that peak target sharpness and zero parallax are not at the same point of objective or side focus adjustment. The guys that insist that one should only follow the factory procedure seem to ignore the idea that because of the depth of field of the eyepiece and the eye's ability to compensate very rapidly, that in many cases the factory method will not get one all the way to where he wants to go. I developed my method because I am able, on occasion, able to think and try things that are as the saying goes out of the box. Evidently this is not a universal quality. After I have done my very best to focus the eyepiece on the reticule, there is little point to looking at a blank sky. The rest of the procedure is done on target, and what I am looking for is to see the results of very small moves in the eyepiece adjustment, refocusing the target image after each one, and checking for parallax by moving my eye.
Click to expand...

So in other words, while you understand the directions, you do not practice them. Have you entertained the remote possibility that you've been doing it wrong to begin with and if you actually follow them to the letter of the instructions you get the adjustment you're seeking???
The lens cap wit the hole is effectively a stop down like a camera lens. In high mirage, it gives you another option by changing the depth of field. At 200 yards it's quite handy........even for demanding eyes.
 
I was at the range today with a new Savage Predator Hunter Max-1 in 22-250 and a transferred scope from another rifle. After bore sighting and shooting for groups at 100 yards I remembered how it was mentioned about adjusting contrary to manufacturers suggestions to eliminate parallax and as I looked through the scope you could definitely see the cross hairs moving about when you moved your head side to side. I thought I had taken care of that from the other rifle it was transferred from doing it per Leupold's suggestions.

I began to adjust till the target was sharp but got the worse parallax. I then adjusted the ocular and back to the AO again till all parallax was gone. I'm glad I started reading this thread as it sure made a difference.
 
Tim,
I have helped many other shooters perfect the adjustment of their scopes, and they have been pleased to have them adjusted so that they worked perfectly with regard to target sharpness and parallax. I find your speculation and consistent condescension a little irritating, but am not likely to be very impressed by people who are keyboard aggressive while hiding behind a screen name. You seem to be typical of that type. I am aware of the practice of stopping down the front of a rifle scope for the purpose of increasing depth of field on bright days, and I know that March offers an aperture that screws into the objective end of their scopes (at least some of them). I don't believe that other manufacturers offer this for fixed power scopes. In the past Burris has offered a adjustable internal diaphragm in some of their better variables. I am not sure if they still do.
Boyd

Added later: Col Colt, thanks.

Boyd
 
It sure worked for me and the suggestion was most appreciative. Us poor dumb Southerners are not as hard headed as some Yankees.:eek:
 
Boyd yes I know that it takes a reticule to have Parallax but the field of view was excellent I was just thinking out of the box that it may work with a scope, oh and it seemed easier on the eye. Guess anything is worth a try.

Joe Salt
 
Boyd Allen said:
Tim,
I have helped many other shooters perfect the adjustment of their scopes, and they have been pleased to have them adjusted so that they worked perfectly with regard to target sharpness and parallax. I find your speculation and consistent condescension a little irritating, but am not likely to be very impressed by people who are keyboard aggressive while hiding behind a screen name. You seem to be typical of that type. I am aware of the practice of stopping down the front of a rifle scope for the purpose of increasing depth of field on bright days, and I know that March offers an aperture that screws into the objective end of their scopes (at least some of them). I don't believe that other manufacturers offer this for fixed power scopes. In the past Burris has offered a adjustable internal diaphragm in some of their better variables. I am not sure if they still do.
Boyd
R
Added later: Col Colt, thanks.

Boyd
Click to expand...

Screen name ??? That's my name ace. Keyboard aggressive ?? This would make sense if it were not for two elephants in the room. First, every single optic maker that states directions says the exact same thing, and it has zero to do with demanding eyes. Number two, you actually end up doing the same thing with lots of unneeded steps. With all due respect, this is more about your ego than my ability to relay instruction.
 
Boyd,

Please don't let Tim ? get to you. All the regulars here know enough of your history and qualifications so that we at least respect even if we do or do not agree with your opinions and suggestions. Tim ? on the other hand is not know to us as to his qualifications or agenda. I'll also remind you Boyd that arguing with the convinced is an exercise in futility.

Tim ?,

While I think that you have the right to express your opinion, be advised that attacking the opinions of respected members of the forum does not enhance the validity of your argument or diminish the validity of theirs.

Wilbur,

This thread stated out as a reasonable friendly discussion but has deteriorated to an acrimonious argument as have way to many of late. I do not know why this is happening but his one includes an illustration of one contributing issue - anonymity. The very nature of this type of forum combined with the use screen names provides a place for someone to hide in anonymity and avoid any responsibility or accountability for their own statements. I believe this is a major contributor to the acronimity of many recent threads. If the discussion participants were face to face or at least clearly identified to all then they would be much more tempered and reasonable in their remarks.

Rant over!

Fred Bohl
 
Fred good one I think words just jump out at people sometimes and that starts it off. I just ask if they have a problem, if so prove me wrong.

Joe Salt
 
Fred Bohl said:
Boyd,

Please don't let Tim ? get to you. All the regulars here know enough of your history and qualifications so that we at least respect even if we do or do not agree with your opinions and suggestions. Tim ? on the other hand is not know to us as to his qualifications or agenda. I'll also remind you Boyd that arguing with the convinced is an exercise in futility.

Tim ?,

While I think that you have the right to express your opinion, be advised that attacking the opinions of respected members of the forum does not enhance the validity of your argument or diminish the validity of theirs.

Wilbur,

This thread stated out as a reasonable friendly discussion but has deteriorated to an acrimonious argument as have way to many of late. I do not know why this is happening but his one includes an illustration of one contributing issue - anonymity. The very nature of this type of forum combined with the use screen names provides a place for someone to hide in anonymity and avoid any responsibility or accountability for their own statements. I believe this is a major contributor to the acronimity of many recent threads. If the discussion participants were face to face or at least clearly identified to all then they would be much more tempered and reasonable in their remarks.

Rant over!

Fred Bohl
Click to expand...

I have no opinion. I referenced instructions available to anybody with 6th grade reading ability that universally say the same thing irrespective of manufacturer.
 
So TIM have you had a lot of experience with all brands of scopes and they all adjust the same is that what you are trying to say?

Joe Salt
 
Take TIM out of the equation. You have easy to access instructions vs unneccessary complication. First, check a few sites, its all published. Second, go back to the start of this thread and see how its morphed. This really ain't complicated.
 
P.S. you might also Google "how to focus a scope". You should get a YouTube hit right on top from a USMC sniper. Amazing what you learn in 2 minutes, probably doesn't have demanding eyes, however.
 
Status
Not open for further replies.
Back
Top