Rifle Scopes TPAL and Focusing

[77Bronc]

When I was shooting my SN3 Tpal this morning, I had a target at 25 yards and 100 yards. When switching to the 25 yard target, had to use the Tpal knob to focus. I though the Tpal was for paralax correction, shift of target and not to focus, unless I am getting my x's and y's confused, am I missing something?

77

 

[NoExpert]

Re: TPAL and Focusing

It's not "focusing" the scope, it's putting the scope's lenses on the same viewing plane as the target.

 

[77Bronc]

Re: TPAL and Focusing

Then I am glad I went with the TPal or other option, the ERGO, instead of fixed parallax setting at 100/200 yards.

Thanks,

77

 

[dcjs]

Re: TPAL and Focusing

The reason for parallax and the blurry image ist the same, not having the target image focused in the same plane as the reticle, and side parallax adjustment or adjustable objective allow to adjust exactly for that. So I don't see any reason not to call it a "focus knob".

 

[NoExpert]

Re: TPAL and Focusing

Parallax is the biggest issue close up to say 200 yards, past that isn't not as big an issue. Most makers go parallax free at and beyond 100 yards, inside 100 yards you can have trouble with parallax. What I notice with my ERGO is under 50 yards my eye will start to either focus on the reticle or the image since they aren't on the same plane.

So again, not a "focus" issue, but getting the image and reticle on the same plane.

 

[77Bronc]

Re: TPAL and Focusing

What I was doing today, was shooting at 100 yards at 10X, I had another target in my lane at 25 yards. I was trying to see what the POI was at 25 yards when aiming at center target. I kept the scope at 10X so it was real close for such a large magnification.

I had to turn the TPAL all the way to stop, 30 yards, to get the 25 yard target not to be blurry. With the scope at 10X, and TPAL at 30 yards, the 25 yard target came in real clear.

Call it what you want, I used it to focus/pull in the close target. Now if I had turned down the power some, may not have needed it. I am going to set up some targets in my yard and see. I have a big yard, 2 acres, so I have some room to spread out.

77

 

[dcjs]

Re: TPAL and Focusing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: NoExpert</div><div class="ubbcode-body">So again, not a "focus" issue, but <span style="font-weight: bold">getting the image and reticle on the same plane.</span></div></div>
Again, exactly <span style="font-weight: bold">that</span> is "focus". Your statement is like saying that with a camera getting the image in the sensor plane by adjusting the objective "has nothing to do with focus". It has everything to do with focus.

You are setting your diopter to get the reticle, which has a fixed position in the scope, in focus for your eye. Now for varying distances you need to focus the target image on the reticle plane. At the same time, parallax is eliminated because it is also a byproduct of not having the target image focus in the same plane as the reticle.