What's Most Important in Rifle Scope Quality?

[Bart B.]

Irrespective of the focusing used in a riflescope, the prime concept remains the same. The distance from the ocular (eyepiece?) to the reticle must remain the same...

What if your eye changes or your new glasses' prescription requires the ocular lens be moved a millimeter or two either way?

Or, someone else uses the scope?

If the ocular lens focal length is 50 mm, its center will be up to a few millimeters either way from 50 mm depending on who uses it. They are user adjustable and their position plays no part in where target images are focused.

If you meant the distance from the objective lens to the reticle must remain the same, that's not gonna happen unless several lenses in the scope move as the scope's focused at different ranges to do that. The ocular lens is not one of them.

 

[Turbulent Turtle]

What if your eye changes or your new glasses' prescription requires the ocular lens be moved a millimeter or two either way?

Or, someone else uses the scope?

If the ocular lens focal length is 50 mm, its center will be up to a few millimeters either way from 50 mm depending on who uses it. They are user adjustable and their position plays no part in where target images are focused.

If you meant the distance from the objective lens to the reticle must remain the same, that's not gonna happen unless several lenses in the scope move as the scope's focused at different ranges to do that. The ocular lens is not one of them.

Well then, you refocus the ocular using the built-in diopter control. However, that is not something you want to do every time the distance to the target changes and you adjust the side focus.

The distance from the objective lens to the reticle remains constant. In an adjustable objective lens, you focus the objective so that the object you are aiming at is focused properly on the FFP (and SFP and so on). In some side focus scopes, there is a lens between the objective and the FFP that changes the focus distance to that the aiming point is focused properly on the non-moving FFP (and SFP and so on.)

In the first PDF that lens is located AFTER the FFP and simply changes the focus for the SFP where the reticle is located. This is why it's not usable for an FFP-located reticle because by that time, the merged image of the objective and the reticle has already been formed and it's just a single image at this point.

So, whatever wizardy is needed to eliminate parallax, meaning that the image of the objective is formed on the same plane where the reticle exists, this wizardry must be in front of wherever that reticle is located, not behind it.

 

[Bart B.]

The distance from the objective lens to the reticle remains constant.

Only with scopes with fixed objective lenses, side focus knobs and the reticle in the SFP.

In an adjustable objective lens, you focus the objective so that the object you are aiming at is focused properly on the FFP (and SFP and so on).

As target range gets shorter, the objective lens has to move forward to focus its image at a fixed reticle position in that FFP. That increases its distance to the reticle, wherever it is.

Look at that scope diagram showing front focus points 32 A, B and C (all FFP's) incrementally further back from the objective lens as range decreases.

 

[6BRinNZ]

Why is it that we need to choose between mechanical reliability or optical quality. The two aren't related unless price is brought into the equation.
No one has ever asked me what I would pay for both.

 

[Paddyd]

If you do not have excellent optics, repeat ability, durability AND a no questions asked lifetime warranty you just wasted your money.. Any scope that doesn't have all 4 is junk in my opinion. Never buy a scope that doesn't have a no questions asked warranty. If you buy a cheaper scope and it breaks, in the end will spend at least as much getting a cheap scope fixed than you would have buying that quality scope in the beginning.

 

[bpmoss1]

For SR BR holding POI TRUMPS all.

LR BR as well.