Rifle Scopes Scope Image Quality Degredation Near Vertical Elevation Limits?

[shaun1826]

I’ve read and heard from scope manufacturers that all optics will always perform at their optimum in the center of their travel range. So given this statement, is the degradation in image quality linear as you move up or down from the center of travel? Or is there just a slight loss of image quality as you move away from the center of travel and then a more sudden loss of quality when you get close to the bottom/top of the total elevation travel limit?

Is the loss of quality trivial? Or is it actually noticeable? If there is a general rule of thumb for scopes that you don’t want to generally get a certain % away from the center of travel, then you could match the slope of your rail to the distances you will normally be shooting and enjoy the best quality image and as much elevation adjustment possible. Conversely, if the loss of image quality is pretty trivial, then why would you not always choose the maximum rail slope that would just barely let you zero therby letting you take advantage of the scopes total elevation adjustment?

For example, lets say I have a scope with 30 Mils of total elevation adjustment. From optical center, that is 15 up and 15 down. Is there a point where there is a notable difference in image quality, say at 10-12 mils down/up from center? I’m sure the quality of the lenses between scopes would affect this somewhat, but my gut tells me there is a generality that could be made as well.

Any optics guru’s know the answers? Thanks in advance.

 

[Tara-iti]

There are other things to consider as well such as looking at the end of your barrel or worse suppresor when you get to the top of your scope. This is worst when the scope is mounted low. Also at the top your windage dialing is very limited. I have 35moa rails on most of my rifles which still allow a 100m zero but allows the maximum use of what you have

As far as optical clarity degredation at the top with my scopes its not something I notice.

 

[Hairy Biker]

I'm afraid you may have opened a popcorn thread with that question.

I'll throw some key words in - spring, tension, recoil, lens, concave.

BR learned long ago to keep the scope elevation and windage central to minimise distortion caused by the lens not being a flat surface (the same as never shoot pistol looking through the top thick bit of your spectacle's lens). Also in the bad old days, elevation travel was pretty short compared with today's offerings. So in longer range disciplines we want our mid-point sweet spot to cover the greatest number of ranges we shoot - hence 20 MOA rails becoming standard.

There is some more technical explanations but a scope is the most delicate part of a rifle and you want, no need, to keep the small metal bits as fatigue free as possible.

And the answer about optical quality is - depends on the brand.

 

[Hollywood 6mm]

I'm afraid you may have opened a popcorn thread with that question.

I'll throw some key words in - spring, tension, recoil, lens, concave.

BR learned long ago to keep the scope elevation and windage central to minimise distortion caused by the lens not being a flat surface (the same as never shoot pistol looking through the top thick bit of your spectacle's lens). Also in the bad old days, elevation travel was pretty short compared with today's offerings. So in longer range disciplines we want our mid-point sweet spot to cover the greatest number of ranges we shoot - hence 20 MOA rails becoming standard.

There is some more technical explanations but a scope is the most delicate part of a rifle and you want, no need, to keep the small metal bits as fatigue free as possible.

And the answer about optical quality is - depends on the brand.

I'd say it's more than brand. Look at companies like Vortex and Bushnell that run multiple different product lines. You certainly wouldn't expect a Crossfire to be on par with a Razor HD Gen2, for example, just because they're both Vortex.

 

[shaun1826]

This thread here, POST #7 is exactly the kind of data point I am looking for! If anyone else has similar examples please list them.

https://www.snipershide.com/shootin...ave-used-both-razor-hd-gen2-vs-atacr.6927918/

 

[patriot07]

It's not the same for all scopes, and it won't be predictable for your gun since you don't know where "zero" on your scope is when it's mounted on your rifle, until you actually mount and zero it.

 

[Esoteric Junkie]

It is always best to be as close to center of axis at your desired shooting distance. This will give the best image quality and tracking. When an appropriate tapered base is selected the normal travel range of most upper end scopes will get you from 100 yards on out to a pretty far distance (1500-1750 yards or so) and still maintain good image quality and tracking. For extreme ranges an adjustable base or prism is best to use as it allows the user to maintain a closer to center setup. The ideal setup is to have the scope centered and use an adjustable mount at all distances. The Ivey allows for this scenario and is adjustable on the fly, however it is big and heavy. YMMV.

EJ

 

[lancetkenyon]

I run a high end scope on a 6CM. Last weekend, we were shooting out to 1500 yards. My scope only has "12 usable MIL" of elevation. Which actually turned out to be 11 MIL of elevation adjustment. I needed 14.5MIL. So I dialed 11, and held 3.5MIL. I saw no degredation in scope clarity. And I made the hit. I forgot to allow for the Coreolis effect shooting due west. With a 2.5 second TOF, I am sure that is where my low impact came from......and I am sticking with that.

 

[shaun1826]

I run a high end scope on a 6CM. Last weekend, we were shooting out to 1500 yards. My scope only has "12 usable MIL" of elevation. Which actually turned out to be 11 MIL of elevation adjustment. I needed 14.5MIL. So I dialed 11, and held 3.5MIL. I saw no degredation in scope clarity. And I made the hit. I forgot to allow for the Coreolis effect shooting due west. With a 2.5 second TOF, I am sure that is where my low impact came from......and I am sticking with that.

What scope do you have?

This is the second posting I’ve seen saying a high end scope didn’t have a drop in quality at the limit of elevation travel (see above to the post I referenced). A person refers to a Vortex Razor Gen 2, which most consider a higher end scope, having a drop in image quality, but not his Nightforce ATACR 7-35.

 

[lancetkenyon]

What scope do you have?

This is the second posting I’ve seen saying a high end scope didn’t have a drop in quality at the limit of elevation travel (see above to the post I referenced). A person refers to a Vortex Razor Gen 2, which most consider a higher end scope, having a drop in image quality, but not his Nightforce ATACT 7-35.

Tangent Theta TT315M 3-15x50 w. Gen 2XR reticle.

 

[shaun1826]

With all the .22LR Vudoo's out there now, anyone doing alot of dialing at distance and noticing anything. If so what scope are you using?

 

[just browsing]

I’ve attempted to test this same premise with multiple optics and varying degrees of elevation built in, and while no 2 scopes are the same, some are definitely better than others.

I currently run a Steiner M7Xi with 20 MOA in the base and 20 MOA in the mount on a 6mm (overkill for sure). I am probably 1 mil away from the bottom of the travel. Scope is advertised with 26 total mils of internal adjustment (it’s actually closer to 27 mils) and I have about 25.5 mils available on the turret. I cannot detect any type of compromised IQ, eye box/relief is consistent, and I can’t see the end of my suppressor on a 28” barrel at any magnification.

With a Razor Gen 2, performing this same test, there was noticeable degradation in eye box/relief and CA control with 40 MOA built in. I was also able to see the suppressor up through about 8x. Obviously this is - again - largely dependent on scope, FOV, etc. and may not be a huge deal for some. But if nothing else, I would say there was a ‘noticeable’ difference in overall performance.

So to conclude, I don’t think there’s a one size fits all answer. The best line of thinking is “it depends.”

 

[CSTactical]

Tangent Theta TT315M 3-15x50 w. Gen 2XR reticle.

I recognize that scope!

 

[pitdog85]

I'm about to test this theory on my own scope. Sightron siii 8-32 is currently on a 20moa base and mounted very low on barrel. With a 100m zero I still have 27moa of down. I'm going to put either a 40 or 45 moa base on it which will leave me 2moa from the bottom and all the elevation up.

 

[Discogodfather]

It all depends on the optical and mechanical engineering. If you take a look at most high end scopes that came out before the recent elevation craze we were looking at around 15-25 mills of adjustment. The market put pressure on manufacturers to push the limits of these optical designs and go into the 30-40 mil realm.

One of the key factors is the angle at which the erector tube is at. If you take a look at some of IIya's excellent videos on youtube, you can get the idea that the focal plane (lets take an FFP scope for an example) of the objective is quite a bit larger than the actual image we see through the scope. All else being equal, we need to make that image smaller in order to allow for more elevation travel because the image is literally floating around inside the larger circle that is the actual focal plane.

When I crank my Razor HD2 and ATACR up to max elevation and then also max out on windage, this is the best way to test optical performance. Both exhibit much more off axis lateral CR. Field curvature also suffers dramatically. Over the last weekend Mark down in Australia confirmed the Valdada G2 between 130-150 minutes is pretty bad.

Take a sheet of paper and draw a 3" grid on it. Use that as a target and see how drastically the field curves towards the edge of the lens. It will kill Christmas tree reticles ability to hold under with a combination of curvature and uncorrected parallax.

Of the high end "super dialers" as I call them with above 100 minute elevations the only one that does not show heavy problems is the Hensoldt 3.5-26 x 56mm. It dials 140 minutes and is good to the edges, but Hensoldt sells this scope for $7000 for a reason.

It means little to a tactical shooter going out past 1500 but when you get into serious ELR dialing and ignoring optical performance issues becomes almost impossible.

 

[Eostech]

F#ck yea
Hensoldt . . .

#exquisitedecadence

 

[shaun1826]

It all depends on the optical and mechanical engineering. If you take a look at most high end scopes that came out before the recent elevation craze we were looking at around 15-25 mills of adjustment. The market put pressure on manufacturers to push the limits of these optical designs and go into the 30-40 mil realm.

One of the key factors is the angle at which the erector tube is at. If you take a look at some of IIya's excellent videos on youtube, you can get the idea that the focal plane (lets take an FFP scope for an example) of the objective is quite a bit larger than the actual image we see through the scope. All else being equal, we need to make that image smaller in order to allow for more elevation travel because the image is literally floating around inside the larger circle that is the actual focal plane.

When I crank my Razor HD2 and ATACR up to max elevation and then also max out on windage, this is the best way to test optical performance. Both exhibit much more off axis lateral CR. Field curvature also suffers dramatically. Over the last weekend Mark down in Australia confirmed the Valdada G2 between 130-150 minutes is pretty bad.

Take a sheet of paper and draw a 3" grid on it. Use that as a target and see how drastically the field curves towards the edge of the lens. It will kill Christmas tree reticles ability to hold under with a combination of curvature and uncorrected parallax.

Of the high end "super dialers" as I call them with above 100 minute elevations the only one that does not show heavy problems is the Hensoldt 3.5-26 x 56mm. It dials 140 minutes and is good to the edges, but Hensoldt sells this scope for $7000 for a reason.

It means little to a tactical shooter going out past 1500 but when you get into serious ELR dialing and ignoring optical performance issues becomes almost impossible.

Disco, thanks for the explanation. Do you work for a scope manufacturer? When you say CR, are you referring to Curvature or is that an abbreviation for Chromatic Abberation? Forgive my ignorance.

 

[Discogodfather]

Disco, thanks for the explanation. Do you work for a scope manufacturer? When you say CR, are you referring to Curvature or is that an abbreviation for Chromatic Abberation? Forgive my ignorance.

Sorry, meant to type CA for chromatic aberration. I worked in the optics field for a few years as a lens technician and a camera company in LA in the film industry, but that was a long long time ago. Now I am just a optics enthusiast, addicted to rifle scopes. I also shoot ELR.