Understanding Scope Specs

[Northcountryman]

Ok, Ill admit it- I dont know squat about scope specs!! lol 

All of the scopes-and rifles, for that matter- were either bequeathed to me with scopes already mounted, or, were purchased and mounted by my Grandfather when I was very young .  So, all Ive ever done is point and shoot!!

I was wondering what some of the specs mean for my scopes; for example, my 22 scope has 4x-32 stamped on its inner ocular circular.  I know what the 4x means , but whats the 32?

Also, how do you determine field of view? Parallax? Also, How do you adjust a scopes magnification ?

 

Thanks

[Culvercreek hunt club]

That is a fixed 4 power with a 32 MM objective. (opposite end from the eye piece).  Typically the larger that number the more light that is let in (generally). glass quality and coatings will have an impact. For instance a really high quality scope with a 32 mm objective may let more light in (and efficiently use it) and give you a clearer image than a lower quality 44 mm objective on a cheap scope. 

A scope that is 2-7x44 is a variable power scope. 2 to 7 times magnification with a 44 mm objective.  bigger objectives typically require higher mounting rings so there is clearance to the barrel. This may not line up correctly for you line of sight. I have big cheek bones and on a monty carlo stock I need higher rings than the average person becasue my line of sight is higher above the barrel. So since I have the clearance I typically use a bigger objective.

Field of view decreases as you increase magnification but comparing a 4x scope of various manufacturers you will see differences in the numbers as well.

To adjust the magnification on a scope there is typically a "ring" at the eye piece that  is labeled and indexed. turn it to increase the magnification to the desire power. 

Edited January 26, 2021 by Culvercreek hunt club

[phade]

Also look up focal planes.

Vortex has a good video on Youtube that explains the differences, too.

Eye relief is another topic to understand.

[sbuff]

Good reading  

A BREAKDOWN OF THE RELATIONSHIP BETWEEN RIFLE SCOPE MAGNIFICATION VS. DISTANCE

The relationship between rifle scope magnification vs. distance is relatively straightforward once rifle scope magnification is explained. The first step to explaining rifle scope magnification is understanding how to read rifle scope magnification from a scope’s specification.

A rifle scope specification includes two numbers. The first number identifies the magnification while the second number identifies the diameter of the objective lens. Thus, a specification of 8.5×50 describes a scope with 8.5× magnification and an objective lens that is 50 mm in diameter. Variable magnification scopes have a specification that describes the range of magnifications provided by the scope. 

RIFLE SCOPE MAGNIFICATION EXPLAINED

The magnification is a physical property of the scope. That is, it is defined by the thickness, curvature, diameter, and material of the lenses and their coatings. Once the physical properties of the lenses and their coatings are known, a set of equations defines the optical properties of those lenses.

The lenses inside a scope perform three primary purposes.

• Magnify the target: The objective lens captures light reflected from the target and bends the light to create a magnified image of the target. Some scopes use multiple lenses to magnify the target.
• Invert the magnified image: The image generated by the objective lens is inverted. An erector assembly contains two lenses that flip the image so that it is right-side-up. The erector assembly can also contain the additional magnifying lenses for a variable magnification scope.
• Focus the image: The ocular lens focuses the image that has been magnified and flipped right-side up for your eye. The diameter of the ocular lens also determines the eye relief – the distance between the scope and your eye from which you can see the full, focused image.

THE MAGNIFICATION EQUATION DETERMINES THE SIZE AND DISTANCE OF THE MAGNIFIED IMAGE

The image viewed through the ocular lens is just that – an image. It is, in this respect, a reflection of reality rather than reality itself. The relationship between the image and the target is linear and proportional. Specifically, the magnification defines the ratio between the focal length of the ocular lens and the focal length of the objective lens. In application, this means that the magnification tells you how the image will differ from the target. A target viewed through a 3× magnification scope will appear to be three times closer than its actual distance – targets at 300 yards will appear as if they were 100 yards away.

As the magnification increases, the apparent distance to the image decreases in direct proportion. Thus, doubling the magnification from 3× to 6× will cause the target’s image to appear half as far away.

As a corollary to this equation, the height of the target will also increase in proportion to an increase in magnification. This means that a doubling of magnification from 3× to 6× will not only halve the apparent distance to the target but also double its apparent size.

PHYSICAL LIMITATIONS OF MAGNIFYING LENSES

Magnification does come with trade-offs. There are many optical limitations and types of distortion that are tied to magnification.

1. CHROMATIC ABERRATION

Chromatic aberration or fringing can occur with any lens, but worsens as magnification increases. You see the cause of chromatic aberration when you see a rainbow or view light through a prism – different wavelengths of light interact with a raindrop or prism differently. This causes white light to break up into its constituent colors. The result is that an image viewed through a lens without correction for chromatic aberration can appear blurry or fringed with purple.

2. FIELD CURVATURE

In scopes with low magnification, field curvature can cause blurriness at the edges of the image. At low magnification, the sharpest focus for the image is closer to a sphere than a plane. Consequently, a target and reticle that are sharp near the center of the image are blurry at the edges of the image.

3. SPHERICAL ABERRATION

As magnification increases, spherical aberration may arise. Spherical aberration happens because light is bent more at the edges of a lens than at the center of the lens. This means that the light from the edges of the lens meets at a slightly different focal point than the light passing through its center. Spherical aberration has the same effect on the image as field curvature – the image may appear blurry at the edges when the center of the image is in focus.

4. FIELD OF VIEW

Field of view can be calculated by dividing the diameter of the objective lens by the magnification. As the magnification increases, the field of view will decrease proportionally since the diameter of the objective lens is a fixed number. This means that less area will be visible as magnification increases.

5. DIMNESS

As lenses thicken, or more lenses are included in the scope, more light will be reflected and absorbed rather than transmitted. Even coated lenses will transmit less than 100% of the light incident on the lens. As a result, higher magnification scopes will produce dimmer images than lower magnification scopes.

MAKING A CHOICE – RIFLE SCOPE MAGNIFICATION VS. DISTANCE

There is a saying that you should choose the magnification that is just enough for you to hit the target. In other words, too much magnification brings in drawbacks, such as weight, complexity, and distortion, that produces diminishing returns for the rifle scope. In fact, many shooters find that they need no more than 10× magnification for targets up to 500 yards away. Many hunters settle on magnification between 4× and 6× since most shots taken during deer hunting season will fall between 100 and 200 yards.

On the other hand, shots taken at longer ranges, shots at smaller targets, or shots from more powerful rifles may call for higher magnification. Smaller targets, particularly stationary targets in precision rifle shooting competitions, will be less subject to losses in field of view and less subject to distortion.

[grampy]

Ask, and you shall receive! The guys above gave great information!

Only thing I will add, is that typically the more a scope costs, the better the internal lenses, coatings and materials. So a scope costing $79 most likely will not perform, or last as long as a scope costing $300 or more. You mostly get what you pay for when purchasing optics.

Also, there are many different types of reticles (the lines you see in the scope) And most shooters have their preferences, depending on what type of shooting will be done. Long or short range, thick or thin, a combination of both, or BDC with dots or lines, for shooting longer known distances.

[Culvercreek hunt club]

I posted this last week I think. once you finally get the scope picked out and mount it, it is imperative that it be adjusted correctly for you. The eye relief mentioned above is critical and tying that to the proper height rings. you should be able tot go through the process below and have a full circle clear view through the scope. When you shoulder a gun you should not have to "adjust" your form to get a full picture through the scope. When It's right it works wonderfully. When it doesn't fit it can be frustrating. 

 

Previous post---

"""I've never had a problem getting on a moving deer with a scope. My father trained me early on on how to do it and it works. Step one and the most important is to have the scope and gun set up and it fits you.  This means the eye relief of the scope, pull of the gun and clarity of the crosshair just to name a few. Time after time with your eyes closed...shoulder the gun and then open your eyes. If you don't see a full scope picture with clear crosshairs something isn't right. repeat...repeat...repeat. 

Once that is good, dry  practice on an object. DON'T shoulder the gun and then try to find the object with the scope. if you keep your eyes laser focused on the object and shoulder the gun, brining it INTO your line of sight the crosshairs are going to be on , or very near the object. Sounds easy, and it is once you train your body and eyes.  You don't even want to blink during this shouldering process.  I promise it will work. """

 

crosshairs can be focused using the ring at the eyepiece. Do this at a solid white background. 

[DoubleDose]

I'll add in some more scope information.  On a variable power scope, as magnification increases the eye relief (distance between eye and ocular lense) decreases.  Also, the image brightness you see is a factor of scope exit pupil diameter.  The human eye pupil is 4-5 mm.  The exit pupil on a scope is determined by dividing the objective diameter in mm by the magnification.  So all else being equal, a variable scope of 4-14x44, will have its brightest image from 4x up to 10 or 11x, after that the brightness diminishes as the scope exit pupil falls below 4 mm.  These are important to understand when shooting long distance, low light, or both.  When it comes to scopes, you get what you pay for.  Good scopes cost good money.

[Five Seasons]

mounting the scope correctly closer or further away to where you "shoulder" your gun is more critical then some people realize. The last thing you want is a big buck coming and and to be fighting with that black halo of death (non technical term) to get the buck properly in your scope. Note that different magnifications seem to affect this too, someone more knowledgeable than me can explain better, but if i remember correctly you start at the highest magnification and then everything under should line up.

sorry for not using technical terms, but sometimes I know that helps others. 

[DoubleDose]

3 minutes ago, Belo said:

mounting the scope correctly closer or further away to where you "shoulder" your gun is more critical then some people realize. The last thing you want is a big buck coming and and to be fighting with that black halo of death (non technical term) to get the buck properly in your scope. Note that different magnifications seem to affect this too, someone more knowledgeable than me can explain better, but if i remember correctly you start at the highest magnification and then everything under should line up.

sorry for not using technical terms, but sometimes I know that helps others. 

...and this needs to be done with the clothing you hunt in (or equivalent).  Do not do this set-up in a t-shirt expect it to be correct in your heavy hunting jacket with three layers under it.

Scopes should be kept at their lowest magnification for that potential jump shot.  If the deer is long distance, you have time to crank up the magnification.  If you crank up the magnification, remember to bring it back down to lowest after.  Many a deer has survived because hunters fail to do this and end up with a jump shot and not being able to get on target due to the excessive magnification.

[Culvercreek hunt club]

16 minutes ago, DoubleDose said:

...and this needs to be done with the clothing you hunt in (or equivalent).  Do not do this set-up in a t-shirt expect it to be correct in your heavy hunting jacket with three layers under it.

Scopes should be kept at their lowest magnification for that potential jump shot.  If the deer is long distance, you have time to crank up the magnification.  If you crank up the magnification, remember to bring it back down to lowest after.  Many a deer has survived because hunters fail to do this and end up with a jump shot and not being able to get on target due to the excessive magnification.

That's why those "evil feature" stocks on the black guns are so nice. 

[Northcountryman]

19 hours ago, Culvercreek hunt club said:

I posted this last week I think. once you finally get the scope picked out and mount it, it is imperative that it be adjusted correctly for you. The eye relief mentioned above is critical and tying that to the proper height rings. you should be able tot go through the process below and have a full circle clear view through the scope. When you shoulder a gun you should not have to "adjust" your form to get a full picture through the scope. When It's right it works wonderfully. When it doesn't fit it can be frustrating. 

 

Previous post---

"""I've never had a problem getting on a moving deer with a scope. My father trained me early on on how to do it and it works. Step one and the most important is to have the scope and gun set up and it fits you.  This means the eye relief of the scope, pull of the gun and clarity of the crosshair just to name a few. Time after time with your eyes closed...shoulder the gun and then open your eyes. If you don't see a full scope picture with clear crosshairs something isn't right. repeat...repeat...repeat. 

Once that is good, dry  practice on an object. DON'T shoulder the gun and then try to find the object with the scope. if you keep your eyes laser focused on the object and shoulder the gun, brining it INTO your line of sight the crosshairs are going to be on , or very near the object. Sounds easy, and it is once you train your body and eyes.  You don't even want to blink during this shouldering process.  I promise it will work. """

 

crosshairs can be focused using the ring at the eyepiece. Do this at a solid white background. 

Great post, but Im not sure what you mean by the "height rings" --whats that?  Are you talking about sight adjustment when you zero it in at the range?

 

[Culvercreek hunt club]

18 minutes ago, Northcountryman said:

Great post, but Im not sure what you mean by the "height rings" --whats that?  Are you talking about sight adjustment when you zero it in at the range?

 

There is usually is a base mount that screws into the gun. the "rings" attach the scope to the base. It clamps around the tube of the scope. Those come in different heights to assure a proper alignment of your eye and scope clearance off the barrel. 

in this picture they are using a 2 piece base so it doesn't run across the opening of the receiver and gives you the most clearance for loading and ejecting. What can happen here though it there is not much adjustment left to slide the scope forward of back to set your eye relief. Setting up a scope and buying the components is a series of trade off's in may cases. 

 

Edited January 27, 2021 by Culvercreek hunt club

[Culvercreek hunt club]

[Northcountryman]

Oh ok, got it.  Is there a standard or normal ring height thats most common ? I would imagine that my ideal would lie somewhere between medium to large.  What size do you use?

 

Again, great posts

Thanks!!

[Culvercreek hunt club]

High's usually. might be good to try one on a gun already mounted and see how they fit. Gun stock differences can make you move up or down a size. 

[onlybrowning]

I think it’s already been said, and I’ll over simplify. Mount your scope as low as possible. This promotes good cheek weld to the stock and offers a better scenario for keeping your scope and barrel close to each other. Think of them as lines that at some point must meet for “zero.”


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