Our Riflescope School is courtesy of Zeiss

Whether you are a novice or seasoned riflescope user, these definitions will assist in understanding the different components and considerations that go into the engineering of quality Zeiss riflescopes.

These concepts apply to all rifle scopes, handgun scopes and air rifle scopes.

Magnification

The most basic characteristic of a given scope, magnification is simply a measure of how many times better you can see an object than with your naked eye. It's typically the first number you see in a scope's name. For example, the Zeiss ZM/Z 6x42 MC has a six-power magnification: Six times better than the naked eye.

Zeiss also offers a line of variable power scopes, which allow a range of magnification for different hunting situations. In these scopes, the first two numbers, separated by a hyphen, indicate the range of magnification. For example, the Diavari C 3-9x36 MC magnification can be adjusted as low as 3x, or as high as 9x.

On all Zeiss variable power scopes, the two designating numbers are listed from lowest to highest in magnification.

Objective Lens Diameter

Field-of-View

his important term describes the actual width of your scope's sight picture at a specific distance. For instance, the Zeiss Diatal ZM/Z 8x56 MC gives you a sight picture that is 15 feet wide at a range of 100 yards.

Field-of-view is a function of magnification and the focal lengths of the objective and eyepiece lenses. But remember this: The higher the magnification, the narrower the field-of-view.

This important term describes the actual width of your scope's sight picture at a specific distance. For instance, the Zeiss Diatal ZM/Z 8x56 MC gives you a sight picture that is 15 feet wide at a range of 100 yards.

Field-of-view is a function of magnification and the focal lengths of the objective and eyepiece lenses. But remember this: The higher the magnification, the narrower the field-of-view.

Twilight Performance

Using the following formulas gives a basic evaluation of low light performance; however, one must keep in mind that they are mathematical formulas and do not take into effect some of the most critical features in optics: glass quality, number of lenses, precision of manufacturing and coatings.

Exit Pupil

This is one measure -- expressed in millimeters -- of the amount of light that reaches your shooting eye.

Eye Relief

This describes the distance between your shooting eye and eyepiece lens. It's an important safety consideration. Because if the eye relief is too short, there's an increased risk of dangerous contact between you and your scope under recoil.

Eye relief is determined by the field-of-view, and by the focal lengths of the objective lens and eyepiece lens. Generally, the higher the magnification and the larger the field-of-view, the shorter the eye relief.

All Zeiss scopes, whether fixed or variable power, have consistent eye relief throughout their power range.

Parallax

Parallax presents itself as the seeming movement of the reticle, in relation to the target, when your eye moves off center of the sight picture. It indicates that the scope is out of focus. Even when parallax-adjusted for a designated distance, there is an inadvertent error at other distances. Parallax worsens at higher magnifications.

Center Tube Diameter

The diameter of a scope's center tube (or main tube) impacts the overall strength and durability of the scope. And it obviously determines the size of bases and rings required for mounting. But beyond that, the center tube diameter must be adequate to allow a sufficient range of windage and elevation adjustment. Zeiss riflescopes have either a 30mm or a one-inch center tube, depending on the model.

Square Reticle Adjustment

The Zeiss approach to altering windage and elevation, where the movement of one adjustment does not alter the position of the other adjustment. Our adjustment range is square, unlike most conventional riflescopes. This offsets the reticle's natural tendency to follow a curving path, which makes it all but impossible to sight-in accurately. What is the result of square reticle adjustment? Maximum adjustment accuracy at all times.

Length

The overall length of a scope, from the leading edge of the objective lens housing to the back edge of the eyepiece housing, can be a determining factor when selecting a scope model. Brush and horseback hunters may favor shorter scopes for their discreet profile. But long-range shooters, such as antelope hunters, might embrace longer models that also deliver greater magnification.

The shortest Zeiss scope is about 11 inches in length, while the longest is about 15 inches.

Weight

The type of firearm you hunt with should be a determining factor where the weight of the scope is concerned. Lightweight mountain rifles, for example, seem to beg for scopes that weigh in at the low end of the spectrum. While more traditional rifles do well with the somewhat heavier options.

Zeiss riflescopes range in weight from about 14 oz. to about 25 oz., depending on the model.

Stray Light

Stray light causes poor image quality.

When light entering the scope reflects off of air-to-glass surfaces, the reflected light eventually exits in the scope in the form of stray light. This unfocused light typically diminishes the image quality of the sight picture.

To limit the detrimental effects of stray light, Zeiss employs the proprietary lens coatings known as T* and MC. Additionally, all interior surfaces are anodized in a matte black finish to prevent reflection of the metal. Also, Zeiss scopes do not contain any lubricants, such as oil, that may leak inside and reflect light. The net result of these manufacturing techniques create an image that is crisp and true to color.

Coatings

As light strikes an air-to-glass surface, a small percentage of light is reflected away to become stray light. This effect is limited when these glass surfaces are treated with a microscopic layer of refractive material, such as magnesium fluoride.

To achieve multicoating, several such refractive layers are applied. When properly applied, coatings can dramatically enhance light transmission properties by delivering more of the available light to the shooter's eye. Zeiss' two proprietary coatings are called T* and MC anti-reflective coatings.

Waterproofing

This describes a scope's ability to remain completely dry on the inside when exposed to moisture or total submersion in water. Zeiss scopes aresealed with O-ring and are filled with 100% arid nitrogen, which also resists all forms of moisture. Zeiss scopes are tested in accordance with German DIN 58 390 80 and ISO 9022, which guarantees that the product will not fog or leak in any way.

Congratulations! You have completed Riflescope School and you get an A+