How to Controls for Sport Optics Products

How to Controls for Sport Optics Products?

Adjustment Controls for Binoculars

Binoculars have a few controls to adjust, set, and use them.

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Interpupillary (Inter-ocular) Distance –

IPD is a term used for adjusting the distance between the eyes (distance between the centers of the pupils) to use binoculars properly. This distance varies among individuals and must be correct to use the binoculars.
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A normal range for binoculars is 50mm to 75mm but the range can be somewhat different on certain brands and models or between full size and compacts. Young children may require an IPD close to the 50mm area.

The average pupil distance for adults is about 64.5mm but the distance does vary between men and women and relates to the persons size as smaller IPDs are for diminutive optics

To adjust this distance lift the binoculars up and look through them. Move the two halves of the binocular about the hinge until you see one clear circle of image. Now you are ready to optics

Some binoculars (mainly Porro prism types) have an interpupillary scale on the hinge, note the setting and it will be faster to set up when using the binoculars again.

Focus Knob Types – there are three basic types of focus systems:

A) Center Focus — a central knob (the most common) is used to control the focus mechanism of the binoculars.

Usually the right eyepiece has an individual eyesight adjustment collar (diopter). This permits you to compensate for any vision difference between your eyes.

Some models have the diopter adjustment on the center hinge close to the focus control but unless they have a locking mechanism, they are apt to be moved by accident when focusing. Personally, I prefer the eyepiece type of diopter adjustment as I have used this system for years and like it better.

Several brands have a “click stop” diopter adjustment. You just click to each setting. I do not like these because on many models, the perfect setting for me is between clicks and thus they do not work well for me. Consider also that the setting that works for you may not be at the same click point several years later due to wear of the parts and your best position may be in between clicks.

Some manufacturers offer levers or other devices for obtaining focus faster but these require both hands to focus sharply and they may wear after time. I consider these devices as mainly marketing hype and do not recommend them.

B) Individual Focus — allows extra-precise focusing adjustments for image sharpness and clarity since each optical barrel is focused individually. This type of system is more reliable than center focusing and is used for higher end astronomical binoculars, many marine binoculars and for military use. For subject matter 100 feet (30 meters) or more away with only one person using the binoculars, they are a good choice. For multiple users of the binocular they are not as easy to use due to constant refocusing of both eyes continually.

C) Permanent Focus — Jason Empire, in 1988, made a huge commercial success of binoculars that do not need focusing — they are, in essence, “permanently focused”. Current units are somewhat better than the early models and a few manufacturers are offering this type of binocular but they are not very popular. They are extremely easy to use. The negatives to this type of binocular are that there is no way to adjust for vision differences (they have no diopter adjustment) in a user’s eyes (near focus eyeglass wearers must wear their glasses) and they do not have a close focusing range for birding and other applications. They can be OK for general viewing and sporting events if you have 20-20 vision or close to it.

Some companies with center and/ or individual focusing systems say that once you focus at a certain distance – about 50 to 100 feet (15 to 30 meters) or so away, you now have permanently focused binoculars. They may be pretty close to focus (as any binocular would be) but for critical use in observing objects at various distances, you should refocus for the best sharpness.

Eyepiece and Objective Lens Focusing Methods – you will find advertising of different methods of the eyepiece lenses moving or the objective lenses moving in and out:

External focus — when turning the focusing wheel, the eyepieces move back and forth.

Internal focus — when turning the focusing wheel, you cannot see anything move as the lenses inside the binoculars move.

Objective lens focus – turning the focusing wheel moves the objective lenses in or out.

Many people think the eyepiece internal focus is the best method since the binoculars are exposed less to contaminants. However, the other focus types are very good on most binoculars with the difference being insignificant.


sport opticsMany people think you can just pick up binoculars and look through them and all is OK. Binoculars must be focused before using them or you will not get a sharp focus.

Most people have a slight difference between their left and right eyes and the diopter adjustment corrects for this difference. The diopter scale (on some models) indicates the degree of convergence or divergence of the light waves from the binocular.

sport opticsCenter Focus (by far the most popular type) – use the following steps to achieve focus: (1) shut your right eye, look through the left side (eyepiece) of the binoculars with your left eye at an object at least 25 yards (22.9 meters) away. Rotate the center focusing wheel until the image appears in sharp focus; (2) next, close your left eye and look through the right eyepiece at the same object.

Rotate the diopter control on the eyepiece until the image appears in sharp focus; (3) now look through both eyepieces with both eyes open. Since you have already adjusted the right eyepiece, use only the center focusing wheel to refocus on a new object at a different distance.

Some people advise covering the objective lens of each side with your hand or other object while performing the above focusing adjustment. This way of focusing may be better as your eyes will not have any strain when one eye is closed. However, I prefer the closing of the eye method as I am just used to doing it this way for so long.

Most binoculars have a mark (“ 0”, “Δ”, etc.) on the diopter eyepiece and please make note of the setting once you have achieved the best focus, as it will be easier when you have to refocus in the future.

Note: most binoculars have the diopter on the right eyepiece as described above. However, some binoculars have the diopter adjustment close to (or built-into) the center focusing wheel.

sport opticsIndividual Focus – you must close one eye at a time (it does not make any difference, which is first) and rotate the eyepiece until the image is in sharp focus. When changing distances of various objects observed, you must refocus each eyepiece.

Permanent Focus – there is no focus adjustment.

Helpful Hint – if you normally wear eyeglasses for near sightedness and you remove them to use your binoculars, on some models you may not be able to reach a sharp focus at infinity.



Adjustment Controls for Spotting Scopes Spotting scopes

have just a few controls to adjust, set and use them.

sport opticsFocus Knob Types – spotting scopes either have a single focus knob or on models that are more expensive there may be a dual focus where one knob is for coarse focus and the other is for fine focus. Some spotting scopes use a “barrel band” focusing system, which is a focus ring that revolves around the body.

In general, dual focusing systems are faster and allow for more precise focusing.

All types of focus systems can work well provided they function smoothly. I prefer the dual focus type as it gives me the comfort that I know when I have “best” focus.

Also, consider how many turns of the focus knob it takes to go from near focus to infinity as the fewer turns the better in most situations.

Helpful Hint – if you normally wear eyeglasses for near sightedness and you remove them to use your spotting scope, on some models you may not be able to reach a sharp focus at infinity.

soprt opticsZoom Magnification (Power) Adjustment Ring – this allows you to change from low to high power and anywhere in between when using the adjustment ring that operates the zoom mechanism. The ring is normally marked showing the magnification at various points.

The ring should take some effort to move it as if it moves too easily it is harder to zero in on the exact magnification you want or it could move easily if you accidently touch the ring and change your magnification.

Interchangeable Eyepieces – this allows for changing eyepieces on spotting scopes that allow this. The eyepieces are held in place by a thumb screw( s), they can be threaded on and off, or they may use proprietary bayonet mechanisms.


Photographic Attachments – there are many ways to take images through your best spotting scope, each brand and/ or model may do it differently and you will have to see how to do this by looking at your instruction manual. Most of the attachments are optional items but some may be included with certain brands and optics

Taking images through spotting scopes has become quite popular and the common term is “digiscoping” or “phonescoping” for this activity. There are a couple of ways of doing this:

1.Using a point and shoot digital camera. You can hold your digital camera centered directly behind the eyepiece of the spotting scope and take images. This is not the easiest way to do it, as obtaining focus and holding your camera steady can create problems as you are shooting at high powers. I tried this a few years back a couple of times and did obtain some decent shots but only after a lot of

frustration and experimentation. The most common way is to use a dedicated or universal digital camera adapter. The adapter will have adjustment controls in both axes, in, and out so that you can center and focus the object quite easily prior to taking images. Make sure you follow the instructions supplied by the manufacturer.

2. Using a SLR (Single Lens Reflex) or DSLR (Digital Single Lens Reflex) camera. With this method, you will attach your camera to an adapter. This is accomplished in several different ways depending on the spotting scope you have. Some brands use T-Adapters that thread onto the spotting scope (in various ways) and you then need a T-Ring for your particular brand of camera (to install after removing the camera lens) that adapts to your T-Adapter. Some brands have built-in T-Adapter threads and you then adapt a T-Ring for your particular camera.

3.Smart phones can be attached to many spotting scopes and adapters are available from several manufacturers. This is quite enjoyable as it expands your hobby. There are numerous articles and information online about digiscoping and I suggest you read as much as possible as there are many techniques to use to maximize the quality of your images taken through your spotting scope.

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sport opticsSighting Scopes – these allow you to locate objects easier. Some spotting scopes have a low power finder scope or a small “peep” sight to help you. Some spotting scopes have sighting “lines” near the front of the main tube that are helpful in locating your target.

tripodTripod – optional tripods have various and controls for tilting, raising or lowering the tripod, moving the tripod horizontally, and various locking features. Various tripods have different types of controls and you will have to refer to the instruction manual for your particular tripod. Make sure you use a stable and high quality tripod that will allow you to take advantage of the spotting scope and provide you with vibration free views or images.




Adjustment Controls for Riflescopes

An optical riflescope can have several adjustable controls.

Controls that are near the adjustment turret, close to the center of the main tube body, are for elevation, windage and turret mounted parallax. Controls generally use knobs but some older units can be flat dials with a single slot turned with a coin or a screwdriver and most have caps.

Lockable controls or caps are nice to have so accidental movements are not optics

Controls are made with a high level of precision in machining and assembly in order that they are smooth functioning with little effort as they can affect accuracy. They should be repeatable and consistent —after adjusting the dials for different points of impact, when returning to the first setting it should have the same original reading.

Riflescopes that have hard to turn dials, or have backlash and other issues, can cause the user problems. They should be able to handle operating temperatures from -13 ° to 155 ° F (-25 ° to 68 ° C). Most controls have clicks (audible) but some do not. The sound lets you know you have made an adjustment.

Elevation – term used for vertical (up/ down) adjustment of your riflescope. You adjust the elevation to zero the crosshairs on the target. This control normally sits on the top of the turret. On a small percentage of riflescopes, the elevation knob becomes a bullet-drop compensator for quick elevation adjustments for long-range shots.

Windage – term used for horizontal (left/ right) adjustment of your riflescope. It compensates for the rate and direction of the wind. This control usually sits on the right side of the turret.

sport opticsTurret Mounted (Side) Parallax Control – term that is used for parallax (described fully in Chapter 12) adjustment and it is mounted on the left side of the turret housing. Turning the control moves a focus lens in front of the reticle. This type of parallax adjustment is technically more complex than the AO (Adjustable Objective) type described on the next page and it is more expensive but also more user-friendly because the dial can be read with a nominal movement of your head. Personally, I prefer this type of parallax optics

Variable Magnification (Power) Adjustment Ring – allows you to change from low to high power and in between when using the adjustment ring that operates the zoom mechanism. The ring is normally marked showing the magnification at various points. The ring should take some effort to move it because if it moves too easily it is harder to zero in on the exact magnification you want or it could move easily if you accidently touch the ring and change your magnification.

Focusing – term used for the procedure of focusing the eyepiece (ocular). Some users do not know that a riflescope must be focused to get a very sharp and clear image of the subject on the reticle. Each riflescope needs focusing for your particular eye. Some people write about and believe that eyepiece focusing has something to do with correcting for parallax but this is not true.

sport opticsMany riflescopes have an eyepiece-locking ring. Unscrew the ring a few turns and then turn the eyepiece itself as you look at a distant object (preferably use a sign or other distinctive subject matter) through the riflescope. Several turns may be needed, but once your object is in sharp focus, screw the locking ring back into its locked position. Most riflescopes today have a fast focus ring (called fast focus) at the very rear of the eyepiece that has gained momentum over the last decade. You normally use less than a full rotation to find the sharp focus position. This is the easier type of focus system.

A hint when focusing – to achieve the sharpest focus, go beyond the point you believe is the best focus and then return slowly back to the best focus position. You do this because sometimes we do not recognize the sharpest focus position until we go just beyond it. To check focus, point your riflescope at the sky or a blank wall (50 to 100 yards or meters away) at its highest power and focus the eyepiece until the reticle is in sharp focus.

Focus may stay very sharp during your usage of the riflescope but you will generally have to refocus when changing to high magnification and changing target distances.


sport opticsAdjustable Objective Parallax Control – term used for parallax adjustment, which is a rotatable collar near the front (objective end) of the main tube that when rotated moves the objective lens in and out. It is called “AO” or “A/ O” which stands for adjustable objective lens and used for adjustment of parallax.

Note that both types of parallax controls show distance numbers. However, they are only a guide and not exact settings. Many experienced optics writers note that at low power these controls do not make sense and add weight, bulk, and expense to the riflescope.

When using either type of control, make sure to focus the reticle prior to adjusting the AO or turret to ensure a sharp overall focus.

When first using a riflescope with the above type of controls, turn the dials all the way one way and then the other while counting how many full and partial turns it has. Then cut this number in half, which is the middle, and this is where your adjustments should start and make it easier to use the dials.

Most good quality riflescopes will move the point of impact when you adjust the dials without having to “settle in”. Poorer quality riflescopes may need to be shot a few times first to “settle in” the internal adjustments – some old timers tap their riflescopes with a coin or cartridge case that they feel helps this process.

Reading the Dials

For the elevation and windage knobs, the adjustments are put into fractions of “minutes of angle” or “minutes of arc” with both abbreviated as “MOA”.

If you do your hunting and rely on click adjustments, their accuracy is vital to your success.

Both terms of MOA refer to a 1/ 60th division of one degree of arc (1/ 60 °), known as a “minute”. As the total piece of a full circle, a minute would amount to roughly .0046 percent of it or 0.0166 °.

1 MOA @ 100 yards is 1.0472 inches. MOA changes with distance so it is not a set measurement.

Modifying the standard binocular field of view formula at 1000 yards – a single minute of angle/ arc subtends about 1 inch (rounded but 1.0472 is closer to the real number) at 100 yards.

Therefore, the MOA linear relationship for various distances is 1” @ 100 yards or ½” @ 50 yards, 2” @ 200 yards, 3” @ 300 yards, 4” @ 400 yards and 5” @ 500 yards.

The 100-yard distance is the traditional distance on many target ranges.

Note that on some high-end riflescopes, they use SMOA (shooters MOA) where they use 1MOA = 1” and thus be careful of your calculations.

Fractional divisions on the adjustment dials for each click or graduation on the dial can be from 1/ 8 MOA to 1 MOA but most riflescopes are 1/ 4 MOA. Some users call this the “click value”. This click system makes zeroing and adjustments much easier.

The adjustments must be repeatable. An example with ¼ MOA, one click will get 1/ 4th movement at 100 yards and four clicks should get you 1” of movement at 100 yards and this should be repeatable at all times at different distances.




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