|Spotting Scope Series||Meopta MeoStar S1 75 HD|
Lens diameter represents the second value in product’s name/designation. For example, 10x42 optics have 42 mm diameter of the lens at the front (those that are closer to the viewing object). It is known that the bigger the lens, the more light goes through and the image we see is brighter. All of this, however, depends on the magnification and quality of a certain optical product. Although the bigger lens diameter in binoculars is better, the size adds up on the weight, making it more heavy and difficult to handle. With riflescopes, bigger size of a lens diameter also means more problems with mounting.
The most common lens diameters are 24 mm, 42 mm, 50 mm and 56 mm.
Closest focus distance
Closest focus distance is an important value when watching butterflies, moths or plants at a really close distance. It represents the nearest distance where the viewing object can still be in focus. With binoculars, an excellent viewing distance is from 1.5 m below. If you’re not particularly interested in watching objects at a close range this is an irrelevant factor when choosing a new pair.
Optical products have many lenses in their housing. With each lens about 5% of the light passing through is lost. This can be solved with an application of coatings on the glass surfaces. With years the technology of coatings changed. At first they used only one layer, where the reduction of the loss was to 2% per surface. Today they use multiple layers of coatings where there’s minimal loss of light - 0.1% per surface. The best binoculars have even 95% of the light transmitted to the eye, through all their lenses.
With increasing transmission of the light, the coating is also important as a protectant of the optical glass and to ensure the true color fidelity, so the colors when entering are the same when exiting binoculars/riflescope. Above all, coatings also increase the image quality because all the light bouncing around on the inside can cover up detail and blur colors.
The process of applying coatings has to be precise, otherwise it can contribute to hazy and blurred image. They must be spread evenly and thinly to ensure the best quality. The better the coatings, the more expensive the optical product.
Lens coatings are as important as the quality of the lenses themselves. You can easily check whether your optical product has coatings – if you look at the reflection and it shows multiple colors such as purple, green or yellow the lenses are definitely coated. On the opposite, lenses with no coatings have a clear reflection without showing any colors.
There are many different ways of applying lens coatings:
The waterproof feature is made to keep the optical products sealed and protected from water or dust. Such products are suitable for marine, hunting, hiking or in extreme humidity. Even if you’re not planning on using them in this kind of situations, it is a good feature to have in case of heavy rain or dust. Waterproof optical products are typically sealed with O-rings.
All optical products that are fogproof are also waterproof because they have to be properly sealed to keep the dry gas inside. Yet not all waterproof products are also fogproof as the air inside the product is not necessarily replaced with dry nitrogen or argon.
You should be careful not to confuse waterproof with weather-resistant as they’re designed to protect only against light rain and are not fully sealed.
Slightly better waterproofing of binoculars can also be ensured with an individual eye focusing mechanism, due to less moving parts than with the central focusing system.
Fogging in optical products can occur when you move them from the warm insides of your house to the cold outdoors. To prevent the formation of inside fogging they’re often filled with dry gas – either nitrogen or argon which contain no moisture.
To keep the gas intact on the inside, the optics have to be properly sealed, which is why all fogproof optical products are also waterproof.
It’s important to keep in mind that fogproof means that it’s to prevent fogging on the inside of the optics, not on the outside. If your outside surface of the lenses fogs up due to temperature differences or humidity just allow them to adjust back – do not wipe the condensation off as it can be damaging to the glass surface and its coatings.
|Temperature range||- 25 / + 55°C|
Optical products are often filled with dry gas to prevent the condensation on the inside of the housing when exposing them to temperature extremes. If there is even a slight sign of air inside, there is a certain % of moisture present. Usually they’re filled with either argon or nitrogen gas, which have the same effect – to prevent the moisture and internal fogging without affecting the optical properties. In addition, these gases also prevent the formation of fungus which would destroy the optics. Internal dewing was the biggest problem in older binoculars when exposed to lower temperatures, because they weren’t watertight and contained air. Newer binoculars are therefore all airtight and filled with dry nitrogen or argon.
Objective diameter is outside (housing) diameter of front side (objective) on rifle scope.
On most rifle scopes objective diameter is bigger than tube diameter. Keep in mind, the last number in the description of rifle scope tells you the size of the objective lens diameter (example: 2 – 7 x 32). Objective diameter is always bigger then lens diameter.
Objective diameter is important to know, when buying ring mounts. The bigger the objective diameter the higher mount you will need.
This information is also important for all users of clip-on devices.
Source: Revija Lovec
|In production since|
|Made in||Czech Republic|