What does the numerical specification of an optic mean?
The first number in an optical specification represents the magnification of the optic. If the optical device is a fixed magnification it is represented by a single number followed by the letter “x”. If the optical device is a variable magnification it is represented by a set of numbers followed by the letter “x”. The second number in an optical specification represents the diameter of the objective lens in millimeters. For example, 7x50 binoculars means the binoculars have a fixed magnification of 7x with a objective lens diameter of 50mm. Furthermore, 1-6x24 riflescope consists of a 1-6x magnification with a 24mm objective lens.
What benefit do optical coatings provide?
Anti-reflective (AR) coatings increase light transmission, image color, resolution and contrast. Without AR coatings the optics light transmission is significantly degraded. The type and number of coatings makes a difference in the quality of the image. Coated optics provide a single anti-reflective coating on at least one lens. Fully coated optics provide a single anti-reflective coating on all lenses. Multi-coated optics provide multiple anti-reflective coatings on at least one lens. Fully multi-coated optics provide the best light transmission possible and consist of multiple anti-reflective coatings on all lenses.
What is the difference between porro and roof prisms binoculars?
Porro prism binoculars are recognized by the objective lenses being spaced farther apart than the eyepiece. Porro prism binoculars provide a wide field of view and enhanced depth of field. Roof prism binoculars are recognized by the objective lenses being positioned in a straight line, and are generally more compact and rugged than porro prism binoculars.
What is the difference between first focal plane and second focal plane reticles?
In riflescopes, reticles may be located at the First Focal Plane (FFP) or Second Focal Plane (SFP) of the telescopic sight of variable magnification riflescopes. In FFP configuration, the reticle remains at a constant size compared to the target. In low magnification, FFP reticles will appear small but grow in size with the increase of magnification. This is useful in range finding reticles as the mil-radians or MOA dimensions of the reticle stay true to the target thus range finding can be performed at any magnification. In SFP configuration, the reticle remains a constant size to the user while the target size changes. Therefore, range finding can only be performed on a designated magnification as the Mil-radians or MOA dimensions will only be true at a specific magnification. This is commonly at 10x for high magnification scopes or the highest magnification for low magnification scopes.
What does the environmental or IP ratings (i.e. IPX4, IPX6, IP66, IP67) mean?
Sightmark rates their optical devices based on the IEC 60529 Ingress Protection Rating. IP rating is formatted as “IP” followed by two digits. The first digit indicated the level of protection against solids such as dust and dirt. If no rating for solids is provided, an “X” is substituted in this position. The second digit indicated the level of protection against liquids. Products rated IPX4, IPX5, IPX6 are weatherproof/ water resistant and can handle conditions such as rain and splashing water. Products rated IPX7 are completely waterproof and can handle submersion up to 1m of water.
How does night vision work?
Night vision units are used to amplify light energy (photons) from ambient light such as moonlight or starlight. Sightmark night vision units use an electronic photocathode tube or a charge-coupled device (CCD) that converts photons to electrons. In photocathode tubes, the electrons are multiplied thousands of times and converted back into photons through a phosphor screen, which produces an image. In CCD sensors, the captured electrons are sent to a signal processor and then sent to a display to create the image.
What is the InfraRed (IR) illuminator?
The IR illuminator acts like a flashlight when there is little or no ambient light. The beam from the IR illuminator is nearly invisible to the human eye, but can be easily detected by light amplifying devices.
Can I use a night vision unit in sunlight?
Yes, all Sightmark Digital Night Vision units can be used in daylight without any concern of damaging the CCD sensor. Sightmark Night Vision units that use a photocathode tube, however, can only be used at night. Sightmark night vision units come with a peephole lens cover to test the unit in daylight. This cover allows you to see an image through the device without letting too much light energy through the photocathode tube, but it is not recommended to be used for long periods of time in daylight. If you use a night vision device in sunlight without the peephole lens cover, it is possible you could damage the tube.
Why do night vision units have black spots?
Black spots are blemishes in the photocathode tube. These spots are inherent in the manufacturing process, and do not affect the reliability or performance of a night vision device.