5-mm, or 8-mm mini-lens or pinhole lens views through a small hole, an undesirable porthole effect occurs, which is eliminated by having the lens view through a central hole and a series of concentric holes located around the central hole.
Of the large variety of covert lenses available for the security television industry (pinhole, mini, fiber-optic), this unique, extremely useful product hides the pinhole lens in a ceiling sprinkler fixture, making it difficult for an observer standing at floor level to detect or identify the lens and camera.
When installed, most of the pinhole lens and the entire camera is concealed above the ceiling, with only a modified sprinkler head, a small mirror, and small lens in view below the ceiling.
A more aesthetic and covert camera/lens assembly is made up of a camera, pinhole lens, and small mirror.
A minor disadvantage of all fiber-optic systems is that the picture obtained with these systems is not as clean as that obtained with an all-lens pinhole lens.
Optical speed or f-number is probably the most important reason for choosing one pinhole lens over another.
When viewing through a wall with a wide-angle pinhole lens or mini-lens (3.
Under most conditions, the small-barrel, slow-taper pinhole lens is easier to install and is the preferred type over the wide-barrel, fast-taper shape.
The use of a straight or right-angle pinhole lens depends on the space available behind the barrier for mounting the lens and camera, and on the pointing direction of the lens.