Search results
Results from the WOW.Com Content Network
That distance is sometimes given on the filter in millimeters. A +3 close-up lens has a maximal working distance of 0.333 m or 333 mm. The magnification is the focal distance of the objective lens (f) divided by the focal distance of the close-up lens; i.e., the focal distance of the objective lens (in meters) multiplied by the diopter value (D) of the close-up lens:
A dioptre (British spelling) or diopter (American spelling), symbol dpt or D, is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dpt = 1 m −1. It is normally used to express the optical power of a lens or curved mirror , which is a physical quantity equal to the reciprocal of the focal length ...
Optical magnification is the ratio between the apparent size of an object (or its size in an image) and its true size, and thus it is a dimensionless number. Optical magnification is sometimes referred to as "power" (for example "10× power"), although this can lead to confusion with optical power .
Illustration of the relationship between optical power in dioptres and focal length in metres. In optics, optical power (also referred to as dioptric power, refractive power, focusing power, or convergence power) is the degree to which a lens, mirror, or other optical system converges or diverges light.
If the difference between the eyes is up to 3 diopters, iseikonic lenses can compensate. At a difference of 3 diopters the lenses would however be very visibly different—one lens would need to be at least 3 mm thicker and have a base curve increased by 7.5 spheres.
The distance between an image and a lens. Real image Virtual image f: The focal length of a lens. Conversing lens Diverging lens y o: The height of an object from the optical axis. Erect object Inverted object y i: The height of an image from the optical axis Erect image Inverted image M T: The transverse magnification in imaging ( = the ratio ...
Parallax compensation control – mean to neutralize the focal difference between the target image and the reticle. All telescopic sights have the first three (diopter, elevation, windage) adjustment controls, and the fourth (magnification) control is offered on variable-power sights.
It is the distance between pupil centers. BVD Back vertex distance is the distance between the back of the spectacle lens and the front of the cornea (the front surface of the eye). This is significant in higher prescriptions (usually beyond ±4.00D) as slight changes in the vertex distance for in this range can cause a power to be delivered to ...