**focal length**- The f-number ("relative aperture"), N , is defined by N = f/E N , where f is the focal length and E N is the diameter of the entrance pupil. (wikipedia.org)
- Increasing the focal length of a lens (i.e., zooming in) will usually cause the f-number to increase, and the entrance pupil location to move further back along the optical axis. (wikipedia.org)
- The f-number of an optical system such as a camera lens is the ratio of the system's focal length to the diameter of the entrance pupil. (wikipedia.org)
- The f-number N or f# is given by: N = f D {\displaystyle N={\frac {f}{D}}\ } where f {\displaystyle f} is the focal length, and D {\displaystyle D} is the diameter of the entrance pupil (effective aperture). (wikipedia.org)
- A 100 mm focal length f/4 lens has an entrance pupil diameter of 25 mm. (wikipedia.org)

**nodal point**- Panoramic photographers often incorrectly refer to the entrance pupil as a nodal point , which is a different concept. (wikipedia.org)
- Wouldn't it be great if everyone entered their values for their NPP / Nodal Point / Entrance Pupil for lens and camera combinations. (panotools.org)
- Wouldn't it be great if everyone entered their values for their Nodal Point / Entrance Pupil for lens and camera combinations. (panotools.org)

**lens**- The entrance pupil is the image of the physical aperture, as seen through the front of the lens. (wikipedia.org)
- The pupil itself, which lens designers would call the aperture , is in a slightly different location because the image is magnified by the cornea . (wikipedia.org)
- In an optical system, the entrance pupil is the optical image of the physical aperture stop , as 'seen' through the front of the lens system. (wikipedia.org)
- The corresponding image of the aperture as seen through the back of the lens system is called the exit pupil . (wikipedia.org)
- If there is no lens in front of the aperture (as in a pinhole camera ), the entrance pupil's location and size are identical to those of the aperture. (wikipedia.org)
- The second table shows the actual entrance pupil distance which is only dependent on the lens itself. (panotools.org)
- Facing the side of the lens, the distance from the base of the lens to the Entrance Pupil. (panotools.org)
- A negative value means the entrance pupil is before the lens base. (panotools.org)
- A negative value means the entrance pupil is before the lens base, such is the case with many telephoto lenses. (panotools.org)
- This is easy to measure and is dependent only on the camera body The second table shows the actual entrance pupil distance which is only dependent on the lens itself. (panotools.org)
- To calculate the Entrance pupil distance add the Tripod Mount Length (L1) from the camera and the Entrance Pupil Length (L2) from the lens. (panotools.org)
- I just did some measurements and found an Entrance Pupil Length of 47mm for this lens. (panotools.org)
- An entrance pupil at infinity makes the lens object-space telecentric. (wikipedia.org)
- If both pupils are at infinity, the lens is double telecentric (or bi-telecentric). (wikipedia.org)
- Light energy enters the eye through the cornea, through the pupil and then through the lens. (wikipedia.org)
- Treat the lens as if it were a pinhole at distance S 2 {\displaystyle S_{2}} from the image plane (technically, the center of perspective of a rectilinear lens is at the center of its entrance pupil): Now α / 2 {\displaystyle \alpha /2} is the angle between the optical axis of the lens and the ray joining its optical center to the edge of the film. (wikipedia.org)
- The entrance pupil diameter is not necessarily equal to the aperture stop diameter, because of the magnifying effect of lens elements in front of the aperture. (wikipedia.org)

**diameter**- The entrance pupil of the human eye , which is not quite the same as the physical pupil , is typically about 4 mm in diameter. (wikipedia.org)
- Refraction in the cornea causes the effective aperture (the entrance pupil in optics parlance) to differ slightly from the physical pupil diameter. (wikipedia.org)
- The entrance pupil is typically about 4 mm in diameter, although it can range from 2 mm (f/8.3) in a brightly lit place to 8 mm (f/2.1) in the dark. (wikipedia.org)
- The pupil magnification of an optical system is the ratio of the diameter of the exit pupil to the diameter of the entrance pupil. (wikipedia.org)

**magnification**- Exit pupil Transmittance Pupil magnification Greivenkamp, John E. (2004). (wikipedia.org)
- Specifically, coma is defined as a variation in magnification over the entrance pupil. (wikipedia.org)
- The pupil magnification is used in calculations of the effective f-number, which affects a number of important elements related to optics, such as exposure, diffraction, and depth of field. (wikipedia.org)
- For all symmetric lenses, and for many conventional photographic lenses, the pupils appear the same size and so the pupil magnification is approximately 1. (wikipedia.org)

**telescope**- In a refracting astronomical telescope the entrance pupil is identical with the objective. (wikipedia.org)

**lenses**- Most lenses have an adjustable diaphragm, which changes the size of the aperture stop and thus the entrance pupil size. (wikipedia.org)

**aperture stop**- The aperture stop is the aperture setting that limits the brightness of the image by restricting the input pupil size, while a field stop is a stop intended to cut out light that would be outside the desired field of view and might cause flare or other problems if not stopped. (wikipedia.org)

**size**- In photography, the size of the entrance pupil (rather than the size of the physical aperture itself) is used to calibrate the opening and closing of the diaphragm aperture . (wikipedia.org)
- Similar to the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock. (wikipedia.org)
- The size of the pupil, which controls the amount of light entering the eye, is adjusted by the iris' dilator and sphincter muscles. (wikipedia.org)
- As soon as the eye moves rapidly to acquire a target (saccades), it re-adjusts its exposure by adjusting the iris, which adjusts the size of the pupil. (wikipedia.org)
- Another consequence of this design is that the entrance pupil varies in size during the tracking of a target. (wikipedia.org)

**angle**- The geometric location of the entrance pupil is the vertex of the camera's angle of view and consequently its center of perspective , perspective point , view point , projection centre or no-parallax point . (wikipedia.org)
- When viewed at large angles from the side, the iris and pupil may still be visible by the viewer, indicating the person has peripheral vision possible at that angle. (wikipedia.org)
- In this case, the solid angle of interest is the solid angle subtended by the optical system's entrance pupil. (wikipedia.org)
- This has the effect of changing the entrance pupil shape as a function of angle (resulting in the path of light being partially blocked). (wikipedia.org)

**Database**- The Entrance pupil database needs constant enhancement. (panotools.org)

**center**- The outside world appears to be seen from the point at the center of the entrance pupil. (wikipedia.org)
- The iris is the pigmented circular structure concentrically surrounding the center of the eye, the pupil, which appears to be black. (wikipedia.org)

**distance**- They must be designed for optimal performance for a specific distance to this entrance pupil (i.e. with minimum aberrations for this distance). (wikipedia.org)

**image**- The entrance pupil is usually a virtual image: it lies behind the first optical surface of the system. (wikipedia.org)

**human eye**- The apparent location of the anatomical pupil of a human eye (black circle) is the eye's entrance pupil. (wikipedia.org)
- In the human eye, the pupil is the aperture. (wikipedia.org)

**optical systems**- Eyepieces are optical systems where the entrance pupil is invariably located outside of the system. (wikipedia.org)

**back**- whereas with a microscope eyepiece the entrance pupil is close to the back focal plane of the objective, mere inches from the eyepiece. (wikipedia.org)

**field**- The 200 mm lens's entrance pupil has four times the area of the 100 mm lens's entrance pupil, and thus collects four times as much light from each object in the lens's field of view. (wikipedia.org)