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Diagram of decreasing apertures, that is, increasing f-numbers, in one-stop increments; each aperture has half the light gathering area of the previous one. In optics, the f-number (sometimes called focal ratio, f-ratio, f-stop, or relative aperture[1]) of an optical system is the ratio of the lens's focal length to the diameter of the entrance pupil.[2] It is a dimensionless number that is a quantitative measure of lens speed, and an important concept in photography. Notation[edit] The f-number N is given by where is the focal length, and is the diameter of the entrance pupil (effective aperture). A 100 mm focal length f/4 lens has an entrance pupil diameter of 25 mm. A T-stop is an f-number adjusted to account for light transmission efficiency. Stops, f-stop conventions, and exposure[edit] A Canon 7 mounted with a 50 mm lens capable of an exceptional f/0.95 A 35 mm lens set to f/11, as indicated by the white dot above the f-stop scale on the aperture ring. f/1 = , f/1.4 = , f/2 = , f/2.8 = (i.e .

Diaphragm (optics) A 35 mm lens set to f/8; the diameter of the seven-sided entrance pupil, the virtual image of the opening in the iris diaphragm, is 4.375 mm Most modern cameras use a type of adjustable diaphragm known as an iris diaphragm, and often referred to simply as an iris. See the articles on aperture and f-number for the photographic effect and system of quantification of varying the opening in the diaphragm. Nine-blade iris Pentacon 2.8/135 lens with 15-blade iris In the early years of photography, a lens could be fitted with one of a set of interchangeable diaphragms [1], often as brass strips known as Waterhouse stops or Waterhouse diaphragms. The diaphragm usually has two to eight blades, depending on price and quality of the device in which it is used. In case of an even number of blades, the two spikes per blade will overlap each other, so the number of spikes visible will be the number of blades in the diaphragm used. In 1867, Dr. * In optics, stop and diaphragm are synonyms.

Schärfentiefe - und nicht Tiefenschärfe! Grundlegend gilt es, erst einmal die korrekte Bezeichnung zu bestimmen. Man trifft in aller Regel auf zwei Begriffe, die das gleiche bezeichnen sollen, aber nur einer von ihnen ist korrekt. Zum einen ist es die "Schärfentiefe" und zum anderen die "Tiefenschärfe". Was ist Schärfentiefe Ein optisches System kann immer nur eine Ebene scharf abbilden. Faktoren, die die Schärfentiefe beeinflussen Es gibt verschiedene Faktoren, die Einfluss auf die Ausdehnung der als scharf empfundenen Zone haben: Der Zerstreuungskreis , im Prinzip stellt dieser das Auflösungsvermögen des Bildmediums dar. Bildgestaltung mit Hilfe der Schärfentiefe Die Schärfentiefe hat einen großen Einfluss auf die Bildgestaltung. Genaue Berechnung Die Schärfentiefe läßt sich auch mit Hilfe einer Formel berechnen, hierzu benötigt man zunächst die Hyperfokaldistanz h der gewählten Blenden- und Brennweitenkombination. Rechner für die Schärfentiefe Natürlich kann man sich die Schärfentiefe auch per PC berechnen lassen. Nokia E90

Entrance pupil A camera lens adjusted for large and small aperture. The entrance pupil is the image of the physical aperture, as seen through the front of the lens. The size and location may differ from those of the physical aperture, due to magnification by the lens. The apparent location of the anatomical pupil of a human eye (black circle) is the eye's entrance pupil. 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. The entrance pupil of the human eye, which is not quite the same as the physical pupil, is typically about 4 mm in diameter. See also[edit] References[edit] Jump up ^ Greivenkamp, John E. (2004). External links[edit] Stops and Pupils in Field Guide to Geometrical Optics Greivenkamp, John E, 2004

Aperture A large (1) and a small (2) aperture Aperture mechanism of Canon 50mm f/1.8 II lens, with 5 blades Definitions of Aperture in the 1707 Glossographia Anglicana Nova[1] In some contexts, especially in photography and astronomy, aperture refers to the diameter of the aperture stop rather than the physical stop or the opening itself. For example, in a telescope the aperture stop is typically the edges of the objective lens or mirror (or of the mount that holds it). Sometimes stops and diaphragms are called apertures, even when they are not the aperture stop of the system. Application[edit] The aperture stop is an important element in most optical designs. The size of the stop is one factor that affects depth of field. In addition to an aperture stop, a photographic lens may have one or more field stops, which limit the system's field of view. The biological pupil of the eye is its aperture in optics nomenclature; the iris is the diaphragm that serves as the aperture stop. In photography[edit]

Neutral density filter Demonstration of the effect of a neutral density filter In photography and optics, a neutral density filter or ND filter is a filter that reduces or modifies the intensity of all wavelengths or colors of light equally, giving no changes in hue of color rendition. It can be a colorless (clear) or grey filter. For example, one might wish to photograph a waterfall at a slow shutter speed to create a deliberate motion blur effect. Mechanism[edit] For an ND filter with optical density d the amount of optical power transmitted through the filter, which can be calculated from the logarithm of the ratio of the measurable intensity (I) after the filter to the incident intensity (I0),[1] shown as the following: Fractional Transmittance (I⁄I0) = 10-d, or Uses[edit] Comparison of two pictures showing the result of using a ND-filter at a landscape. Neutral density filters are often used to achieve motion blur effects with slow shutter speeds Examples of this use include: Varieties[edit] See also[edit]

Airy disk Computer-generated image of an Airy disk. The gray scale intensities have been adjusted to enhance the brightness of the outer rings of the Airy pattern. Surface plot of intensity in an Airy disk. Real Airy disk created by passing a laser beam through a pinhole aperture The diffraction pattern resulting from a uniformly-illuminated circular aperture has a bright region in the center, known as the Airy disk which together with the series of concentric bright rings around is called the Airy pattern. Both are named after George Biddell Airy. ...the star is then seen (in favourable circumstances of tranquil atmosphere, uniform temperature, &c.) as a perfectly round, well-defined planetary disc, surrounded by two, three, or more alternately dark and bright rings, which, if examined attentively, are seen to be slightly coloured at their borders. Mathematically, the diffraction pattern is characterized by the wavelength of light illuminating the circular aperture, and the aperture's size. where

Fraunhofer diffraction (mathematics) The equation was named in honour of Joseph von Fraunhofer although he was not actually involved in the development of the theory.[3] This article gives the equation in various mathematical forms, and provides detailed calculations of the Fraunhofer diffraction pattern for several different forms of diffracting apertures. A qualitative discussion of Fraunhofer diffraction can be found elsewhere. When a beam of light is partly blocked by an obstacle, some of the light is scattered around the object, and light and dark bands are often seen at the edge of the shadow – this effect is known as diffraction.[4] The Kirchhoff diffraction equation provides an expression, derived from the wave equation, which describes the wave diffracted by an aperture; analytical solutions to this equation are not available for most configurations.[5] Diffraction geometry, showing aperture (or diffracting object) plane and image plane, with coordinate system. where  is the Fourier transform of A. Another form is:

Optische Linsen | LEIFI Physik Mit diesem qualitativen1 Experiment sollst du erfahren, wie der Zusammenhang zwischen der Gegenstandsweite g (Entfernung des abzubildenden Gegenstands von der Linse) und der Bildweite b (Entfernung des Bildes von der Linse) bei der Abbildung mit einer Sammellinse ist. Darüber hinaus soll der Zusammenhang zwischen Gegenstandsgröße G und Bildgröße B untersucht werden, d.h. es soll herausgefunden werden, wann die Linse vergrößert bzw. verkleinert. 1 Ein qualitatives Experiment zeigt den ungefähren Verlauf von Größen, es werden keine exakten Messungen gemacht. Als Gegenstand benutzen wir ein "leuchtendes F", d.h. eine Anordnung von kleinen Glühlampen, die den Buchstaben "F" darstellen soll Von einem Gegenstand (rot) außerhalb der Brennweite (g > f) erzeugt eine Sammellinse ein höhen- und seitenverkehrtes Bild (grün).