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F-number

F-number
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 .

http://en.wikipedia.org/wiki/F-number

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Lens speed A fast prime (fixed focal length) lens, the Canon 50mm f/1.4 (left), and a slower zoom lens, the Canon 18–55mm f/3.5–5.6 (right); this lens is faster at 18mm than it is at 55mm. Lens speed refers to the maximum aperture diameter, or minimum f-number, of a photographic lens. A lens with a larger maximum aperture (that is, a smaller minimum f-number) is called a "fast lens" because it delivers more light intensity (illuminance) to the focal plane, achieving the same exposure with a faster shutter speed.

Monitor für die Bildbearbeitung (3) - Fotograf Maik Blume Im dritten Teil geht es nun um die Reaktionszeit und die Kalibrierung eines Monitors für die Bildbearbeitung. Um es gleich vorwegzunehmen, die Reaktionszeit (also die Zeit, die das Panel benötigt für den Wechsel eines Pixels von einer Farbe zu einer Anderen) ist nur sekundär wichtig. Da bei der Bildbearbeitung in der Regel nicht mit schnellen Bildfolgen zu rechnen ist, spielt die Reaktionszeit nur eine untergeordnete Rolle. Anders sieht dies bei der Videobearbeitung aus oder bei Spielen. Da sich bei einem Video bzw.

Sunny 16 rule The basic rule is, "On a sunny day set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in direct sunlight."[1] For example: On a sunny day and with ISO 100 film / setting in the camera, one sets the aperture to f/16 and the shutter speed to 1/100 or 1/125 second (on some cameras 1/125 second is the available setting nearest to 1/100 second).On a sunny day with ISO 200 film / setting and aperture at f/16, set shutter speed to 1/200 or 1/250.On a sunny day with ISO 400 film / setting and aperture at f/16, set shutter speed to 1/400 or 1/500. As with other light readings, shutter speed can be changed as long as the f-number is altered to compensate, e.g. 1/250 second at f/11 gives equivalent exposure to 1/125 second at f/16.

G. Winter: Monitor kalibrieren, zur Schonung Ihrer Augen + um Bilder im Net in optimaler Qualität zu betrachten - werbefoto.at Calibrating Your Monitor: The greyscale step wedge you see displayed above is made of 11 / 17 / 24 individual steps from absolute black on the far left to absolute white on the far right. In order to view my astrophotos found in this website as they are meant to be seen, adjust the brightness and contrast controls on your monitor so that each step is visible and clearly distinctable from the others. For example: If you cannot distinguish the black step from the lighter step to its right, increase the brightness. If the white step cannot be distinguished from the darker step to its left, then decrease the brightness. The step wedge should not have a color tint.

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). One then speaks of a telescope as having, for example, a 100 centimeter aperture. Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks Diffraction is an optical effect which limits the total resolution of your photography — no matter how many megapixels your camera may have. It happens because light begins to disperse or "diffract" when passing through a small opening (such as your camera's aperture). This effect is normally negligible, since smaller apertures often improve sharpness by minimizing lens aberrations. However, for sufficiently small apertures, this strategy becomes counterproductive — at which point your camera is said to have become diffraction limited.

Creator / Home - Online Lighting Diagram Creator - Tools for photographers Photography lighting diagrams made easy with this online tool: use the drop down menus, select objects, drag them, rotate them, change their layers then export your diagram to JPEG or save its URL. v3 beta is now public with iPad support, it includes ability to add notes. Select an image set and objet to add: Online Lighting Diagram Creator by QHphotography.com Your donation is greatly appreciated. A minimum donation of $10 USD is asked for each commercial project (except the use on a photographer website, blog or gallery).

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. Photon Nomenclature[edit] In 1900, Max Planck was working on black-body radiation and suggested that the energy in electromagnetic waves could only be released in "packets" of energy. In his 1901 article [4] in Annalen der Physik he called these packets "energy elements". The word quanta (singular quantum) was used even before 1900 to mean particles or amounts of different quantities, including electricity. Later, in 1905, Albert Einstein went further by suggesting that electromagnetic waves could only exist in these discrete wave-packets.[5] He called such a wave-packet the light quantum (German: das Lichtquant).

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. Lens Genealogy LENS GENEALOGY Part 1by Roger Cicala Where do new lens designs come from?I knew that today’s lenses are all designed using computer programs, but I was surprised to find new lenses aren’t designed from scratch. Designers start with an existing lens design and modify it. Of course, a lens designer doesn’t say “this lens really sucks, let’s use it as our starting point”.

DSLR Magnification By: Nick Rains We live in ‘interesting times’. Not since colour film was introduced has so much controversy raged about photography. The Internet has allowed vast global discussions to ebb and flow like never before and whilst this is great in some respects, the downside is that there is a whole lot of misinformation floating around. Circle of confusion In photography, the circle of confusion (“CoC”) is used to determine the depth of field, the part of an image that is acceptably sharp. A standard value of CoC is often associated with each image format, but the most appropriate value depends on visual acuity, viewing conditions, and the amount of enlargement. Properly, this is the maximum permissible circle of confusion, the circle of confusion diameter limit, or the circle of confusion criterion, but is often informally called simply the circle of confusion.

Depth of field and your digital camera What is depth of field? A photographic lens renders a sharp image of points at one given distance, measured along the lens axis. This distance can be adjusted (the process of focusing). Any points at a different distance will be rendered more or less unsharp, and this unsharpness increases gradually as we move away from the "sharp" focus plane. Within some limits it will be small enough to consider the image of our point "sharp enough" for a given purpose. We are talking here only about the unsharpness due to the subject being out of the focused distance.

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