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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 . Related:  Camera Optics Theory

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. A smaller maximum aperture (larger minimum f-number) is "slow" because it delivers less light intensity and requires a slower shutter speed. A lens may be referred to as "fast" or "slow" depending on its maximum aperture compared to other lenses of similar focal length designed for a similar film format. Lens speed given by the minimum f-number, or alternatively maximum aperture diameter or maximum numerical aperture, is a useful quantitative way to compare similar lenses. Fast lenses[edit]

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. Am wichtigsten ist die Kalibrierung eines Monitors. Was versteht man aber nun überhaupt unter Kalibrierung? korrekte Darstellung wenn jeder Grau-Balken vom benachbarten unterscheidbar ist Monitor ist zu hell eingestellt Monitor ist zu dunkel eingestellt Der Kontrast ist zu hoch eingestellt Messgeräte können dies aber noch genauer Beurteilen. Anbieter von Kalibrierungswerkzeugen: Im (voraussichtlich) letzten Teil geht es dann um Weißabgleich, Gammakurve und Farbraum.

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.

F-stop, una scala che sembra strana La velocità dell’otturatore è molto semplice da capire, ma sono in molti, fra i principianti, a fare confusione con l’indicatore dell’apertura. Sia per i valori che ha la scala utilizzata sia perché a numeri più piccoli corrispondono aperture più grandi. Per esempio chi non conosce la teoria dietro a questi numeri utilizzare f/2,8 sembra un numero strano e scoprire che è più grande di f/4 può complicare ancora di più le cose. Questo numero si chiama rapporto focale, ma lo troverete molto spesso indicato come f-stop e rappresenta una frazione della lunghezza focale. Facciamo un esempio chiarificatore. Se invece avessimo impostato f/8 allora avremmo un’apertura del diaframma di un ottavo di 100mm e quindi 12,5mm. Per esempio se avessimo un 50mm con apertura massima f/0.95 significa che il diaframma potrebbe arrivare a misurare 52,6mm. Veniamo ora al motivo per il quale la scala del rapporto focale usa come misura dei numeri che a prima vista potrebbero sembrare “strani”.

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. An elaborated form of the sunny 16 rule is to set shutter speed nearest to the reciprocal of the ISO film speed / setting and f-number according to this table:[2][3] References[edit] External links[edit]

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. All images in my webpage are intended to be viewed with a color depth of at 24bit (True Color).

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

Esposizione (fotografia) Da Wikipedia, l'enciclopedia libera. Fotografia con un'esposizione di 25 secondi Fotografia con esposizione di 8 secondi L'esposizione è definita come: Bisogna però tenere presente che, mentre per i tempi si usa una scala in cui ogni termine è la metà del precedente (es. 1 sec, 1/2 sec, 1/4, 1/8, 1/16 ecc...) per i diaframmi la scala ha una progressione pari alla radice quadrata di 2: f/1,4, f/2, f/2,8 f/4, f/5,6 f/8, f/11, f/16, f/22, f/32 nella quale il primo termine rappresenta l'apertura maggiore. Il mezzo sensibile, poi, ha una sua caratteristica di "impressionabilità", detta velocità o sensibilità: più alta la sensibilità, minore l'esposizione necessaria per lo stesso risultato finale. Ne consegue che, modificando uno dei tre parametri (diaframma, tempo, sensibilità) si dovrà correggere uno degli altri due in modo da compensare la variazione. Variando il tempo, cambia l'esposizione. La neve può ingannare l'esposimetro a luce riflessa

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. Light rays passing through a small aperture will begin to diverge and interfere with one another. Large Aperture Small Aperture Since the divergent rays now travel different distances, some move out of phase and begin to interfere with each other — adding in some places and partially or completely canceling out in others. Diffraction Pattern For an ideal circular aperture, the 2-D diffraction pattern is called an "airy disk," after its discoverer George Airy. Airy Disk 3-D Visualization Barely Resolved No Longer Resolved The size of the airy disk is primarily useful in the context of pixel size.

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). The Online Lighting Diagram Creator is a personal project that requires a lot of resources to be developed and maintained. If you use the OLDC and are happy with it, I'd love if you would consider donating. Known issues : You can now export to JPEG and generate a URL that allows you to bookmark your diagram.

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]

Il diaframma Il diaframma Per regolare l’intensità del flusso luminoso che attraversa un obiettivo, si usa un dispositivo chiamato diaframma. Il più comune, oggi, è il tipo ad iride che permette facilmente di avere le regolazioni anche sulle aperture intermedie. Ne esistono anche di altri tipi, come ad esempio quello del LensBaby che consiste in una serie di dischi forati. Il diaframma si regola ruotando una ghiera numerata solidale con l’obiettivo sulle ottiche con diaframma manuale. Un 21 mm totalmente manuale impostato a f/5,6, come evidenziato dal punto bianco sopra la scala dei diaframmi. Quest’ottica ha aperture che vanno da f/4.0 a f/22 Ghiera di controllo del diaframma elettrico su una Canon Il numero f Il numero f esprime l’apertura relativa del diaframma, cioè quanta luce fa passare attraverso il suo foro. Ogni incremento di numero f porta una diminuzione dell’apertura. f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f18, f/11.3, f/16, f/22.6, f/32,f/45.2, f/64 … Il numero f/#, a volte scritto come N, vale:

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. Physical properties[edit] The cone shows possible values of wave 4-vector of a photon. A photon is massless,[Note 2] has no electric charge,[13] and is stable. Photons are emitted in many natural processes. The energy and momentum of a photon depend only on its frequency (ν) or inversely, its wavelength (λ): where k is the wave vector (where the wave number k = |k| = 2π/λ), ω = 2πν is the angular frequency, and ħ = h/2π is the reduced Planck constant.[17] Since p points in the direction of the photon's propagation, the magnitude of the momentum is Experimental checks on photon mass[edit]

brenizer methode - oder olébokeh! (sammelthread) - Seite 20 Zitat: Genau richtig erkannt, je mehr Ausmaße man beim Shooting berücksichtigt, desto grösser wird der Ausschnitt und die Bildgrösse. Die Unschärfe und das Bokeh bleiben ja immer gleich. Aber man kann am Ende sich den Auschnitt wählen. Die Entfernung zum Motiv bestimmt die Verzerrung - ob nun Fischauge oder "Miniatureffekt". Sehr nett von Dir! Hier mal der versprochene Vergleich, gestern kurz auf dem Nachhauseweg geschossen - und sorry es ist nur eine schäbige Bank ;-) : Bild 1: Geschossen mit dem Sigma 85mm, 180 Bilder (!) Bild 2. 3er Belichtungsreiche mit dem Canon 35mm 1.4L bei Blende 1.4 Weitaus uninteressanter wie ich finde... Fazit: Bokeh und Blickwinkel gefallen mir beim Multirow-Panorama erheblich besser als beim Einzelbild mit dem Canon 35 1.4L.

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