معجم المصطلحات - ٢ - كتاب التصوير الضوئي

Glossary of Terms - 2 - Book of Photography

Color temperature Temperature de couleur An expression (generally in Kelvin) for the quality of continuous spectrum light, and color temperature is based on comparison with a standard source called (black body).

Machine movements
Large-sized professional machines allow movement in the reciprocal positions of objects forward (objective lens holder) and backward (film holder) in order to modify the perspective or to change the distribution of the depth of field. Rotation movements on a vertical or horizontal axis (oscillations) and translation movements perpendicular to the optical axis (off-center) are distinguished.

Color sensitivity Sensibilité chromatique The silver gelatinor bromide emulsion is usually sensitive only to violet-blue radiation in the visible spectrum (and to ultraviolet rays). Color sensitization aims to extend the sensitivity towards long-wave radiation. An emulsion sensitive to both blue-violet and green is called orthochromatic, and an emulsion sensitive to all visible colors is called panchromatic. Organic compounds called sensitizers are used for this purpose.

Monobain A single solution containing both the developer and fixative at once, allowing for rapid chemical treatment and is used only when the conditions of development cannot be adapted to the characteristics of the subject or film.

Stop bath An acidic solution whose purpose is to stop development and neutralize the action of the developer on the emulsion.

Nitric acid A substance used in the composition of emulsions, and in some bleaching solutions, very corrosive.

Acetic acid is used in the stopping solution (stopping the development) to stop the effect of the developer and neutralize its participation in the fixative. A 2% solution is required to stop the developer's action on papers and films. We also find it entering into several acid fixative solution compositions (with sodium sulfite).

Bromohydric acid Acide bromohydrique ... Bagues Allonge A metal cylinder placed between the reflex camera and the objective lens and allows for a significant magnification of the close-up subject by lengthening the distance between the objective lens and the film.

Newton rings Coloured ray rings formed by two transparent surfaces (such as glass) that are not in complete contact.

Cartouche Cartouche is the name given to the cassette containing the 35 mm film widely used with reflex cameras (24 x 36 mm).

Monorail A large-format camera composed of two bodies connected by bellows and which slides on a rail or column or optical table.

Silicium cell The latest innovation in cells, it has a linear response and very low inertia and is several times more sensitive than a cadmium sulfur cell.

Selenium cell Cellule de Silenium A photoelectric cell used in some exposure meters, generates an electric current directly proportional to the intensity of the light it receives, its sensitivity is not convincing in low light.

Cadmium sulfur cell Cellule au Sulfure de Cadmium A photoresistor, powered by a battery and its resistance is proportional to the intensity of the light it receives.

The mixing circle Cercle de Confusion is the image formed by a point on a subject whose diameter is very small so that it mixes with a point on the surface of the sensitive film when this point is outside the limits of the depth of field, the diameter of the mixing circle (variable) is the base value for calculating the depth of field.

Negative drawer chassis A replacement piece that allows the use of flat films (film sheets) in large format cameras.

DIN A German model that characterizes the sensitivity speed of emulsion in photography. It is a logarithmic increase of three exposures (German industrial standard). The speed doubles when we increase the value of (DIN) by three units. 23 DIN film is twice as fast as 20 DIN film, less used in France than the American AZA standard.

Angle of reflection Angle de reflexion The angle formed by a ray reflected from a surface with respect to the normal to that surface.

Angle of view Angle de champ The angle at which the objective lens completely covers a shape, measured by the diameter of that shape.

Angle of incidence Angle d'imcidence The angle formed by a ray of light with respect to the normal to a surface. The angle of incidence is equal to the angle of reflection.

Observation glass - frosted glass Verre de visée Verre dépoli in reflex machines and large machines

The image formed by the objective lens is received on frosted glass, and to improve the quality of the observed image this glass is supplemented with a Fresnel lens (which gives a brighter image, especially at the edges of the field) and with other calibration systems such as the feature scale and micro prisms, etc.

The flexible button Declencheur Souple is movable, allowing the shutter button to be operated in an objective camera on a support, thus helping to prevent camera vibration.

Zoom is the name given to lenses with variable focal length. These lenses contain movable optical elements that allow the focal distance to be changed, allowing the subject to be magnified as desired. The magnification, focal distance and angle of view change in proportion to each other. For two or three years, zoom has been widely used in photography, and in amateur cinema, and all 8mm Super cameras are equipped with zoom lenses.

Aberration is a term used to describe the inefficiency of a lens or group of lenses to form a completely clear image. The point in the subject is not translated into a point in the image.

Chromatic Aberration A term used to describe the inefficiency of a simple lens or a set of lenses to form a clear image of all the colors of the photographed subject despite their being on the same image plane.

Spherical Aberration A mistake in the image resulting from a set of lenses such that the rays falling on its optical axis are unable to form a clear image of the subject.

Tireuse A machine that allows a positive image to be taken in contact with a negative and is currently only used for contact printing.

Spot A common name given to a projector with a Fresnel lens that gives a highly directed beam of light.

Tirage A process for producing positive images from a negative, which can of course be done by contact (by a puller) or by magnification (by a magnifier).

Speed ​​The sensitivity of photographic emulsions to light, expressed in DIN or AZA.

Negatives of selection Negatife de selection Negatife de selection Negatife de selection Negatife obtained by sequentially isolating the primary colors or some values ​​of the positive image or subject. Selection is done in the first case (color selection) using filters and in the second case (relative selection) by variable exposure directed negative.

Negatif A photographic image in which the values ​​of the subject are inverted; this is a natural result of exposure followed by fixation; in a color negative the primary gradations of the subject are translated in their complementary colors.

Barium sulfate A very white body with high reflective energy used as a base for photographic papers.

Ammonium sulfur is used in some color-changing or strengthening compounds.

Cyan is a complementary blue color to red.

Chargeur is the name given to the boxes (cassettes) that allow for rapid charging of simple machines 110 and 123.

Diapositive is a transparent image, often in color, and is often designed for display in a positive slide projector (magic lantern).

Glace is the name given to shiny photographic paper, the smooth layer of raw gelatin is polished by contact with a heated metal plate. Glossy plastic sheets are naturally shiny.

Latent image Image Latente is an invisible image made by photography and which will later appear in the development process.

Optical formula Formule Optique The objective lens is composed of a certain number of lenses, the formula shows this distribution of different lenses, isolated or attached.

Safety light A type of non-actinic lighting used in laboratories that process emulsions that are not sensitive to all panchromatic colors.

Flashlight A short-time artificial light source that shines through a closed transparent holder. Flashlight is distinguished by combustion (combustion of metal in an oxygen atmosphere) and electronic flashlight (electric arc in a rare gas).

Electronic flashlight Flash electronique A lighting device obtained by a sudden (sudden) discharge of electrical energy stored in a capacitor. In a bulb filled with a rare gas, which is xenon.
The same flash tube can give several thousand flashes.

Open flashlight An English expression that refers to the method of taking shots with flashlight (Flash) where several flashes are directed in succession to illuminate different parts of the subject and the device's shutter is open. Open flashlight is only used if the ambient light is very weak.

Parasite light (or intrusive light) is a part of the light that enters the camera and does not contribute to the formation of the image. Parasite light is harmful to the quality of the image as it reduces its contrast and clarity.

Reflected light (Lumiere reflechie) is the light that bounces back from the subject or surface towards the viewer or the camera.

Incident light (Lumiere incidente) is the light that falls on a subject or on an area. High key is an English expression meaning (light values) and means a light image with weak contrast and only carries light gray values ​​in addition to white. Its opposite is a low key layer.

Anti-halo layer Couche anti-halo is a colored layer distributed on the back of the film (or on its carrier) whose purpose is to absorb the rays that penetrate the layers of the film and it repels or reduces the halo.

Low key is an English expression meaning (dark values). It means a light image with weak contrast and only carries dark gray values ​​and black. Its opposite is a high key layer.

Wavelength The distance between two peaks of a sine wave in the electromagnetic spectrum. For the visible light spectrum where the wavelength ranges between 400-700 nanometers we also use the unit angstrom (see this word) The wavelength allows us to distinguish the given radiation and the color associated with it (with the naked eye).

Reflector Reflecteur Any material capable of reflecting light, with varying degrees of transmission.

Opacity Opacity The ratio of the incoming light to the transmitted light in a transparent material. Like photographic film in the processor and the appearance, the density is the tenth logarithm of the opacity.

Lens Lentille An optical element of a homogeneous transparent material that refracts light formed by the intersection of two refractors or by the intersection of a refractor and a plane. Distinguish between converging or positive lenses (biconvex, plano-convex or convex-concave converging) that converge the rays to form a real image, and diverging lenses (or previous ones) biconcave, plano-concave or convex-concave diverging that disperse the rays to form (in some conditions) an imaginary image of the subject. Lens or aberration - prevents it from forming images of acceptable quality in photography and this aberration is partially corrected by narrowing the relative aperture by means of a pupil (in simple machines) and especially by assembling several lenses that form what is called an objective lens (in sophisticated machines and other optical defects devices).

A large-angle lens Objectif grand-angulaire A photographic lens with a focal length shorter than the diameter of the film used and that captures a large field angle.

An objective lens Objectif An optical device, generally formed by assembling several lenses, that has the property of giving a real image of the subject.

A fixed-distance objective lens Objectif a mise au point fixe For a relatively narrow pupil aperture and a relatively short focal distance, you get a completely clear image at all levels from 1.80 m to infinity. This method is used in simple cameras that do not have a distance calibration mechanism.

Some objective lenses in large-scale instruments can be split, giving a lens assembly a longer focal length but with a slight loss in image quality.

Objective lens Télé objectif A lens with a long focal length in which the automatic retraction is less than the focal distance, allowing for less confusing lenses.

Fresnel lens Lentille de Fresnel A device invented by the French physicist Augustin Fresnel that converts a divergent light beam into a parallel beam. The degree lens is used photographically in projectors and from visible glasses in reflective or frosted glass machines.

Depth of field Profondeur du champ The distance between the first clear plane and the last clear plane in a photograph for a specific calibration distance.

Fisheye A photographic lens with a very large viewing angle and a very short focal length that gives an image with a curved perspective - the field angle can approach or exceed 180°.

Shutter Obturateur An automatic device in a camera whose job is to determine the time of the shot and the exposure time required for the film. This time required for the action is called (exposure time) or (shutter speed).

Focal shutter Obturateur Focal A shutter placed in front of the focal plane, hence the name.

Distinguishes the focal shutter with curtains and the focal shutter with metal plates that operate vertically for short exposure times (fast instants). Exposure is made by a slit that exposes the film surface in succession.

Central shutter Obturateur Central A shutter placed inside the photographic lens next to the pupil

iris (iris) and its plates are spaced out from the optical center.

Rinçage A water washing process between two stages of development.

Lavage The washing process in photography aims to rid the emulsion of all traces of residual products, especially salts resulting from the silver halogen in the fixative. Paper washing has now been reduced by the presence of a semi-smooth color carrier for water and chemical products. Insufficient washing causes damage to the image after a medium or long period.

The aperture is the pupil value and is equal to the focal length divided by the pupil diameter, thus
A lens with a focal length of 55 mm and a pupil diameter of 5 mm has an aperture value of 55 ÷ 11 = 5 F.

Air brush A device that allows the use of liquid pigments for retouching or drawing and has another name « aerograph, or brush.

Air bubble Bulle d'air The air bubble is formed on the surface of the emulsion as a result of not moving the subject continuously at the beginning of the development.

Photogramme (light drawing image) A method of photographing silhouettes obtained by placing the subject directly on the sensitive area and exposing both to light and then developing.

Photoflood or (flood lamp) A special lamp for photographing with very high voltage light.

Photomacrography or (magnification photography) Very close-up photography with a magnification ranging between 0.5 and × 10.

Photomicrography or (micrographic photography) photography using a microscope.