معجم المصطلحات - ١ - كتاب التصوير الضوئي

Glossary

Barn-doors A type of wing mounted on projectors to allow the light beam to be directed.

Drying marks Marques de Sechage When a film dries unevenly, it creates areas of variable density that cannot be corrected later. The film must therefore be dried naturally without allowing water to remain in the emulsion for a long time. To obtain natural drying, the films must be squeezed gently or a wetting agent must be used at the end of the wash. Lime water can tear the film to white marks, these marks can be removed by passing it through a slightly acidic solution and then quickly washing it again.

Parallax The difference in distance between the optical axis of the photographic lens and the optical axis of the viewing lens, this parallelism is only found in reflex machines with two lenses and is absent in reflex machines with one lens or large-format cameras. In machines with separate optics, the parallax is corrected for near-distance vision, which are the most common conditions.

ASA American Standard Association. The ASA values ​​adopted in photography allow for distinguishing the speed of film sensitivity, and the higher the speed, the higher the ASA value, and the relationship between them is an arithmetic progression. A film with a sensitivity of 400 ASA is twice as fast as a film with a sensitivity of 200 ASA. The speed in ASA is always recorded on the film cover.

Primary See complementary colors.

Polarization of light The electromagnetic radiation of visible light oscillates according to all levels of vacuum, and light is considered polarized when its formation is limited to radiation oscillating according to one level of vacuum. Light is polarized by reflection from a non-metallic surface or by passing through some materials (polarizing filters) or by transmission from the blue sky.

Glossary of Terms - 1 - Book of Photography

Silver recovery Recuperation de l'argent In the process of processing the colorant, the group of metallic silver and silver halogens that were originally in the emulsion are found in the developing solutions used, especially in fixatives and bleaching solutions; on an industrial scale, this silver is recovered chemically or by electrolysis.

X-rays Rayon-x or X-rays. Weak wavelength electromagnetic radiation that penetrates opaque objects, and the photographic emulsion is very sensitive to these rays, which has allowed the use of radiography in medicine.

High illuminations Hautes lumières Parts of the subject or photographic scene are prepared by the strongest lighting (or brightness).

Development A chemical process that aims to convert the silver halogen imprinted
on a light-sensitive layer into metallic silver that forms the image, the quality of development depends on the nature of the appearance, temperature, movement, and the special nature of the emulsion.

Actinic The property of light to modify light-sensitive materials physically and chemically.

Actinometer (radiometer) An ancient basis for measuring exposure based on the comparison between a specific intensity and the time taken by light to enable an emulsion to blacken directly

at the same intensity.

Chromium and potassium color Alun de Chrom ou de Potassium A preparation used to print and form gelatin separately or in an acidic tanning fixation bath.

Reflex camera A type of camera that uses a mirror to reflect the light beam forming the image onto roughened (sanded) glass or onto the viewing glass. There is a single-lens reflector with an objective lens that can be hidden and a double-object reflector with a fixed mirror behind the objective that is used only to adjust the view.

Complementary colors Two colors are said to be complementary when they add up to form the same color intensity (in the perspective of colored light) white. In photography, the complementary colors of the primary colors are the following:

Primary --- Complementary
Blue ------- Yellow
Green ----- Red Magenta
Red ------ Cyan

Absorption The property of a material not to reflect or transmit certain proportions of spectral radiation.

Angström A unit of length used optically to distinguish the wavelength of radiation. One angström equals 10,000,000 of a millimeter.

Refraction Diffraction The bending of light passing through a narrow opening, such as a stenope (pinhole lens), for example. Refraction reduces the clarity of the image.

Positive Any light image in which the proportions of shadow and light are similar to those of the original subject.

Diffuseur Any semitransparent material that softens the directed light.

Paraphenylene diamine is used in some dilution solution formulations.

Ammonium persulfate is used in some dilution solution formulations.

Potassium bromide is used as a fog suppressant in most development solutions.

Focal length Distance focale The distance between the nodal eminence of an objective lens (or lens) from the main focus when the distance crosses infinity.

Far-focal Longue focale An objective lens in which the focal length is greater than the diameter of the film used. The optical formula of far-focal objective lenses varies according to (models: real far-focal), distance objective lens, objective lens equipped with a light reflector (catadium petri).

Baume du Canada A transparent material with the same refractive index as the lenticular glass. Used to glue lenses to the objective lens.

Potassium bichromate is used to strengthen chrome.

Sodium bichromate is used in some strengthening and bleaching compounds.

Panchromatique is an emulsion sensitive to all the color radiations that make up the visible spectrum (from violet to red).

Caustic potash or potassium hydroxide. A strong base used in active developing solutions.

Focus: The distance between the point of intersection of the emitters in an objective lens (or a normal lens) and the image of a point located at infinity. The principal focus is the focus located on the optical axis.

Borax: A weak base used in some developing solutions and fine grains.

Sodium bisulfite is used to maintain the acidity of acidic fixatives.

Intermittence effect: A series of short exposures to light that do not produce blackening in the sensitive layer, which is aided by continuous exposure to the same lighting values.

The Callier effect A negative image enlarged in an enlarger with a condenser gives images with greater contrast than one enlarged under light. This phenomenon was explained by W.H.Callier.

Ecarts de la loi de reciprocité Variations of the law of exchange Normal emulsions obey the law of exchange between speeds from one second to approximately 1/1000 of a second. Beyond these limits, the theoretical speed of the film decreases, which requires increasing the exposure by widening the pupil or slowing the shutter speed.

Contrast is the difference between the highest and lowest density in a photographic image.

Blanching is a chemical process that converts a silver image into an uncolored silver seat. It is often the first stage of color change or strengthening. It is an important stage of color development.

Fixation is a stage of photographic chemical processing based on dissolving the unexposed silver halogen that remains in the emulsion after development or bleaching. The basic material of the fixing bath is sodium hyposulfite (or ammonium).

Essais experiments A method used when drawing black and white or color) allows determining the exposure conditions that give a correct image.

Granulation A discontinuous (discontinuous) structure of the photographic image resulting from silver particles distributed over the emulsion. Grain is clearly distinguished in intermediate gradations.

Infrared Part of the optical spectrum of electromagnetic waves located beyond the red. Infrared photography is very possible, but with specially sensitized emulsions.

Distortion Aberration of the objective lens causing the straight lines of the subject to be distorted, especially towards the edges of the image.

Agitation A method used during chemical processing to ensure contact between the emulsion and the active solution.

Maquillage The process of correcting errors in a magnified image, to adjust the exposure (increase or decrease) by which we can give a part of the image the desired color value.

Gradation is a term used to judge the contrast of a photographic paper intended for enlargement. Gradation is specified by the manufacturer with numbers from 0 to 5.

Intermediate gradation Modele continu A photograph in which all the subject's illuminances are translated at specific intensities.

Hypersensitization A method previously used to increase the speed of films before they are photographed.

Stabilisation The last stage of processing several colour emulsions, it is also a method of quickly fixing the papers in semi-wet processing.

Equidensity A drawing technique that puts into operation some numbers of selected negatives and allows to obtain an image formed from certain density values ​​or with regular colour gradations.

Irradiation The dispersion of light within the photographic layer. The irradiation resulting from successive rays of light on the silver bromide particles is more visible in fast-sensitive emulsions which are naturally thick.

Solarisation The transformation of the image by increasing the intensity of the exposure, this term also means the effect of (Sabaté) or (partial transformation of the image) obtained by a diaphragm during development.

Diaphragm adjustment The adjustment of the pupil opening towards the narrowest.

Exposition (lighting) The exposure to light is equal to the product of the light intensity and the time of action, the light intensity is controlled by the pupil opening and the shutter speed.

Mise au point The process of ensuring the clarity of the image at a given distance to the subject. The distance is generally adjusted by adjusting the distance of the lens. The film, in other words, adjusting the drag.

Reticulation The wrinkling of gelatin induced by the passage of the film between solutions of different temperatures.

Lens coverage Couverture d'un Objectif An expression indicating the circle of the clear image given by an objective lens for a limited distance - for a machine equipped with movements, the objective must have a coverage greater than that necessary and sufficient to cover the film measurement.

Virage color change is the process of replacing a silver image with another image. It is formed from another chemical compound and this is colored (color change with sulfur, iron cyanide, etc.).

Virage au Cuivre color change is a chemical treatment applied to bromide paper images and gives red-purple gradations.

Iridescence Dispersion is the property of glass to refract light rays of different wavelengths, which spreads the spectrum with its colored compositions (Newton's prism, for example).

Reinforcement is a chemical process to increase the density of a light negative image.

Magnification Agrandissement is the production of an image larger than the original negative, it is an image resulting (from projection).

Activation of solutions Régénération des bains The solutions used by professionals quickly wear out if they are not activated with new solutions calibrated to maintain the stability of their chemical activity.
Activation is only done on significant volumes of solutions.

Color synthesis Reconstituting all the colors of a subject by adding three primary colored lights (additional method) or removing the primary colors from white light with dye or coloring (subtractive method).

Projector A device that allows positive slides to be displayed on a screen, and also means a light device that gives a roughly directed light beam.

Joule A unit of energy used in photography to indicate the theoretical energy of light
Electronic flash One joule is equal to the energy of one watt per second 1 = sw1.

Gelatine A substance of animal nature used as a binding material in photographic emulsions.

Genol A widely used reducing agent that gives rich images with intermediate gradations. It is often used with hydroquinone in formulations prepared for development solutions. It has another name (metol, elone).

Preservative A substance of development materials that prevents rapid oxidation Development analyses. Voile is a term used to denote any photographic density that is not due to exposure in the actual sense. The causes of voile are many, intrusive light, very old emulsion, development voile, atmospheric oxidation, etc.

Black voile is a piece of opaque cloth used by photographers to monitor the image formed on the frosted glass of a large format camera.

Color voile is a colored voile that appears on negatives when the developer is contaminated with a fixer or when the fixer is neutralized by an alkaline participation of the developer, it is not able to stop the development. The voile is pink in transparency and yellow-green in reflection, hence the name.

Chemical voile is a name given to the voile formed as a result of an increase in the development time. Imprinted silver halogen appears faster than unimprinted silver halogen. But if the development has been prolonged and the back temperature is excessive, even unimprinted silver halogen will turn into metallic silver, and this is the chemical voile.

Diaphragm A hollow circle that controls the intensity of light that is allowed to pass through to the objective lens.

Iris Diaphragm iris A metal circle with a variable aperture made up of overlapping blades.