World Through The Lens |
World Through The Lens |
PHOTOGRAPHIC GLOSSARY:listing some of the terms you may find on the pages of this website. ACCESSORY SHOE: A fitting on top of a camera, either metal or plastic, which allows accessories to be attached to the camera such as flash gun, viewfinder etc. APERTURE: This is a circular hole in front of the lens which controls the amount of light which is allowed to reach the film. This hole is variable, on all but the cheapest cameras and is measures in 'f' stops / numbers. ASA: ASA stands for American Standards Association. Film speed is measured by its ASA Rating. Generally speaking, the higher a film's ASA number, the faster the film is. (The speed at which the film captures light) For example a film with an ASA rating of 100 is twice as sensitive to light as a similar film which has an ASA rating of 50. ASA has now been replaced by the international standard ISO (see below) but many photographers still refer to ASA (Including myself) ASA rating only applies to exposures between approximately 1/1000 and 10 seconds. Anything after that and the rating becomes relatively meaningless. Most films behave as their reported ASA rating when used in normal, daylight photography, with exposures of up to a few seconds. ASTROPHOTOGRAPHY: The art of photographing the night skies. AUTOMATIC LENS: A lens which remains at full aperture, no matter what the working aperature is set at, until the shutter is released. This allowes optimun focusing withour affecting metering. AUTOWINDER: A mechanism which winds the film on automatically to the next frame when the shutter is released. BACKLIGHTING: Lighting coming from behind the subject. Special care has to be taken during exposure as the light can fool a automatic light meter. BRACKETING: CAMERA: The equipment by which you exposure your films. The camera basically consists of two parts; body and lens. COLOUR BALANCE: The film's ability to record accurate colours. Long exposures can ruin a film's color balance. CONTRAST: How light and dark are recorded by the film. This is affected by the emulsion. (See emulsion below) DEPTH OF FIELD: The distance between the furthest and nearest points of the subject you are photographing that are sharp. Generally speaking this is one third in front of the subject and two thirds behind. DIGITAL: With digital cameras the image is not exposed on film but stored digitally as data which is then generally uploaded to a computer and viewed on screen. EMULSION: The sensitivity of the film also affects the contrast of the film's emulsion. The lower the sensitivity, the higher the contrast recorded by the emulsion. A film which is highly sensitive to light also reproduces less contrast within the image. So a 1600 ASA will have far less contrast than a 100ASA film. EXPOSURE: The time it takes to exposure the film to light in order to get a good photograph. F NUMBERS /STOPS: Numbers on the lens for choosing the aperture size relative to the focal length of the lens. Depending on which way you turn the dial, each f stop either doubles or halves the aperture size, allowing in more or less light.The greater the f number the greater your depth of field. FILM: A thin transparent plastic strip coated with light-sensitive emulsion. Black and white has one layer, whilst colour film has mostly three layers each sensitive to a different colour - usually red, green and blue. The film can be either negative (for prints) or positive (slides / transparencies). FILTER: Filters are added to lens, flash guns, studio lights etc in order to create an effect. EG soft focus, warmth, gradient, starburst, polarisation. They can be coloured glass, gelatin or plastic disks. Filters can also be applied during the printing stage to correct or alter the appearance of the image. 'Effect Filters' are also common elements in modern computer photographic-imaging software, such as Photoshop and PaintShop Pro. GRAINS: Exposed and developed silver halides which form black metallic silver grains which produce the photographic image. Generally speaking the higher the film speed (ASA - ISO) the greater the grain effect. So a 1600 ASA will produce excessive grainy looking images, whilst a 50 ASA will produce fine grain and much better photos. Fast film is used mainly for low light photography; e.g. Astrophotography and dark interiors where flash is not allowed. The film's emulsion's sensitivity to light also influences physical properties, such as grain size. In other words a direct relationship exists between the sensitivity of the film and the apparent size of the silver grains which make up the final image quality. Films which are high sensitivity to light are characterized by larger silver grain particles, whilst The lower sensitivity films produce much smaller grain particles. ISO: International standard for film rating. (Speed) HYPERED: Hypered films have been specially treated to improve their speed and reciprocity characteristics. this process is also known as Gas-Hypersensitization. The film is put into a pressure tank, the air is removed and filled with a Forming Gas. The film is then left in the gas to allow the chemical effect to make the film more sensitive to dim light. Most color films show considerable improvement in sensitivity when hypered. A good hypered film that I use is Kodak Royal Gold 200. LENS: Optical element, usually made of glass which are capable of bending light. They may have single or multiple componants. Lens come in various sizes such as; wide, standard, telephoto, zoom etc. LIGHT BOX: Light boxes are fluorescent tubes that are contained in a box and covered with translucent glass. They are used to easily view negative and positive (slides) films. MANUAL MODE: Manual mode gives you control over certain aspects of the camera's facilities by overriding the automatic function. E.G. F stop, aperture, speed, exposure time. RECIPROCITY LAW: Reciprocity is the ability of a film to hold its speed (ISO rating) during a long exposure. RECIPROCITY FAILURE: Films that slow down as the exposure time increases are said to be suffering from 'reciprocity failure'. For an example a 1600 ASA can, after a few minutes exposure end, up performing like a 100ASA. Different makes of film slwo down at different rates. The information is usually printed on the film box or enclosed leaflet. SHUTTER: Mechanical system that is used to control the amount of time a film is exposed to light. The two most common types are between-the-lens diapham shutter and focal plane shutter. SILVER HALIDES: Light sensitive crystals used in the film's emulsion. They change from white to black metallic silver when exposed to light. SKY FOG: A term used by astrophotographers. Film can record very faint light levels so if you keep the shutter open long enough, it will record that scattered light as well. The atmosphere has a tendency to scatter light and although the sky may look dark, it isn't and if you over-exposure the image will only get worse not better and will produce what astrophotographers call 'sky fog'. The exposure limit seems to be around the 30 minute mark. SPECTRAL ACCURACY: The ability of a film to record colour accurately. |