There are no specific British Standards for control panels (or alarm devices themselves), although elements of BS 4737 relate to features found in alarm equipment. This is likely to change with the introduction of European Standards which will, for the first time, require individual components to meet levels of performance and construction.
It is very important to understand how an alarm system is operated if false alarms are to be avoided. To reduce this risk, manufacturers have been making instructions easier to follow and many panels now incorporate a Liquid Crystal Display (LCD) giving plain English step- by-step instructions to guide users through the arming, resetting and disarming procedures. Read the rest of this entry »
The most important additions to the camera outfit are the extra lenses. If you have always used a standard lens on your camera, you may not find it easy to decide which would be the best lens to buy next. Obviously, you want to start with the one that will be the most versatile for your type of photography. As a first buy, most photographers choose a wide angle lens (28mm) or a telephoto lens (135mm). If you like taking scenic landscape pictures or you want to include a wide area without having to step back with the camera too much, then a wide- angle lens is a good choice. Read the rest of this entry »
The biggest attraction of a 35mm single lens reflex camera is its versatility. Not only is it a useful piece of equipment in its own right, but it can be the ‘heart’ of a complete camera outfit. You can add things like extra lenses, filters, a flashgun, a tripod, as and when you feel you need them, to help you get the results you want.
Smaller items—a blower brush for cleaning lenses, or a cable release, for example—also form part of the serious photographer’s equipment as the collection builds up. And, of course, you will need a gadget bag, or a carrying case to keep everything in. Read the rest of this entry »
Even the most accurate through the lens exposure meter can be fooled by a subject surrounded by large dark or light areas, subjects which are predominantly back lit, or those against unusual backgrounds. These can influence the meter, providing false information about the light level. Thus the main subject is over-exposed if the meter reacts to a large expanse of black background and, conversely, underexposure of the subject results if it is back lit or surrounded by a large bright area. Read the rest of this entry »
Apart from the shutter release, film winder, focusing and exposure controls, even the simplest cameras have a few additional knobs and switches that are either safety devices or provide an extra degree of control. Used correctly they may not only make picture taking more reliable but can also increase the versatility of the camera.
Here’s how to use the extras most commonly found on modern cameras, and in some cases what you can do if your own camera lacks them. Read the rest of this entry »
Exposure meters indicate light intensity and are designed to help you get a correct exposure every time you take a photograph. When a light reading is taken the meter indicates the correct adjustments needed to the camera aperture and shutter speed settings. This sounds simple, as indeed it is, but not all subjects can be treated in a straightforward way. How would you tackle a backlit subject, a snow scene or subjects in deep shadow, for example? In such situations your exposure meter can well mislead you into giving the wrong exposure. ‘Correct‘ exposures are a matter of interpreting meter readings and applying them to the subject in hand. Read the rest of this entry »
A few sophisticated automatic cameras have a dual metering system, one to provide guidance to the photographer in the form of a viewfinder exposure display, while the other system takes a reading of light reflected from the film plane during exposure. The Olympus OM2n is an example where CdS cells provide viewfinder information while silicon cells control the exposure when the camera is set to automatic. Read the rest of this entry »
Most modern cameras have a light meter built in. This has proved to be very popular among amateurs and professionals alike because of the speed and convenience it offers.
All exposure meters work towards the same end—to give the photographer exposure information—but the ways in which they operate vary widely. There are two basic types however: coupled and uncoupled. Examples of both systems are found in 35mm reflex and non–reflex as well as in smaller and larger format cameras. Read the rest of this entry »
You can measure the light either from the camera position or from close to the subject. The reading can be taken in two ways: using the light reflected from the subject or the incident light falling on the subject. Incident light readings can only be taken using a hand-held meter.
A reflected light reading, taken by both built-in and hand-held meters, measures the light bouncing off the subject. It can he measured either from the camera position, where you will actually take the photograph, or close to the subject. Taking the reading from the camera position will give an overall impression of the available light, including the background. But, if one part of the picture is more important than the rest, walk up to it and take the reading, or measure the light on a substitute. For example, a hand held close to the meter will represent skin tones in a portrait if similarly lit. Read the rest of this entry »
Choosing the best exposure for a picture is just as important as getting the image sharp. A beautiful holiday picture on the beach is spoiled if you cannot see details of the people in the photographs—they may be too light or dark.
A correctly exposed negative or slide will have a full range of tones from deep shadows to bright highlights. Under-expose your photograph and the darker parts of the picture will contain little detail; over-expose, and the bright parts will appear all washed out and lacking in detail. Read the rest of this entry »
Basically, there are two main types of shutter: those that work inside or just behind the lens, known as between lens shutters, including sector shutters; and focal plane shutters, which are positioned close to the film.
The between lens shutter closely resembles the aperture and is positioned between the lens elements, near the aperture blades. It is made up of two or more overlapping metal blades. which spring open for the time of the exposure and then close again. These shutters are very light and compact, and can synchronize with flash at all speeds. But between lens shutters have two drawbacks: few work at speeds of over 1/500, and they are costly to produce for cameras with interchangeable lenses. This is because each lens requires its own integral shutter and a separate means to block light from the film when the lens is removed.
Between lens shutters are used mainly on rangefinder 35mm cameras and roll film cameras. Read the rest of this entry »
When you open the back of a camera to change the film, look inside and then press the shutter release. As the shutter opens the aperture can be seen beyond it. This shows more clearly if you look through the front of the lens or, on a camera with interchangeable lenses, take the lens off and look through that. Turn the aperture control and the size of the aperture will alter within the lens as you change the settings.
As the size of the aperture changes, so does the brightness of the light allowed through the lens. Aperture size, and therefore brightness, is controlled by the iris diaphragm, made up of a number of thin, interleaving blades which rotate to make the aperture larger or smaller. Making it smaller (stopping down the lens) reduces the amount of light reaching the film; increasing the size allows more light through. Read the rest of this entry »
The angle of view, or the amount of a scene taken in by the lens, is governed by the focal length of the lens: for example, a short focal length will give a wide angle or view. So you can photograph different parts of the view just by changing lenses–as shown in the three pictures on the right. The girl and the camera stay in the same position for each photograph, showing that subject and background enlarge equally as the angle of view narrows. Read the rest of this entry »
The lens illustrated is the type usually fitted to an SLR camera. It encompasses more or less the same view you see with one eye closed. The information on the front of the lens gives its focal length (50mm), maximum aperture (f2), maker’s name, brand name, and serial number. The side view shows scales for focusing, aperture setting and depth of field.
Modern lenses are made up from several glass elements ground to a precise shape and mounted inside a tube. Read the rest of this entry »
A focusing screen provides a flat surface on which an image can be precisely focused and allows the eye to see the whole image at once for framing and composing. It normally comprises a ground glass screen, a fresnel lens and one or more focusing aids.
A ground glass screen scatters light in all directions allowing the whole image to be seen, but the picture you see is brighter in the centre. Coarse etching of the glass reduces this. A fresnel lens comprises a series of stepped, concentric rings. Read the rest of this entry »
Most popular SLR cameras have a fixed focusing screen and pentaprism, both of which are more than adequate for day to day situations. Although both of these features make rapid focusing and composition easier, neither can be the perfect answer in every situation. For that reason many photographers choose an SLR with an interchangeable focusing screen, viewfinder, or both. You will find that some of the more expensive cameras have this facility. Read the rest of this entry »
Eye-level viewfinder cameras, with automatic focusing, are already available. The photographer simply points the camera at his subject and presses the shutter release. Camera-to-subject distance is measured in a similar manner to the rangefinder using the contrast between two superimposed images. When the two images are merged completely, contrast is at its highest, the lens is sharply focused and a special electric cell allows the shutter to fire. Read the rest of this entry »
Different types of cameras use different methods to focus their lenses, but with the common aim of providing the photographer with a sharp image on the film.
Focusing is either done by guessing or actually measuring the camera-to subject distance using a rangefinder. The lens is then set manually to the correct distance, or in some cameras the range finder is coupled to the focusing mechanism. In other focusing systems the image is seen through a ground-glass screen and the lens moved until the image is sharp. Read the rest of this entry »
Specific failure symptoms include: 1) The washer won’t complete the wash or spin cycle. 2) The washer has a burning smell during the wash and spin cycle. 3) The washer leaves water in the tub at the end of the cycle.
Check the washer power cord for a possible loose connection at the wall plug receptacle.
Check to see if the wall receptacle is defective or has burned or oxidized contacts. If so, the repair should be made by a licensed electrician. Read the rest of this entry »
Specific failure symptoms include: 1) Little or no water enters the washer. 2) The washer does I not complete the washing cycle. 3) The washer drive motor does not run during cycle. To find the cause of the problem, first check to be sure both the hot and cold water faucets are turned on at the wash station.
To avoid any incorrect readings when using the volt/ohmmeter, always “zero” the ohmmeter scale of the volt/ohmmeter before making any continuity checks on components. See operating instructions that came with the volt/ohmmeter. Read the rest of this entry »
