Lighting conditions indoors are much more uncertain than in the open air. The strength of the light as well as its direction may vary a great deal according to the size of the windows and the way they are facing. Besides, the room itself may be large or small and decorated in light or dark tones.
Exposure tables are almost useless. Only an exposure meter is of assistance in these conditions, and it must be sensitive to weak light.
The photographer, who would occasionally take a photographic record of some place, needs little to remember beyond the rules about camera position, focusing and choice of lens aperture which apply to all types of photography.
If your equipment allows, choose a lens of suitable focal length for the dimensions of the room. In confined conditions a wide-angle lens is very useful. If your camera has no interchangeable lenses, retire into the farthest corner of the room to cover the widest possible view.
Even when daylight is present, artificial light will almost always be required to bridge the contrasts and thus obtain a satisfactory color rendering. The type of illumination most suitable for the purpose will depend on the amount of daylight entering the room, and on the position of the windows relative to the camera.
Be careful to select the type of room for most interesting portion to photograph, since it’s virtually impossible to include an entire room in a single shot. As i already said lighting conditions indoors are much more uncertain than in the open air so the indoor lighting is important.
If the room is fairly strongly lit from outside, daylight type color film is called for.
First ascertain the lens aperture that will be required to give sufficient depth of field over the subject. Next measure the light reflected by the most brightly lit area close to the window.
Now take another meter reading on the shadow areas of the subject. If these areas reflect one sixth as much light (or more) as the highlights, you can set the camera shutter according to the reading obtained on the highlights. Then expose by daylight alone, as the brightness range of the subject lies within the range of the film.
But it is far more probable that the shadow areas will be many times darker than the highlights near the window. They can be lightened with blue flash bulbs or electronic flash.
Assume that the lens aperture required for adequate depth of field is f16, and the dark end of the room is 10 feet from the camera. With, for instance, a PF 60/97 flash bulb, the suggested guide number for a single bulb is 80 for film rated at 21° BSL This gives an aperture 80/10 = f8.
An aperture of f16 would require four times as much light, i.e. four bulbs. But as the daylight was not included in this calculation and the fill-in lighting should be somewhat subdued, the number of flash bulbs can be reduced to three.
The great advantage of electronic flash with static subjects is that it can be fired a number of times during the same exposure, from different positions if desired, and at a fraction of the cost of flash bulbs.
To illustrate its application to interiors, let us assume that you wish to make an exposure in a room measuring about 20 X 12 feet with a single window in one of the end walls, and that your lens will cover the scene adequately. Place the camera in one corner, at the window end and point it diagonally across the room. To supplement the light from the window fire successive flashes from various positions beside and in front of the camera. But before doing so you take a series of light readings with a reflected light meter on a white card held up at successive intervals of 3 feet from the camera position along the lens axis.
Typical readings for a film speed of 21° BSI may be half second at f4.5 at 3 feet, and 2 seconds between 9 and 12 feet.
At the latter distance the light is one quarter of that recorded at 3 feet. This is the limit of permissible contrast for correct color rendering.
Between 12 and 18 feet an average exposure reading may be 4 seconds at f4.5, which calls for auxiliary lighting.
Now place the camera in position on a tripod, focus and set the aperture to f16. The average exposure for the near zone between the camera and 9-12 feet away is 1 second at f4.5 or about 16 seconds at f16. This needs a correction for long exposure times giving 24 seconds at f16.
As you see, you cannot work this out in your head!
Now calculate the number of flashes required. With a 200-joule portable electronic flash outfit, the suggested guide number for a film rated at 21° BSI is 21 to 24. The flash is to be fired towards the ceiling from behind the camera, so as to light the scene indirectly. One flash at an average distance of 12 feet gives an aperture of 24/12=f2; or two flashes at f2.8; four at f4; eight at f5.6; sixteen at f8; thirty-two at f11; or sixty-four at f16.
The problem is how to combine the multiple flashes with the necessary 24 second exposure calculated for the daylight. The recharging rate of the flashgun will not permit the firing of 64 flashes in 24 seconds. It will therefore be necessary to give 96 successive exposures of half second, firing the flash gun during 64 of them. Of course the camera must be firmly supported throughout the proceedings.
However crazy the method just described may seem, it has given the author successful results on several occasions!
In the very unusual event of you’re wishing to use PF 60/97 flash bulbs you will need at least eight of them.
For interiors where there is no daylight involved and no persons or moving objects in the field of view, use either Photofloods with artificial light type film, or electronic flash with daylight film. Both methods call for prolonged exposure (either continuous or interrupted) as the Photofloods, though economical as compared with flash bulbs are relatively weak; and the electronic flash tube must be fired a number of times.
Appropriate flash bulbs could be used with a brief time or instantaneous exposure, but this is an uneconomic method with a static subject.
Let us start with the Photofloods and artificial light film. Place one Photoflood in position to provide the main lighting and use a second one as fill-in. While the camera shutter is open move this second Photoflood from side to side and up and down, but do not encroach on the field of view.
As conditions in such cases will vary greatly according to the size and decoration of the room, it is impossible to give detailed advice on exposure. A white card reading with a reflected light meter, or incident light measurement, to be taken in either case from the centre of the subject, can provide a basis for tests.
Whether or not the normal room lights should remain switched on throughout the exposure will depend on their position relative to the camera and their power. Unshaded lamps may cause a halo effect and internal reflections in the camera lens. The best solution to this problem can only be found by experiment.
If time exposures are called for, remember to apply the increase recommended by the manufacturer, and use the appropriate filter if required.
With electronic flash and a daylight type film you can proceed on similar lines as when using the flash to supplement daylight.
Assume that a 100-joule electronic flash unit is available. With a film rated at 22° BSI the suggested guide number is 20. If the tube is placed at 10 feet from the principal plane of the subject, a single flash would thus call for an aperture of A According to the aperture dictated by the depth of the subject, the number of successive flashes required will then be one at f2, two at f2.8, four at f4, eight at f5.6, and so on, up to sixty-four at f16.
Owing to the need to recharge the tube, flashes can only be fired at the rate of one every five to ten seconds. Therefore if a large number of flashes is required, and there is any light coming in from outside or from the normal room lights, it is advisable to keep the shutter open for only short periods at a time.
In this case expose for the exterior view and fill in the detail in the interior by means of blue-tinted flash bulbs. You need daylight type emulsion.
Any attempt to expose for the interior without the use of auxiliary lighting would result in the exterior view being completely burnt out owing to the excessive contrast.
First calculate the exposure for the exterior view. Assume that it is 1/10 second at f22 and that the interior view is to be lit up with PF 60/97 flash bulbs. To obtain an effect of full daylight inside the room, the number of synchronized PF 60/97 bulbs required to be fired at about 5 feet from the foreground view will be three bulbs at f22, or two bulbs at f18, or one bulb at about f13.
For a darker and possibly more natural rendering of the interior in relation to the exterior view seen through the window, the number of flash bulbs may be reduced to two at f22.
Estimate the exposure for the lamp or fire in the room, using an artificial light film. If the shadow areas appear, to require filling in, fire one or more clear bulbs during the exposure. In this case set the aperture according to the flash guide number which is about double that for blue bulbs.
Industrial photography is specialized work and calls for extensive equipment, such as cameras for different negative sizes and lenses of various focal lengths.
As working conditions are seldom known in advance it is necessary to have both daylight and artificial light emulsions ready to hand loaded in cassettes or dark slides, plus a set of filters.
The choice of film is dictated by the nature of the lighting. Natural and fluorescent lighting require a daylight emulsion and any auxiliary lighting must be balanced accordingly, e.g. blue flash bulbs and electronic flash.
With close shots of machinery (possibly also a man working in the foreground) weak general lighting may be left out of account. Powerful spots placed close to the subject will pick out the real parts of importance. Alternatively, use clear flash bulbs with a flash light emulsion.
Many difficulties stand in the way of successful general views in color. Large workshops have many machines which may be in motion. Operatives have to be persuaded to keep still. There may be strong lights facing the camera, especially in dull weather, when natural lighting bays are within the field of view; and there may be a mixture of daylight and artificial light. You will often need several flash bulbs, the fill-in bulbs being either connected to the gun by long leads or fired by photo-electric slave units.
Give at least double the exposure indicated by an incident light meter, as the machines are generally very dark.
Polarizing filters can be used with advantage for objects under glass, and of course for photographing shop window displays. The filter must however be correctly orientated (check on the focusing screen or by visual observation). Set up the camera so that the lens axis forms an angle of 30 to 40 degrees with the glass surface causing the unwanted reflection (At this angle the reflected light is polarized to the greatest extent). The filter means an increase of exposure of about 2.5 times.
Polarizing filters will not suppress reflections from metal.
Before taking a picture, examine the subject at leisure from different angles. Choose a camera position sufficiently far away to obviate distortion, unless of course you are after a special effect.
You cannot do much about the lighting when the subject is in a museum. But when sunlight, direct or filtered through cloud is available, or with artificial light, a fair measure of control is possible.
Bas-reliefs look best by oblique lighting. A variety of effects can be obtained by using a reflector, a flash bulb or electronic flash in daylight, or diffused fill-in lamps with spotlights.
With high reliefs and statues diffused artificial light is often better than a spotlight.
Take careful note of the background; it should preferably be neutral in color. If it appears unsuitable, but cannot be changed, it is best to leave it blurred by focusing accurately on the foreground and using a large aperture.
The difficulty with stained glass is to estimate the exact exposure for a true and well-saturated color rendering.
In the absence of a meter, correct exposure is a matter of trial and error.
An optical photometer presents a distinct advantage over photo-electric cell meters. When the window is high up or out of reach it is the only instrument with a sufficiently narrow acceptance angle to permit separate readings to be taken on different parts of the window without including the walls of the building in its field of view.
If you have a reflected light meter, hold it close to the window (or take a reading on a similarly lit window at a convenient height). Otherwise a large part of the dark wall may be included in the field of view, giving a false exposure reading.
If you are able to get near the window be sure to include several colors in the field of view of the meter, and not just a blue or red fragment.
To make a church window stand out against a very dark background (if the church itself is dimly lit) there should be no auxiliary lighting.
Sometimes you may want to include some details of architecture or sculpture on the supporting wall so as to obtain an impression of architectural unity.
This calls for a little calculation. Assume that the camera is placed at 20-25 feet from a window and the field of view includes sculpture and relief work on an important surface of the wall. The lens aperture is to be set at f8. The film is rated at 21° BSI.
Now if you wish to render the wall and sculpture in their original colors, i.e. give them the same prominence as the window, use one or more flash bulbs, as if the wall were the main subject Thus with a PF 60/97 the required aperture would be 80/20=f4.
Alternatively, if you want to obtain no more than an impression of the architectural detail emerging from the shadows, use half as many blue flash bulbs.
Note that in the present case an electronic flash unit cannot be used. The exposure time is too brief to permit a sufficient number of flashes being fired in the time available.
Few photographers are likely to get a chance of descending into underground caverns. Such places, however, sometimes present an amazing display of color, and are well worth recording on color film.
The lighting has to be self-contained, and flash bulbs and electronic flash are ideal. Used from the camera position, they record the scene as it appeared by the light of a single carbide lamp held in front of the observer. One can call this in a sense an “accurate” record of the view as seen at the time, but it suffers from the defects of being very flat and of conveying no real idea of the nature of the subject. Any transparent effect is of course also lost.
To get color photographs which give a true rendering of the spectacular scene, or even suggest it, a number of lights are required. They will have to be arranged in different positions, some facing the camera, and large open areas should preferably be lit from the side.
There is a wide choice of lighting as you can use successive flashes from a single electronic flash tube, or a number of flash bulbs placed in different positions. Combinations are also possible of tungsten lamps (when available) and flash bulbs, a carbide lamp and flash bulbs, or electronic flash and blue flash bulbs.
Normal flash guide numbers apply in this type of work, though you have to allow for unusually light or dark walls and nearby rock masses.
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