Wednesday, June 4, 2008

Practicus In the Studio: Artificial Lighting.

           It seems only a few years ago that a photograph taken by artificial light was somewhat of a curiosity and, with one or two brilliant exceptions, photographers were apt to regard it as a poor substitute for daylight, and, to tell the truth, the work generally produced quite justified their opinion. That I need hardly say was a time when electric mains were unknown, and the photographer who wanted to use the electric light had to install an engine and dynamo in his cellar or else to burn “white fire” in a specially built lantern, the precursor of the modern flashlight. The platen were then much dower than modern ones and the candle-power of the light much less, so that there was a tendency to reduce diffusion to a minimum, and chalky faces and black shadows were the usual thing. I mention these old times because there are still many people who imagine that there must be something inherently different between daylight negative and an artificially lighted one, and that the latter needs some sort of apology. This is quite a mistaken idea, and anyone who holds it should make tip his mind so to improve his work that even an expert should not be able to tell the difference.
           Before dealing with any of the types of installation which are now on the market, I should like to impress upon my readers that there is no essential difference between day and stifled lighting as far as effect is concerned – that is to say, that a top-light will give sunken eyes and hollow cheeks, a low side light will give the contrary effect, that an unscreened light gives the effect of direct sunshine, and that a well-diffused electric light gives much the same effect an ordinary daylight. This gives the key to successful lighting, for if the operator will carefully note the position of his dominant light when using daylight he can produce practically the tame effects with any other illuminant if he places it in the same position with relation to the sitter.
           The most important problem is that of diffusion, or one might say distribution, of the light, and the difficulty is greater or less as the original source of light is small or large; a single pair arc is the most difficult to manage and a battery of half-watts or small enclosed arcs is the easiest. Still the single large enclosed arc is not to be despised: I never feel unhappy with one at my command, therefore I will start my detailed instructions with this instrument.
           The enclosed arc is an ordinary single pair of carbons enclosed in a glass cylinder so as to be practically airtight. The effect of this is that a much longer arc can be maintained. A long arc emits more violet rays than a short one, consequently shorter exposures can be given. Incidentally there is leas consumption of the carbons, so that the lamp does not require much attention. An ordinary street lighting arc enclosed in a ventilated globe n classed as an open arc and must not be confuted with the enclosed arc properly o called. The difference between the various types of enclosed arc lamps is in the feed mechanism only and not in the light: with a given diameter of carbons and quantity of current you will obtain the came amount of light if your cylinders are kept clean. I hare worked continuously with the Westminster, Jandus, and Aristo lamps, and have found them all satisfactory. I think I have tried every reflecting and diffusing device on the market, and have come to the conclusion that the simpler the arrangement the better. My shade or diffuser - call it what you will - is made of two wooden hoops about 36 ins. across connected by four laths about 46 ins. long. Round these are bent thin cardboards so as to make a cylinder open at top and bottom with one-third left open. The inside of the card is covered with dead white paper (if white cards are used this is not necessary) and the outside with dark paper or cloth. The open third is now covered with tracing cloth, and the whole attached by cords to the chain or shackle from which the lamp hangs. It is a good plan to fasten the tracing cloth with push-pins so that it can be easily removed when the carbons have to be renewed or the glass cylinder cleaned. If possible the lamp and shade should be adjustable for height, so that it may be lowered for sitting figures and for children, it being always remembered that a foot or 18 ins. difference in position may mean 20 to 40 per cent difference in exposure. With this shade I have found no other accessories necessary, beyond an ordinary round screen, which I nearly always interpose about halfway between light and sitter, leaving the lower part of the figure unshaded, and the usual white reflector. I have sometimes hung a dark curtain or vallance to the edge of the lamp-shade to avoid a glare into the lens, but this is not always necessary.
           Open arc lamps are usually so fitted that only reflected light is used, the best known type, Marions Northlight, bane very similar to the original Van der Weyde model, but fitted with several pain of carbons to reduce exposure. The arcs are screened by a metal reflector on the sitter's side and the light reflected from the [whitened inside of an umbrella about 4*(1/2) ft. in diameter. The surface of this may be regarded as a brightly lighted window, and any necessary diffusion provided for with the head screen already mentioned; the reflector is, of course employed as needed. The highest type of work has been done with this system of lighting, the only drawbacks being a larger consumption of carbons and current than is necessary with the enclosed arc, while the large umbrella reflector takes up a good deal of apace in a small studio.
           Although there have been several other systems of arc lighting before the photographic public, the foregoing are practically the only survivors, and they will have a hard struggle for existence against the nitrogen-filled or "half-watt" lamps which are making rapid headway as the simplest and least expensive of any system which has yet presented itself.
           Before proceeding to these I should like to touch upon another form of electric lighting which has many good points: the mercury-vapour lamp. This is easy to manage, requiring no attention, and is economical of current, while owing to the large area over which the light is spread the lighting is fairly soft. Its one defect w it colour, which is greenish, and this gives anyone exposed to its rays a somewhat ghastly appearance. This can be overcome and the lighting improved by hanging a thin pink curtain in front of the tubes; this not only tones down the green but acts as a diffuser. As the tubes are somewhat long the lower part of the light tends to flatten the features somewhat, and I have found it advantageous to have the upright support lengthened, so that the bottom of the tubes are 4*(1/2) to 5 ft. from the floor. The tubes are rather fragile, so that care must be exercised in moving the apparatus about. Especial note must be taken of the connections so that the polarity is never reversed, or disaster will follow. It is easy to make such a mistake if a wall-plug is used, and some means should be taken to make it impossible to put the plug in the wrong way.
           The half-watt lamp as made for photographic work closely resembles the ordinary metallic filament lamps used for domestic lighting, but is much larger than these usually are. Its distinctive feature is that instead of the interior being as nearly a vacuum as it is possible to get, it is filled with an inert gas such as nitrogen, which, greatly retards the volatilization of the filament when the lamp is run at a high voltage. Most people know that if a lamp be run at an appreciably higher voltage than lit is made for the light is rendered much more brilliant, but that the life of .the lamp is shortened to a few hours or even a few minutes. Owing to their construction the half-watt lamps have practically the same life as the ordinary type, while the light is rendered white enough to enable short exposures to be made in the studio. The General Electric Company has devoted considerable attention to the photographic aspect of half-watt lighting, and send out not only suitable bulbs, but reflectors and stands ready for studio use. I have worked with several installations of half-watt lamps, and can recommend them to any photographer requiring a new installation. The lamps are made in various candle-powers from 500 to 3,000. I prefer the 1,000 c.p. as the best unit. If six 1,000 c.p. lamps be taken as the maximum power needed for ordinary work, these can be so spread out as to cover a considerable area and to give sufficient softness with very little loss of light by diffusion. If two 3,000 c.p. lamps were installed they would be as powerful as two arcs, and would have to toe placed farther from the sitter and a thicker diffuser would be needed. The metal reflectors supplied by the company are convenient and a great protection to the lamp, but I have found the light rather too concentrated, and have always fixed a thin white nainsook curtain in front of them. They can be fitted with a counterbalance weight like a grocer's scales, so that they may be raised or lowered to any desired height. A cheap method of fitting is to make large D-shaped reflectors of white card with a front of nainsook. The most useful size is about two feet wide by thirty inches high for the nainsook front, and eighteen inches deep from the centre of front to the back. One must be careful to place the lamp well in the centre, as there is a considerable amount of heat from the lamp, and if too near either lamp or calico one or the other will be burned. Light weight tinplate can, of course, be substituted for -the card for a permanent installation. I used the card lanterns for six months, and got one slight scorch only.
           With regard to the arrangement of the lamps it is difficult to give precise instructions, and in accordance with my previous remark I recommend them to be placed so as to allow the light to fall upon the sitter at the same angle that daylight usually does. As it is undesirable to place them between the daylight and the sitter they should be placed on the dark side of the roof in the same position as the open portion of the light. If it be desired to light the same side of the face as with daylight the lamps should be placed towards the other end of the studio and the camera turned round. For average lighting the lamps should be fixed so as to rise to eight feet from the floor for standing figures .and groups, and lower to about five feet six inches for sitting figures and children. The general arrangement may be in the form of a curve or L shape, one lamp being apposite the centre of the background and about seven feet away, another apposite the edge of the background and a little nearer to it, while two of the others are placed between these and two to serve as a side-light or for Rembrandt effects. Each lamp should be on a separate switch, so that only as many as may be necessary are burning at one time. It is very necessary that the exact voltage, not a nominal one, should be given when ordering lamps. Inquiry should be made at the local power station, for a very slight drop in voltage means but little loes of light visually, bat a gnat deal as regards the actinic value. In meet cases where length of exposure has been complained of I have found this to be die cause. In districts where variations of current are common it would be well to use slightly lower voltage lamps than the nominal local voltage calls for, and to have the adjustable resistance supplied for these lamps and regulate the current as needed.


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