US1784171A - Artificial lighting having a daylight effect - Google Patents

Description

Dec. 9, 1930. H. BERTLING ARTIFICIAL LIGHTING HAVING A DAYLIGHT EFFECT Filed April 28, 1928 jf, WW

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Patented Dee. 9, 1930` HERBERT BERTLING, OF BEBLIN-WILIEBSDOBF,

ARTIFICIAL LIGHTING HAVING A DAYLIGHT EFFECT Application led April 28, 1928, Serial No. 273,731, and in Germany Hay 14, 1927.

The present invention has for its object to produce an ortho-actinic light for photography having the correct color brightness in monochrome photography and producing correct colors in polychrome photography.

The case is different in photography and kinematography, The light of mercury vapour lamps and arc lamps using carbons for obtaining a special effect usually employed in this connection is very rich in blue and violet rays, while green is very Weak, yellow very weak and red is much weaker. Bromide of silver, however, is most sensitive to blue and violet rays, far less sensitive to yellow and green and almost entirely non-,sen-

sitive to red rays. Consequently the colours cannot appear in their correct values as regards luminosity, blue and violet predominating. Even when using a sensitized surface which has been made specially sensitive to green, yellow and red (panchromatic layers) it is impossible to obtain the correct colour values when employing the usual illumination, as the necessary green, yellow and red rays are lacking, or are not present -in sufficient quantities. The conditions are similar, when taking colour films, colour photographs and the like.

Efforts have been made for a long time to give the mercury vapour lamp a light similar to that of daylight by the addition of metals or other substances the maximum light emission of which lies in the red part of the spectrum (for instance potassium, zinc) but such eiflorts as Well have not led to the desired resu t.

The method of the artificial illumination of objects according to the present invention consists in this, that light producing devices arel used, in which rays of different coloured sources of light are mixed and the object is illuminated by means of combinations of separate lamps. .The combination of lamps is so arranged that by associating lamps, the d character of the emitted rays of which differ, the combination results in a continuous or approximately continuous spectrum. The intensity or quantity of the separate kinds of rays is regulated by increasing the number or size, or by decreasing the number or size of the lamps deliverin these kinds of rays. The composition of t e li ht obtained by means of the combination 0% lamps can thus be regulated or adapted to the particular ob- ]ect in view. Thus, for instance, the intensity or quantity of the separate kinds of rays of light can be adjusted to the sensitiveness of the sensitized surface, so that, for instance, when the sensitized surface is very sensitive to blue or not very sensitive to red, the number of blue rays in lthe source of light is correspondingly reduced and the number of red rays correspondin ly increased.

When, for instance, t e sensitiveness to blue, green and red of the sensitive layer is in G5 the proportion of 3 1 2, the quantitative radiation of the source of light is adjusted to the inverse proportion, that is, with the result that as compared with blue three times as much green and 1.5 times as much red will act on the sensitized surface.

The'procedure is similar in taking colour photographs, in the hotographic manufacture of colour print locks in three or more colours for making reproductions, and in all cases which require a particularquantitative composition of li ht. When, for instance, a colour photograp is to be taken according to .the subtractive method and the times of exposure through blue, green and red filters so are as 1:2:1.5 the source of light is so adjusted that twice as many green, and one and a half times as many red rays as blue rays will be emitted.l By this means the time of illumination for all three exposures becomes the same, which is of special importance when exposing films for the production of coloured projection pictures, as, when exposing such films, it is usual to use one lens only and a single stop or only one relative lens aperture for all three or two images taken through the filters.

Vhat has been said above with respect to correct values in the panchromatic film when exposures are made with a spectroscopicaflly incorrectly combined illumination, applies of course with equal force to 'the making of photographic exposures through filters and other methods of producing colour films. Thus, for instance, it is not possible to prothe sensitized surface is never uniform for the various kinds of rays of light, While the time of exposure for red, green and blue 1mages is practically always the same. This results in one image being correctly exposed while kthe other two are over or underexposed. When placing the separate colour images together to form a three colour 1mage, whatever the method adopted, the result will be that one colour will predominate, while the other colour will be insufficiently represented, which may be compensated for to some extent b dyeing more` weakly or more intensively, but incorrectness in colour will still remain.

In the case of two and four colour photography the conditions are the same.

According to the new illuminating method these faults are overcome.

The new method also makes it possible to take photographs which are correct in colour with a relatively small amount'of light, as the light is composed in accordance with requirements and the excess of certain rays is not, as hitherto, absorbed by filtration, which involved a great expenditure in li ht in order to have a certain kind of rays available. The new method of illumination has the further advantage, that it has no physiological effect, so that for instance when films are being taken the actors will no longer be inconvenienced and suffer in health through the excess of blue light. The colour of the light in the combinations referred to above by way of example is, on the contrary, extremely pleasing and warmer than daylight.

The apparatus for producing this source of light consists in this, that separate sources of light having a specific emission of blue, green, and red rays in adjusted proportion are united and together give the required light emission. Suitably theseparatc sources of light are mounted in boxes or frames, mixed in'thel required ratio as regards thc composition of the light.

Different kinds of lamps may he used as sources of light, provided that they are capable of eimtting one or more kndsof rays and that any lack in one kind of ray may be. compensated for by an additional source ofi light having another spectrum.

e accompanying drawing shows diagrammatically by way of example the application of tubular, electric, metal vapor or gas filled lamps.

Figure 1 is a front elevation of a lamp box containing a series of lam s arranged 1n accordance with the method) according to the invention.

Figure 2 shows the lamp box in horizontal section.

Figure 3 shows a modified construction of lamp box in horizontal section.

Figure 4 shows another modification of the lamp box in horizontalsection.

Figure 5 shows a device for swinging the lamps into position simultaneously.

For producing'the violet or blue rays a mercury vapour lamp I (Fig. 1) is used, which is preferabl in the form vof a mercury vapour lamp or the usual supply voltage, as such a lam gives a more intensive light than high vo tage luminescent lamps and is easier to manipulate.

The green rays are also produced by mercury vapour arc lamps II in front of which a yellow filter a is placed Which absorbs the blue and violet rays and allows the green rays to pass.

For producing the red rays, metal vapor lamps with metal emitting red rays, for example, potassium, are used, it being immaterial whether these lamps are operated with high voltage as luminescent lamps or with the usual supply voltage as arc lamps.

It has been found that the well known luminescent tubes with a filling of rare gas (more particularly neon for red) are very suitable. l

The filters' a are exchangeable for filters of different absorptive capacity, for enabling the light conditions to be accurately adjusted. For the same reason filter holders b are provided for the other tubes. In front ofthe whole set of lamps a round glass or milk glass plate can be lace for obtaining a very diffused light, if t is should be required. Instead of a single plate of ground glass being placed in front of the whole range of lamps, a separate piece may be placed in front of each lamp, for instance by being inserted in the filter holders b. The filters themselves may be made of ground glass or the like. In order to save light, the ground glass plates may he suitably replaced by plates of glass ground or pressed in patterns, which distribute the light effectively without much loss. The roar Wall of the box is preferably made. in the form of refiectorsd, (l.

Fig. 3 shows another consti'uctional form. Into the lamp boxes e, c `which are open at the back the lamp holders f, f are inserted with the lamps. At the front of thel lamp boxes (1,@ rectangular lenses g, g are provided which act as condensers giving the rays, according to the position of the lamps relative to the focus of the lenses, a definite angle of diffusion or a parallel direction. The lamps are shifted'by sliding their holders.

In Fig. 4 a'modification of the lamp box shown in Fig. 3 is illustrated. In order to be able to concentrate the rays on a single obing points 7c to the rear wall of each separate y lamp box. By means of the threaded spindle Z which is turned by means of a crank m, one member of the tongs may be opened or closed, thus causing the other members to be extended or contracted. As the separate lamp boxes are fixed at the points lo, they will be pivoted round the hinges 7L, h.

All the lamps can be removed separately, so that 'for instance in the same box a small lamp may be exchanged for a larger one or a green for a red one and so on, for varying the composition of the light in accordance with the requirements in each particular case.

The constructions described are only examples for illustrating the basic features of an arrangement according to the present invention, but do not exhaust all the possibilities as regards arrangement or shape.

What I claim is:

1. A device for artificially -illuminating objects for reproducing their daylight colour effect, for photography in correct colour values, forcolour photography and the like, comprising in combination a metal Vapour lamp emitting violet and blue rays, a second metal vapour lamp emitting violet and blue rays and having a yellow filter placed in front of it so as to pass green rays, a metal vapour ylamp emitting yellow and red rays, and

means for combining the rays of differently coloured light emitted from the respective lamps as set forth. Y

2, A method of producing correct color brightness values in monochrome photography and correct colors in color photography by the use of combinations of different colored sources of light, which consists in ad- ]ustlng the intensity of the individual spectral categories of light rays contained in combination, in accordance with the sensi#a tiveness of the sensitized photographic material to emit a definite category of light rays of greater intensity the less sensitive the photographic sensitized layer is to the category of light rays.

3. A method of producing correct color and adjusting the mission of these rays to suit the sensitiveness of the photographic material tothe individual rays in a manner that the emission of a definite category of light rays is made of greater intensity the less sensitive the photographic sensitized layer is to this category of light rays.

4. A device for artificially illuminating objects for photography in correct color values, for color photography and the like, comprising in combination a lamp emitting violet and blue rays, a second lamp emitting violet, green and blue rays, and having a filter placed in front of it, so as to pass green rays, a lamp emitting red rays, and means for combining the rays of differently colored light emitted from the respective lamps, as set forth.

5. A device for artificially illuminating objects for photography in correct color values, for color photography and the like, comprising in combination a metal vapor lamp emitting violet and blue rays, a second metal vapor lamp emitting violet; green and blue rays and having a filter placed in front of it s o as to pass green rays, a neon lamp` emitting red rays, and means for combining the rays of differently colored light emitted from the respective lamps, as set forth.

In testimony whereof I have signed my name to this specification.

' HERBERT BERTLING.

brightness valu-es in monochrome photography and correct colors in color photography by the use of combinations of different colored sources of light, wherein the combined course of light consists of separate sources .l

of light emitting blue, green and red rays

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