CENCO NO. 87380

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## 3. SETTING UP THE APPARATUS

(1) Place the apparatus on a horizontal surface and orient the leveling screws G, located on the base, until they are directly beneath the fixed lenses A. A Cenco No. 85262-1 Optical Illuminator, or any projection lantern producing a parallel beam of light three inches or more in diameter, is suitable for use with the color apparatus. Place the light source within a few feet of the apparatus and adjust the beam of light until it passes through the fixed lenses and is parallel and coincident with the horizontal axis of the apparatus.

(2) Adjust the three light beams which emerge from the fixed lenses until they are sharply focused on the three closed diaphragms. These adjustments are critical and require careful manipulation of the light source.

(3) Place a projection screen approximately ten feet in front of the apparatus. A greater distance can be used for larger circles of projected light.

(4) Adjust the three diaphragms until the three light beams have equal intensities. Careful alignment of the light source with the axis of the apparatus will insure that each beam will receive an equal amount of light.

(5) Move the disk containing the circular openings forward and backward from the fixed lenses until a position is attained whereby the circles of light falling on the screen are sharp and of uniform intensities. If the light circles are tinted around the edges, adjust each individual diaphragm until a pure white light is obtained.

(6) The three adjustable lenses can be adjusted in relation to the center of the corresponding diaphragm openings to make the light circles overlap on the screen as desired.

## 4. OPERATION

**Primary and Secondary Colors:** Insert the red, green and blue filters into the slide holders and adjust the lenses so that the three circles of light coincide to produce a single circle of white light on the screen. If after the lenses have been adjusted, the projected light still contains a residual hue, adjust the diaphragms until the hue is eliminated. The resulting intensities of the white light and its various parts are the ratio of one, two and three. Next, separate the circles by adjusting the lenses to overlap as shown in Fig. 1. The various color shades obtained are the result of combining the primary colors in pairs to form secondary colors. This shading may be further enhanced by slowly closing the diaphragm of the red and then the blue, ultimately leaving only the green. All secondary colors from yellow through purple will be slowly formed. The same experiment can, of course be carried out by substituting other combinations of primary colors.

**False Primary Colors:** Substituting the purple, yellow and blue-green filters in place of the original primary colored filters, produces white and all of the secondary colors the same as with the real primaries (see Fig. 2).

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CENCO NO. 87380

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**Complementary Colors** may be arranged by the use of filters, as in Fig. 3, or by reference to the previous experiments just described. In Figs. 1 and 2 it is evident that one primary color is complementary to the color produced by the combination of the other two primaries.

An impressive demonstration may be performed by first superimposing the yellow and blue filters in a single holder of the apparatus, thus producing a green colored light beam. Then by inserting the same filters in separate holders and causing the beams to overlap on the screen, a white spot is obtained. The yellow is composed of primary colors red and green, therefore adding the third primary color, blue, results in a white spot being formed.

**Contrast Effects** are strikingly presented when a complementary color, such as green is projected first, then a white spot previously arranged to partially overlap, is projected. The overlap, which is really a tint, appears nearly white while the remaining white appears strongly tinted with the complementary color (see Fig. 4).

**Tints** may be obtained by first adjusting a colored beam for correct intensity, then superimposing it over a white beam.

The apparatus can be used to produce other interesting experiments in color. For instance, if three equally bright white beams are made to overlap partially as in Fig. 1, the various sections of the resulting figure will present intensities in the ratio of one, two and three. When the compound white is projected on the screen, and an opaque body is held in the path of the rays, a unique shadow will be produced.

## 5. MAINTENANCE

The six color filters supplied with the apparatus should not be exposed to strong light or heat for long periods of time, since excess heat and light will cause the filters to fade. Store the filters in a lightproof container when not in use. Keep the lenses of the apparatus clean and protect them from damage caused by mechanical shock.

## 6. REPLACEMENT PARTS

<table><thead><tr><td>Description</td><td>Cenco No.</td></tr></thead><tbody><tr><td>Red Filter</td><td>P67237</td></tr><tr><td>Green Filter</td><td>P67238</td></tr><tr><td>Blue Filter</td><td>P67239</td></tr><tr><td>Blue-Green Filter</td><td>P67240</td></tr><tr><td>Yellow Filter</td><td>P67241</td></tr><tr><td>Purple Filter</td><td>P67242</td></tr></tbody></table>

## 7. ACCESSORIES

<table><tr><td>Optical Illuminator</td><td>85262-1</td></tr><tr><td>Projection Screen, Class Beaded</td><td>56095</td></tr></table>

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