It is necessary in a dark room to see, not only the plate but objects in the room as well. A diffused light is much better for this purpose than a direct light, objects in the room being readily distinguished with less strain on the eyes. This principle is applied to the Wratten Safelight Lamp, all the illumination, coming through the safelight, being reflected light.

As a brighter safelight can be used with an ordinary plate than with a very rapid or an ortho-chromatic plate, it is obviously desirous to change the safelight as occasion demands, this being done instantly with the Wratten Safelight Lamps. Each of the Wratten Safelights has been designed in conformity with Dr. Mees' standard, allowing a good margin of safety for the work for which they are recommended.

The illustration following the description of each safelight shows at the top, a photograph of the spectrum made on the plate with which the safelight is to be used showing that part of the spectrum to which the plate is sensitive, and below another photograph of the spectrum on a Wratten Panchromatic plate with the safe-light placed in front of it, showing the color of light which passes through the safelight.

As the Wratten Panchromatic plate is sensitive to all the colors of the spectrum, the lower illustration shows conclusively that the light which passes through the safelight is not of a color that will affect the plate with which the upper photograph was made.

Series 0 Safelight. A bright orange color suitable for use with Bromide paper and Lantern Plates. Fig. 5 shows the results of the spectrum photographs mentioned above.

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Fig. 5

Series 1 Safe light. An orange safelight for use with ordinary, medium and extra rapid plates which are not color sensitive. Fig. 6 shows the results of the spectrum photographs.

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Fig. 6

Series 2 Safelight. A red safe-light for extra rapid and ortho-chromatic plates which are sensitive to green but not to red. Fig. 7 shows the results of the spectrum photographs.

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Fig. 7

Series 3 Safelight. This is a green safelight for use with the red-sensitive Panchromatic Plate. It gives a very faint illumination which appears to be quite strong as the eyes become accustomed to it. Fig. 8 shows the results of the spectrum photographs.

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Fig. 8

The upper illustration shows the result of an exposure to the spectrum of less than one second on a Wratten Panchromatic Plate. The lower illustration shows the result of an exposure of over two hours on the same plate with a No. 3 Safelight in front of it, the light used being a 10 ampere arc lamp.

These safelights are made for the Wratten Safelight Lamps but may be used with any lamp that is light-tight and well ventilated. The Series 2 is the most generally used as it is safe for any plate except a panchromatic. The Series 4, a green safelight, may be used with ordinary plates by those who cannot use a red light. It is not safe for Ortho-chromatic Plates unless used with extreme care.

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FROM AN ARTURA IRIS PRINT

By Edward II. Weston Tropico, Cal.

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FROM AN ARTURA IRIS PRINT

By Edward H. Weston Tropico, Cal.

Wratten Safelights are made by coating glass with stained gelatine, the dyes used being spectroscopically tested to make sure that they absorb the necessary colors and transmit as much as possible of the light of safe color. At the same time they must be permanent to light so they will not fade.

The Wratten Safelights are regularly furnished in three sizes at the following prices:

(ANY SERIES)

5 x7.......... $ .60

8 x 10.......... 1.20

12 x 15.......... 2.25

A modified form of the Standard Wratten Safelight Lamp is described on page 27.