This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
61. A color-sensitive plate will do everything that an ordinary plate will do, so that the photographer who uses panchromatic plates exclusively is at no disadvantage as compared with the photographer who uses ordinary plates, but at a great advantage; for even without using any screen he may get some improvement in rendering, while with a screen his work will always be superior in this respect.
62. If the very color-sensitive panchromatic plate is used without a screen, it will give you about the same result as if you use the old orthochromatic plate with a four-times screen; consequently, whenever possible, you should use a screen.
63. Possibly you have used orthochromatic plates before, and have one or more screens. Naturally, you want to know whether you can save getting new screens by using those you already have. Examine them carefully, and you can easily ascertain this. If they consist of brownish-yellow glass, they are practically useless, will require great increase of exposure, and should not be employed. If they are light lemon-yellow they may be useful.
64. The four-times screen supplied by Burke & James, or the dry-plate and lens manufacturers, are suitable for general purposes for use with orthochromatic, trichromatic or panchromatic plates, and may be considered a standard all-around screen.
65. With a four-times screen on the regular orthochromatic plate you correct the blues, greens and light yellows with distinguishable results - that is, you bring all colors nearer their relative visual tone and produce contrasts, while with the same screen on a panchromatic or trichromatic plate you, in addition to the former corrections, correct the violet and red colors also, thus giving a true rendering of all colors in monochrome.
66. The color-screen should never be used on an ordinary plate, for it would require an enormously long exposure, and experience has taught us that it is of little value, over the ordinary exposing of the plate, without a screen; while with the orthochromatic plates, which are corrected for use with the screen, the exposure is but slightly increased over the ordinary plate without the screen. Thus it will be readily seen that the screen should only be used with orthochromatic plates.
67. For copying of colored objects, such as oil paintings, lithographs, etc., a fifteen-times screen will assist in producing better results, but for all ordinary purposes the four-times screen is recommended.