. A new method for the measurement of photographic filter factors . Fig. 4.—Photographs taken with and without filters The exposure- limes with filters were adjusted according to the measured factors Measurement of Filter Factors 83 ment of about 69 cm, so that the range of factors which can bemeasured is from 1 to 30. The filters used must be larger thanone-half inch square. The strips of the photographic plate testedare \]4, by 5 inches, permitting two filter factors to be measuredconveniently on each. In measuring filter factors, four or five settings (one exposureat each setting) are made
. A new method for the measurement of photographic filter factors . Fig. 4.—Photographs taken with and without filters The exposure- limes with filters were adjusted according to the measured factors Measurement of Filter Factors 83 ment of about 69 cm, so that the range of factors which can bemeasured is from 1 to 30. The filters used must be larger thanone-half inch square. The strips of the photographic plate testedare \]4, by 5 inches, permitting two filter factors to be measuredconveniently on each. In measuring filter factors, four or five settings (one exposureat each setting) are made with each filter as described inSection II, 2. Since nine exposures can be made on each testplate, a single plate serves to test two filters. The trouble and loss of time required to make preliminarytests were avoided by preparing tables, such as Table 1, which givethe range of settings of the lamp suitable to the color sensitivityof the various types and brands of plates and filters. For example,filter Ki with a panchromatic plate was tested for the scale posi
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