This section is from the "Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1919" book, by Aristo Motto. Also see Amazon: Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1919.
Daylight is best for copying paintings, but if artificial light is used a lamp should be used on each side to give even illumination and these should be so arranged that there are no reflections. Due regard must be given to the color of artificial light when selecting a filter. Artificial lights are generally deficient in blue while the plate or film has an excess of sensitiveness to blue. Naturally then as filters for or-thochromatic correction cut out more or less of the excess of blue light the correction need not be so great when an artificial light is used which emits only a fraction of the blue that is present in daylight.
The position of the camera is of great importance. The lens should be exactly in the center of the picture so that a line drawn through its axis would pass through the center of the picture and the center of the plate, otherwise the perspective will be objectionable. The plate must always be parallel with the picture and this without the use of the swing back. A lens must be used that does not distort and the flatter its field the better.
Pictures that contain a complete range of color necessitate the use of a panchromatic plate. The Wratten Panchromatic is sensitive to all colors. The difference between an orthochro-matic and a panchromatic plate is that while the former is fairly correct in its rendering of certain subjects, when used with a suitable screen, it is still much too sensitive to blues and is not at all sensitive to reds.
At first sight there may seem to be no prominent reds or blues in a picture, but they may be there as component parts of the colors you do see. In such a case you may not be able to detect a difference in a panchromatic and an orthochromatic result in the negative, but when prints from the two negatives are placed side by side you see it. There is a softness of gradation in the print from the panchromatic negative and a hardness and brokenness of masses in the print from the orthochromatic negative that makes all the difference between a good and a bad reproduction.
The Wratten K 3 Filter is undoubtedly the most generally useful as it reproduces truthfully in monochrome the relative brightness of the colors photographed. Often a K 2 Filter gives sufficient correction. On the other hand, the deep yellow G is sometimes preferable and in a few cases the red A for reproducing dark old oil paintings which generally contain deep browns and reds in which it is desirable to show rather more detail than is obvious to the eye at the first glance. It might be added that in using filters cemented in glass it is necessary to focus with the filter in position as it is only when the object is at a great distance that the difference in focus is inappreciable.
Eastman Portrait Film Negative, Artura Print By Frank W. Schaldenbrand Detroit, Mich.
There is nothing peculiar in the development of the panchromatic plate. One must remember that the object is to reproduce an effect in black and white that parallels the effect in color and unless this is done, no matter how good the result, it is a failure. As a general rule under-develop rather than over-develop as complete gradation must be secured in the print. Longer or shorter development will decide the contrast, assuming, of course, that the exposure has been correct. Full details of the working of panchromatic plates and the use of filters are given in the booklet,"Color Plates and Filters for Commercial Photography," and developing instructions will be found in each box of plates.
To successfully photograph paintings one must go to some extra trouble at first, but the necessary precautions soon become second nature and satisfac-factory results are easily secured. It needs but the comparison between an ordinary and a panchromatic plate result to at once appreciate the wonderful advantages of color sensitiveness.