The most frequent application that an animated cartoon artist makes of a vignetter is making cross dissolves, or causing one picture to blend into another. Imagine now that the idea to be expressed, through the medium of one of these cross dissolves, is that of a character standing in an attitude of reflection and supposed to be thinking of how he would look in a complete suit of armor. There will be two drawings: one with the figure in ordinary dress, and the other with him clad in the armor. First the picture with ordinary dress is photographed. During this operation the vignetter is closed by degrees. When it is closed, the film that was just photographed upon is wound back again into the magazine. Now, as we know, during this procedure the light, which was getting weaker and weaker, proportionately lessened its effect on the sensitized emulsion of the film, so that its picture-forming property was not all used up. There is still a certain proportion of photographic potency left for the next exposure. The next step is to replace the first drawing with the one showing the character in armor.
VIGNETTER, OR IRIS DISSOLVE.
Below: Three stages during the movement of the pivoted segments.
We left the vignetter completely closed, and the same length of film that had just passed back of the lens has been wound back into the magazine and is ready to cross the exposure field again and be photographed upon the second time. Now the vignetter is gradually opened, the new picture is being taken and blended with the image of the first picture.
These two procedures in their method of operating and their effects compensate one another. The gradual closing of the vignetter has its reciprocal part in the gradual opening; the lessening of the light strength is reciprocal to the increase of the light strength; then the fading of definiteness in one picture is made up by the gradually increasing clearness in the other.
In trick work of this kind a mechanical counter would be very useful in measuring the length of film as it is turned into the magazine and then out again. It is understood, of course, that our particular counter also counts backward. And, again, with reference to cameras: an animator when he selects his camera should be certain that he gets one with which it is possible to turn the camera backward for making these dissolves and any other trick work involving like manipulation.
Immediately above we gave certain reasons for the making of tests on a small piece of film before photographing. Another matter for which tests should be made is the question of illumination. It is important that the field should be evenly illuminated. All this is an affair of adjusting the lights; that is, getting them one on each side of the camera in their proper positions with reference to the lens opening and the distance away from the drawing-board.
DIAGRAM TO EXPLAIN THE DISTRIBUTION OF LIGHT IN A CROSS DISSOLVE.