This section is from the "Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1917" book, by Aristo Motto. Also see Amazon: Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1917.
The form of distortion which comes from a failure to keep the plate in a perpendicular plane can be readily corrected in enlarging or in making prints the same size as the negative, using an enlarging camera. It is best to prevent the distortion by making proper use of the swing back when the negative is made, but this is not always done and sometimes is not practical.
In portraits made by studio and home portrait workers, one occasionally sees pictures in which there are straight lines that should be parallel, but failure to use the swing back in a proper manner has caused their distortion.
The distortion may be present whether there are straight lines or not, but straight lines of doorways, windows or furniture, encountered in working in the home, have made this distortion more often noticeable and its correction more desirable.
When a commercial photographer photographs a building from the street level he usually finds it necessary to raise his lens board and tilt his camera. He uses the swing back to keep his plate parallel with the building and stops his lens down to get the top as well as the bottom of the building in sharp focus.
The portrait photographer who uses a short focus lens deliberately throws his ground glass out of a perpendicular plane to prevent the distortion that would be noticeable when the hands and feet of a sitter are nearer the camera than the head and shoulders.
In such a case, straight lines in the background are sure to be distorted. This use of the swing back is unnecessary when a long focus lens is used, but this is not always possible in home portraiture. In photographing sitting figures, straight lines in the background should be avoided, or, if this is not possible, a side view of the body should be made so the feet and hands will be in the same plane as the head and shoulders. This permits the plate to be kept in a perpendicular plane, allows the lens to be used at a large aperture and avoids both the distortion of the straight lines and the figure.
The portrait worker has avoided straight lines for so long that he often becomes careless and produces distortion when it could just as well be avoided by straightening the swing back on his camera.
In such cases this can be corrected or improved by a reverse swing of the enlarging easel in making prints by projection instead of by contact. And since Artura Carbon Black is supplied in surfaces that correspond with those supplied in Artura Iris, prints made in this way are fully as satisfactory as contact prints.
If the camera swing-back is used to prevent distortion of a sitting figure, straight lines in the background will surely be distorted. And if the enlarging easel is swung away from a perpendicular line to correct the distorted lines, the prints will show distortion of the figure. An improvement can be made only by a partial correction or compromise.
But if the negative has been made with the plate tilted at an angle and unnecessary distortion produced, then it is a simple matter to entirely correct this by making prints by projection with the paper easel tilted.
The solid lines in our diagram show the camera with plate tilted, as is the case when perpendicular lines of the subject are distorted. Imagine the solid lines running from plate to subject are rigid wires. Also imagine that you can swing the back of the camera into a perpendicular plane and you can see that you would draw the subject into the position indicated by the dotted line which is the position for the easel to correct the distortion. Look at the diagram upside down for the opposite form of distortion and method of correcting same.
From An Artura Iris Print By Campbell Studio New York.
From An Artura Iris Print By Campbell Studio New York.
Diagram Showing Method of Correcting Distortion.
The distortion most often encountered is in photographs of buildings, but the careful commercial worker avoids this as a rule. It is in making enlargements or lantern slides for the trade that the worst cases are encountered and there is seldom a case in which a correction of this fault will not be welcomed by the owner of the negative. In fact, the writer knows of a case where the correction of distortion in making a few lantern slides secured an order for several hundred at a good price and made a permanent customer.
The distortion encountered in architectural work occurs when the camera is tilted upwards and the swing back is not straightened. To correct this in the print the top of the enlarging easel is tilted forward instead of backward, as shown by turning our diagram upside down.
These corrections are easily made on the New Model Easel which is made for use with the F. & S. 8 x 10 Revolving Back Enlarging Camera, but which may be used with any enlarging camera.
This easel has a locking device on the upright which allows the easel to be swung into a vertical position or tilted several degrees out of a plumb line to correct the forms of distortion mentioned above.
Once the easel has been set at the proper angle, it may be swung into a horizontal position for placing the paper. When turned back into position for making a print it automatically locks in position at the angle for which it has been adjusted, so that a dozen prints or enlargements may be made from a negative which shows distortion with but one adjustment of the easel.
If you have an enlarging camera - and if you haven't, you should add one to your equipment - select a negative in which there is distortion of straight lines and see how easy it is to correct it in a print. If your easel is not adjustable, have your dealer show you the New Model Easel.