This section is from the "Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1911" book, by Aristo Motto. Also see Amazon: Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1911.
Do you make enlargements from your portrait negatives? If so, the following method of determining the correct exposure for any size enlargement will appeal to you. It is practical, not merely theoretical, but may only be applied to the making of enlargements by artificial light.
When you are printing the regular order of contact prints from the negative, note the time necessary for making an Artura Iris print with the negative at a given distance from the light. This last is most important as each succeeding test must be made with the negative at the same distance from the light. For example, we will say this Iris time is six seconds. Now make an Artura Carbon Black or Bromide enlargement 8 x 10, being sure to make tests to get the exposure absolutely correct. We will say you are using Bromide and the correct exposure is fifteen seconds. Divide the fifteen by the six and you have 2 1/2, which is the factor to use in determining the correct exposure for an 8 x 10 enlargement from any negative.
Suppose, for example, the correct exposure for the Iris print is ten seconds; the exposure for the 8 x 10 Bromide will be 2 1/2 times ten or twenty-five seconds.
You may now take any negative of the same size as the one used in the first test and when you know the correct exposure for an Iris print and multiply it by 2 1/2 you will have the correct time for an 8 x 10 Bromide enlargement. It is easy to see what an advantage this method is to the photographer who is making a specialty of a certain sized enlargement, but it may also be used to determine the exposure for any other sized enlargement. It is not necessary to find the factor for each size, as the result may be obtained without making the different sized test enlargements.
If a larger print is desired you have the exposure for the ten inch print; square the ten and you have 100. You want to make a 14 x 17 print; square the seventeen and you have 289; divide the 289 by 100 which gives 2.89, showing that the seventeen inch print has an area 2.89 times greater than the ten inch print. Hence if the proper time for the 8 x 10 enlargement is 25 seconds, the time for the 14 x 17 enlargement will be 2.89 times as long which is 72 1/4 seconds. The light decreases in intensity in proportion to the larger area which it covers, so the time for any size enlargement may be determined by having the correct exposure for a given size. In using this factor to determine the exposure it is understood that the lens of enlarging camera is stopped down to a given point and used at the same stop for all exposures.
The process of making enlargements of a given size may be made still more simple by having a set point for the enlarging easel and camera front where the full size of negative is to be enlarged, making the apparatus fixed focus. Of course where only a part of a negative is to be used, the regular method of focusing would have to be resorted to.
West Virginia Photographers' Association, Grafton, W. Va., October 10th, 11th; Secretary, Friend Cochrane, Charleston, W. Va.
Missouri Photographers' Association, Kansas City, Mo., Octo ber 3d, 4th, 5th; Secretary, L. S. Kucker, Springfield, Mo.
Photographers' Association of Illinois, Springfield, 111., October 17th, 18th, 19th, 20th; Secretary pro tern., Victor Georg, Jr., Springfield, 111.
In mounting prints a good heavy roller is a necessity. It saves time and insures the print being in contact with the card. These two rollers are both good ones. The Eastman No. 1 Double Print Roller has two eight inch rolls covered with first quality heavy white rubber and the solid heavily nickeled handle affords a strong, firm grip. The weight is a full five pounds. The Eastman Single Print Roller has a single ten inch roll, first quality heavy white rubber, weight same as the double roller, five pounds.
Eastman Single Print Roller .... $2.50
Eastman No. 1 Double Print Roller . . $3.00
Athletic Pictures are most interesting to the friends at home, and you will appreciate them highly when college days are over. Let us show you our new College Panels and other suitable styles.
Des Moines, Ia. ......Oct. 3, 4, 5
Louisville, Ky...........Oct. 10, 11, 12
Nashville, Tenn. ......... . Oct. 17, 18, 19
New Orleans, La.......... Oct. 24, 25, 26
Atlanta, Ga. .......... Oct. 31, Nov. 1, 2
Roanoke, Va............. Nov. 7, 8, 9
Baltimore, Md........... Nov. 14, 15, 16
By Gertrude Kasebier New York,N.Y.