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RECREATION. 



LENGTHS OF EXPOSURE. 

 I own a 4 x 5 Century Grand camera, 

 which is fitted with a convertible lens, the 

 different foci being 6 l /\. inches, ioYz inches, 

 and 14^2 inches. The longest focus re- 

 quires a considerably longer exposure than 

 the shorter ones. Can you tell me what the 

 comparative lengths of exposure should be 

 with the different foci, under the same con- 

 ditions, to produce the same result? Also 

 what causes this difference? Then, is it 

 not true that the wider the angle the lens 

 has the quicker it will wprk? 



E. W. Edgington, Le Mars, Iowa. 



ANSWER. 



It is only natural that the single elements 

 of a convertible lens should require longer 

 exposure than when the lens is used as a 

 compound. 



Supposing that the working aperture re- 

 mains constant with the use of the different 

 focus lenses,' and assuming that the 6^4-inch 

 focus lens should require, on a certain sub- 

 ject, an exposure of one second, then the 

 io^-inch focus lens would require 3 3-10 

 seconds and the 14^2-inch focus 46-10 sec- 

 onds. 



As the approximate speed of any photo- 

 graphic lens is secured by dividing the 

 equivalent focus by the opening of the 

 aperture, it will be seen that with a lens 

 which has an opening of one second and 

 an equivalent focus of 8 inches, the speed 

 value would be F8. If the focal length is 

 increased to 16 inches, retaining the same 

 opening of the diaphragm, which would "be 

 1 inch, the speed of the lens would then be 

 F16; so that, in this instance, should the 8- 

 inch focus lens require one secOnd exposure 

 the 16-inch focus lens would require 4 sec- 

 onds exposure. — Editor. 



A FISH ASSISTANT. 



Last summer I punched some holes in 

 a wooden box, hinged a cover on it and 

 tied it to the dock in front of my cottage. 

 I put about 20 velox and Dekko prints in 

 it at 11 o'clock one night, and expected 

 the motion of the waves to wash them by 

 morning. In the morning I tested them 

 with a 2 M N 208 and found plenty of hypo 

 left. It took a half hour of constant wash- 

 ing to get them test proof. 



The next night I had the same number 

 of prints to wash and as, I had a 2 pound 

 bass in the live box I put him in with the 

 prints. In the morning by the most careful 

 test there was no trace of hypo. The bass 

 washed all my prints after that and made 

 that part, usually the most tedious, the 

 easiest of all. He received a few big fat 

 minnows every day, and was given his 

 liberty the day I left the lake. This is no 

 fish story, but is true, and will be of great 

 benefit to all photo folk if they will try it. 

 I have no patent on it and it is free to all. 



The explanation lies in the fact that the 

 fish waved his tail and fins enough to sepa- 

 rate the prints, which the ordinary motion 

 of the box would not do. The box was 

 about twice as large as a starch box, or a 

 little larger than half a soap box. 



T. W. Harrington, Chicago, 111. 



I never miss a copy of Recreation. I 

 am an amateur photographer and thank 

 Recreation for many valuable suggestions. 

 I should like to know if the reproductions 

 of exposures in colors is a secret, or can 

 you give the process of sensitizing plates, 

 films or paper to give the proper color in a 

 photograph true to nature? Or, can you 

 tell me the address of some reliable firm 

 who make or handle such? Would prefer 

 to know the process. 



V. J. Levy, Spokane, Wash. 



ANSWER. 



A method for obtaining true colors in 

 photographs by sensitizing the plate or 

 paper has not yet been devised. Colored 

 prints are made, however, by the 3 color 

 process. This is done by making 3 nega- 

 tives of the subject, using different colored 

 screens and then printing from each nega- 

 tive on the same print in different colors. — 

 Editor. 



Will you kindly let me know whether or 

 not enlarging can be done with artificial 

 light ? Must I have a room arranged spe- 

 cially for that purpose ; or can it be done in 

 any room. What size would a 5 x 7 print 

 make? Will some experienced reader en- 

 lighten me as to making of enlargements? 



What is the best formula for the making 

 of good Velox prints? 



R. E. Godfrey, Jackman, B. C, Can. 



ANSWER. 



Enlargements are made by both daylight 

 and artificial light. A room that can be 

 made perfectly dark is necessary. 



Five by 7 prints can be enlarged to any 

 size you wish. 



The formula published by the manufac- 

 turers is generally the best one for their 

 products. Every package of Velox con- 

 tains such formulae. — Editor. 



Mother — Harold, darling, where is my 

 string of pearls? 



Harold — You mean the million-dollar 

 ones, mamma? I lent them to the poor 

 little girl next door to skip rope with. — 

 Collier's. 



Up-to-date Pastor — The collection will 

 now be taken, and those who contribute 10 

 cents or more will receive trading stamps 

 from the ushers. — Woman's Home Compan- 

 ion. 



