198 NATURE-STUDY REVIEW [12:5— May, 1916 



If a short exposure is given when a ray filter is employed, the 

 resulting negative will be flat. 



The price of these filters varies from fifty cents to two dollars 

 depending upon the size and make. It is best to use the par- 

 ticular make of filter recommended by the manufacturers of 

 the particular plate used. 



Printing 



Any number of prints may be made from a negative after it 

 is once dried. It is placed in a printing frame with image-side 



Fig. 4. Desert. Near Seligman, Ariz. 

 August, 1915. Aperture F-32, time 4 seconds, ray filter, bright light. 



up, a sheet of printing paper is laid on so that its emulsion side 

 is in contact with the image-side of the negative, and the back of 

 the printing frame is clamped into place, holding the paper 

 firmly against the negative. 



Exposure is best made to an artificial light as sunlight is often 

 very variable The time of exposure will depend upon (a) the 

 intensity of the light, (b) the distance of the printing frame from 

 the light, (c) the thickness of the negative, and (d) the brand of 



