232 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



is usually troublesome in the rough-surfaced print, practically disap- 

 pears. There is also a great improvement in the rendering of shadow 

 detail. 



Oil paintings, ordinarily very diflBcult to photograph, become very 

 simple indeed. The reflections from the canvas texture, from varnish, 

 from age cracks, and from the pigments themselves disappear, so that 

 the picture is not obscured by rows of bright spots. We can now 

 record the painting instead of its surface. 



The efl'ect of tliis control on polished carved wood is remarkable. 

 If we go to the extreme, the grain is brought out in a remarkably 

 clear manner, and the gloss practically eliminated. Optically, we can 

 remove the varnish. If we go to the other extreme, that is, setting 

 the lens Pola-screen parallel to those at the lights, the polish is en- 

 hanced, and the grain subdued. The control in this du'ection is less 

 than that possible in subduing the reflections. 



If it is desired, the reflections from transparent wrappings may be 

 greatly subdued. The effect on lacquer is quite remarkable. Glossy 

 lacquer may be made to appear matte or its glossiness may be appar- 

 ently increased. 



Pola-scrcens should be particularly valuable to those engaged in 

 clinical photography. The reflections from wet surfaces of clinical 

 specimens frequently hide detail which it is desired to record. These 

 reflections may be subdued to any dcsu'ed extent to show up detail. 

 One of the effects of removing surface reflections is to show up very 

 strongly small differences in skin color. Slight skin discolorations, 

 incipient rashes, and so on, may be shown very well. 



We believe that there are a number of unexplored fields for the 

 Pola-screen, for instance, in unusual lightings and unusual background 

 effects. As one example — if we place a light directly in front of the 

 camera, tlie lens flare normaUy resulting degrades the contrast of the 

 picture. If Pola-screens are placed at the light and the lens, the 

 brightness of the light itself may be very greatly subdued with very 

 little effect on the illumination of the subject. 



A background of variable brightness is provided by the use of an 

 aluminized sheet (such as a cine or Kodascope screen), lighted by a 

 spotlight through a type II Pola-screen. The sheet is placed to throw 

 a bright reflection into the lens. Rotating a type I Pola-screen at the 

 lens varies the background brightness from very dark to very bright. 



Another effect of possible interest in motion picture title work in- 

 volves cellulose sheeting and transparent ceUulose tape. Wlien placed 

 between crossed Pola-screens, the sheeting can be made to appear 

 either light or dark, depending upon its angular position. Various 

 colors result from the use of varying thicknesses, so that patterns in 

 vivid color can be formed by multiple layers of the ceUulose material. 



