an object, and therefore the object itself: 
full, 6.) cosi... do (see KASTEN, 
a, Turm r ru RASCHKE /3/; 
R = KRIEBEL /5/) 
L / cos. do 
w r N 
Ur 
  
Herein L. is the reflected radiance of an object as a function of 
zenith ahgle 4^ and azimuth $, integrated over a solid angle &. L,, denotes 
the (100 %) reflected radiance of a LAMBERT - Reflector. Therefore a 
reflection standard of this type has an importance, which exceeds the 
specific application of light fall - off compensation discussed here. 
Generally reflection standards do cover only a small portion of the 
camera's field of view; nevertheless it is possible to determine light 
fall - off corrections (see SIEVERS /6/). A more rigorous procedure 
requires standards which fill the camera's field of view totally. For the 
used camera / lens - configuration * a 120 cm diameter standard was 
requested. This is a size where the Bariumsulfat - substance may not 
layed on by a spattle and polished accurately, as done for small - size 
plates. 
Many approaches were made in order to find suitable material for the 
plate and appropriate methods for application of the substance. Because 
of the large size, a metal plate can not be used. Glass plates have to be 
roughened by sand blast and stabilized before putting Bariumsulfat on it. 
Application of the substance was tried first by a machine, which rotates 
the plane horizontally, generally used for putting emulsion on photo- 
graphic film ("KLIMSCH - ROTOR"). Caused by the rotation, bubbles of ca. 
0,05 mm diameter appeared, and the dry layer was entirely covered by 
tiny "craters". Also pouring the substance onto the plate without rota- 
tion did not lead to suitable results, because the layer cracked. 
Finally, excellent results were obtained by using a roughened, 
120 x 120 x 1,2 cm PVC - covered wooden plate and application of liquid 
btai Ba SO, - substance by a spray gun, observing the general instructions 
btained for varnishing. The spray effect leads to the desired degree of roughness, 
age center) which excludes specular reflection. The surface has a uniform thickness, 
a uniform texture and a spectral reflectance of about 0,98 (see KORTE /4/). 
ng, 
The composition of the layer differs from the standard type, roughly 
described in /9/, which uses Mg0: 
1. mix 20 parts Polyvinylalcohol and 100 parts aqua destillata; heat 
and sift the solution 
2. sift Ba S0, powder and add aqua destillata to get a pulpy mass 
3. take 125 ml of that mass and add 2 ml of the solution 
4. now add aqua destillata until the consistency is ready for the 
spray gun 
e 
  
+ HASSELBLAD MK 70, Reseau 1138, ZEISS BIOGON, f - 60 mm Nr. 5198261