Just dashing this off -   
      
   Detecting absorbance changes in a piece of filter paper by diffuse reflectance   
   is   
   useful in color-change diagnostics.   
      
   I was talking to an engineer at a co. where they have have such a test. He   
   said measuring the reflection was tricky with a single PD, which was sensitive   
   to sample position, etc.   
      
   He thought it required an integrating sphere approach.   
      
   Is there a "half baked" approach to getting the benefits of an int. sphere?   
      
   jb   
      
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