Focal Length (mm) vs Brightness (uW)

  10	                15   
  10	                20.5  
  11	                34.5  
  12              	23    
  14.2               	32    
  15                 	25.2  
  40                 	63.3  
  50                	64.9  
  50	                71    
  50                 	73    
  56            	58.5  
  70                    70    
  98                    79
  100                	72    
  100             	73       
  120              	73   
  130              	73.8  
  135                	71.7  

This graph shows the results of our control red sample in the testing stage with lenses of varying focal length.
Results indicate that output is very low (15-34.5uW) with lenses of focal lengths shorter than 20mm.
Output is shown to increase rapidly as focal lengths increase beyond 20mm.
By 40mm focal length lenses, output readings reached as high as 63uW.
From 40mm and up the output remains consistently high, with relatively minor increases at higher focal lengths (80-130mm).
In short, at focal lengths spanning 40-130mm the output ranges from 60-79uW,
with current best being the 11mm diameter, 98mm focal length lenses purchased for the cartridges.

Results indicate that output is very dynamic (15-79uW) with lenses of diameter smaller than 15mm.
Output is shown to stabilize as diameter increases beyond 20mm.
From 20mm diameter lenses and greater, the output ranges from about 63-73uW.
Once again, highest output found from 11mm diameter, 98mm focal length lenses purchased for the cartridges.

My stance is that it focal length has a direct effect upon output results up to about 40mm.
Any longer than 40mm and the output is relatively unaffected.
Lens diameter can have an effect on output results but only so far as ease of lens alignment.
If the light is properly aligned at the center of the lens, a small diameter alone will not cause any negative effects.
It must also be paired with a small focal length.