4f2e3cc1   
   From: greif1-nospamhere@rochester.rr.com   
      
   On 6/19/2012 3:47 AM, francesco schillaci wrote:   
   > I'm going to evaluate the MTF of an imaging system.   
   >   I would like to know why spatial resolution is evaluated at the 50%   
   > of the MTF. In the web it is written that it is because it correlates   
   > well with our perception of sharpness, but other web site (wikipedia)   
   > says that is it raleted with the best focus position... Is there any   
   > good reference that explains properly this point? Thank you   
   >   
   Depends on what you use the system for. I find a convenient cutoff to be   
   10 or 15% because that is the range where it becomes difficult  to see   
   and edge or bar pattern visually.   
      
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