
* exif data
** provide robust extraction of exif data for generation of hdrgen
   script


- pfshdrcalibrate:  
  - consistent use of the 0 - 1 range of pfs streams
    - this affects the Gaussian weighting function and
      mostly the Robertson method

  - for Mitsunaga & Nayar: the output curve is centered at 0, not at 
    the mid-value of the intensity range -> this should not work well
  - actually, the behavior of weights is a bit weird
  
  - unified response curve treatment - only one apply_curve function 