Recovering the camera response
Method 3
•Calibrate the response function from several images
–Consider taking images with shutter speeds 1/1000, 1/100, 1/10, and 1
–Q:  What is the relationship between the radiance or pixel values in consecutive images?
–A:  10 times as much radiance
–Can use this to recover the camera response function 
For more info
•P. E. Debevec and J. Malik. Recovering High Dynamic Range Radiance Maps from Photographs. In SIGGRAPH 97, August 1997
response curve
exposure
@ radiance * time
=
pixel intensity
=