Method for converting digital image pixel values

A method for converting digitized image pixel values from an input dynamic range to an output dynamic range, the method comprising the steps of:

• (a) generating a first histogram of non-log transformed pixel values in the input dynamic range;
• (b) identifying a first limit value for the pixel values in the input dynamic range from the first histogram;
• (c) generating a second histogram of log-transformed values of the pixel values by transformation of the first histogram;
• (d) identifying a population of pixels having desired log-transformed values from the second histogram;
• (e) identifying a second limit value for the pixel values in the input dynamic range based upon the identified population;
• and
• (f) converting the non-log transformed pixel values from the input range to converted values over the output range using the first and second limit values.

A method for determining a useful range of image pixel intensity values in a digital pixel imaging system, the method comprising the steps of:

• (a) determining a lower limit value of the useful range by identifying an intensity value below which non-log transformed values of a desired fractional portion of the pixels fall;
• (b) generating an intensity histogram and a log-transformed histogram based upon the intensity histogram;
• (c) identifying a threshold value for an upper limit value based upon the log-transformed histogram;
• (d) identifying a population of pixels having log-transformed values having a desired relationship to the threshold value;
• and
• (e) determining an upper limit value of the useful range based upon the identified population.