Light and Color Sensors Calibration

The light sensor reads light intensity and its raw value reading ranges from 0 to 1023.  By using the Calibration Tool for light sensor that's built in in Mindstorm NXT-G software, one can NORMALIZE the light intensity reading to range between 0 and 100.  You want to calibrate the light sensor because
1)It is easier to work with a number between 0 and 100.
2)During the calibration, you already tell NXT brick/brain about the MINIMUM, i.e. the darkest black, you can find on the mat, and the MAXIMUM, i.e., the brightest white you can find.  So the NXT brick/brain doesn't need to worry about any raw value reading that's beyond the minimum and maximum.  This allow you to work with a better resolution.  That is, it allows you to read the different grey area, say, from 1 to 99.


The calibration procedure is best explain in this Millerbots instruction video. 


As for the color sensor, the Mindstorm NXT-G software does not have an equivalent calibration software for it.  Moreover, there is no proper built-in viewer to read the color sensor reading from the small viewing window of NXT brick.  I recommend reading the light intensity reading of a color sensor directly from the laptop, as explained in this video.  And I recommend a manual "calibration" procedure as below.  You place the robot/color sensor on the darkest black, make a note of the laptop reading.  This will be your manual minimum value.  Then you place the robot/color sensor on the brightest white, make a note of the laptop reading.  This will be your manual maximum value.  Therefore, if you need a threshold for line following, it can be the average of the two values.

P.S. I have found the line following performance using either a calibrated light and color sensor is about the same.