Sometimes I feel like I'm driving in the snow with all this system calibration. You turn right when you want to go left. Turn too far and if you're lucky you hit the hillside and wait for some helpful citizen to come along with a tow line to pull your radiator off. (OK, I was the helpful citizen. How was I supposed to know the brace behind the Fiero's bumper held the radiator. The driver was really nice considering). I've heard that instead of being calibrated to 18% gray, most meter manufacturers include a "K-factor" which is approximately a 1/3 stop deviation away from 18% gray. In the specifications for my meter, the Calibration Constant is 12.5 for reflected light. I have the opportunity to change this to any number I want. Does the K factor improve the accuracy of my meter? Does it compensate for flare? Should I try to determine my own K factor?