Standard deviation of color matching(sdcm) 
1 sdcm actually refers to the distance the measured value deviates from the target value.

2 If you want to indicate the sdcm of the measured value, you must provide the target value and calculation formula.

3 In an ellipse with a sdcm of 5, the sdcm of a point on the curve is 5. The color coordinates of all points in the circle are less than 5.

4 These ellipses can be expressed by certain equations.

5 IEC stipulates that the color coordinate of the lamp shall not deviate from the rated value (x, y) by 5 sdcm. That is to say, the color coordinates of the lamp should all be within the prescribed ellipse.