Polarity of the colour difference signals
Both (R – Y) and (B – Y) can be either positive or negative depending on the hue they represent.
Overview of the Polarity:
- For any primary, its complement contains the other two primaries.
- Thus a primary and its complement can be considered as opposite to each other and hence the colour difference signals turn out to be of opposite polarities.
- This is illustrated by the colour phasor diagram of Fig. 1.1.
- A purplish-red hue is represented by (R – Y) while its complement, a bluish-green hue corresponds to – (R – Y).
- Similarly (B – Y) and – (B – Y) represent purplish-blue and greenish yellow hues respectively.
- Green colour is obtained by a combination of – (R – Y) and – (B – Y) while cyan is obtained by a combination of – (R – Y) and (B – Y) signals.
Figure 1.1 Colour circle showing location and magnitude (100%) of primary and complementary colours.
- Any one of the three primaries or their complementaries can be obtained by a combination of two of the above four signals.