Should I use L* a* b* or L* C*ab H*ab specification?

It is often convenient to consider a single slice though colour space at constant L*. Although it is possible to represent a point in the a*-b* plane by its cartesian coordinates a* and b* it is often better to specify the polar coordinates C*_ab and H*_ab.

It is dangerous to attempt to interpret the qualitative colour difference between two samples using the a* b* representation. For example, even though the a* axis is the red axis, a sample with a large a* value would not necessarily appear redder than a sample with a smaller a* value. Hue is not uniquely defined by either a* or b*. The use of C*_ab and H*_ab leads to a more intuitive representation of colour.