  We show that the span of the variable $q$ in the Lawrence-Krammer-Bigelow
representation matrix of a braid is equal to the twice of the dual Garside
length of the braid, as was conjectured by Krammer. Our proof is close in
spirit to Bigelow's geometric approach. The key observation is that the dual
Garside length of a braid can be read off a certain labeling of its curve
diagram.
