Patent ID: 7421216

Claim:
A development method in which, while stirring a developer which is a mixture of a magnetic carrier and a toner and supplying the toner of the developer, a toner density TD (%) of the developer is measured, and the toner is supplied to the developer, depending on a reduction in the measured toner density TD (%), wherein the toner is supplied to the developer so that the measured toner density TD (%) falls within a range specified by: TD≦{γt·Vt/Nt/ ( γc·Vc )}×100 Vt= (/6)·( Dtav — pop ) 3 Sc=· ( Dcav — pop+Dtav — pop ) 2 Nt=Sc /[(3 0.5 /2)·( Dtav — pop ) 2 ]/2 Vc= (/6)·( Dcav — pop ) 3 (1) where a number average diameter of the magnetic carrier is represented by Dcav_pop (μm), a number average diameter of the toner is represented by Dtav_pop (μm), a specific gravity of the magnetic carrier is represented by γc, and a specific gravity of the toner is represented by γt.