The invention provides a viewing optical system positioned between a viewing plane as a virtual plane and an eye point. The colorant dispensing system includes a supply hopper to selectively retain and discharge dry colorant. Voltage step-down portion may compare a reference voltage with an internal voltage and control an output current accordingly. A partial block update operation is performed by writing a second set of user data to a second block at a second PBA, the second set of user data updating a portion of the first set of user data in the first PBA.