A zoom lens of a novel configuration suitable for a collapsible lens barrel is disclosed. Installation space is reduced and a compact configuration is achieved by providing a partition that divides the interior space of the housing into two regions into an upper bay and a lower bay, mounting the engine in the upper bay and mounting air intake duct in the lower bay at a location directly under the engine. The slave unit articulated arm utilizes controlled segments and articulated arm joints arranged in the same order and having the same relative ratio of lengths between themselves. The quantized intensity level of a pixel may fall into one of a first pixel class, a second pixel class, or a third pixel class, for example, a dark pixel class, a dim pixel class, and an acceptable pixel class.