Embodiments of the present invention provide a lensless optical device for acquiring an image. The device can include a light attenuating layer having a plurality of elements, where transmittance of each of the plurality of elements is controllable, and an image detector disposed at a distance from the light attenuating layer, the image detector configured to acquire an image with light that passes through the light attenuating layer. The device also can include a light attenuating layer controller configured to simultaneously control transmittance of each of the plurality of elements independent of each other. Methods of detecting and tracking an object in a scene are also disclosed.