A method of controlling an imaging system for a Head Mounted Display (HMD) device. The method comprises capturing an external scene, for example using a camera, determining an attenuation pattern, for rendering a filter area. The method also comprises determining, based on the captured external scene, a compensation pattern to for compensating at least part of the filter area, attenuating the external scene using the attenuation pattern and generating a holographic image of a virtual object, the holographic image including the compensation pattern.