The invisible to camera option makes an object invisible to the camera, at least as seen directly.
However, the object will still cast shadows, and will be visible in reflections from other objects.

The invisible to camera option is useful in a few different scenarios:

• Hiding a wall in an architectural rendering so there is more space for the camera.
• Hiding an object when doing a shadow pass, so that the object does not get in the way of the shadows cast on the ground. See the Compositing with shadow pass tutorial for more information.
• Hiding a light source, where the light source would usually be visible in the 'shot'.

Piggy bank with piggy visible to the camera

Piggy bank with piggy invisible to the camera. Note that shadows from the piggy are still present.

Setting to invisible in the Indigo GUI

To make an object invisible to the camera in the Indigo user interface, first select the object with the pick object tool:

Then check the invisible to camera checkbox in the Property Editor:

The invisible to camera option is in Indigo Renderer only and is not available in Indigo RT.