[jesusrambo]

I would be inclined to agree with xmendude that your problem most likely lies in your thresholding. Setting 0s for all values would, yes, detect black objects, but only perfectly black objects with absolutely no color at all. My bet is as soon as you have any light at all in the image the values would no longer be 0 for R, G, and B.

Out of curiosity, what's your setup that you find it viable to look for only perfectly black objects?