	One advantage to the alternative conception of vision is that it makes it much easier to say what a shadow "is". It is no intellectual challenge to grasp how the arrangement of light sources and objects in the real world cause us to perceive shadows, but it is difficult for ontologically minded people to formulate in common language what a shadow "really is". A shadow is not the area of ground on which the light falling is less then what it is in the surrounding area, because if I move, my shadow moves, but the area of the ground on which it was falling before I moved is still in the same place. Also, I can turn off the lights, which will make my shadow disappear, although the brightness of the spot on which it was falling hasn't changed. It is strange to say a shadow is darkness surrounded by light, because darkness really isn't a thing. If we adopt the alternative conception of vision however, and say that the shadow is a demarcated area of the visual field that is darker then the surrounding areas, it becomes much easier to talk about. In the visual field, dark perceptions and light perceptions really are of different quality, rather then darkness just being the absence of light, as is the case of dark and light in the physical world (because if you take a spot of the visual field, and remove whatever perception is there, by removing the photoreceptors there, it gets "filled in" by your brain with whatever the surrounding color is, but if you take an area of the real world, and somehow stop photons from bouncing off it, it will be black). In talking about the shadow as an area of the visual field, we can explain easier what is meant by a shadow moving, and disappearing. It is as easy as talking about a character on a tv show moving across the screen, or disappearing from the screen. In the alternative conception of vision, shadows have no indirect object, they are not reflective of any "thing" in the physical world. They don't need to be described as such, because it is easy to describe what conditions of the physical world cause the certain area to be darker on the visual field. Similar arguments can be made about rainbows, the sky, spots (as in "seeing spots" when you're sick), mirages, and holograms.
	Unlike the case with hearing, there are real descriptive advantages in this way of talking, especially in certain domains, which is probably why certain elements of the alternative conception are used by astronomers (saying "Star A is 5 seconds of an arc away from star B", though one may actually be ten times further away from us, or "The celestial sphere rotates at an angle of such-and-such degrees" even though it’s the stars that are fixed and us that is moving). Though the disadvantages would make everyday descriptions of things much more cumbersome. There is not much need for debate over which one is better and how people should really talk, as language is flexible enough to accommodate both. It is just necessary to preface certain statements with a description of how you are talking. 
