What does virtual focus of projector mean?

Virtual focus of projector means that the lens will focus halfway or the clarity of one area will deviate from other areas

For example, the top is clear and the bottom is blurred, and the bottom is clear and the top is blurred after adjustment.

virtual focus: take the up-down virtual focus as an example. At this time, only the transition definition from up to down to middle can be adjusted, that is, the definition of up and down is almost the same. ?

As a means of photography, virtual focus, just like the rhetoric in the article, needs to find a foothold for it.

virtual focus is a derogatory term in photography. The most taboo of pictures is virtual focus.

Virtual focus picture means that the whole picture has no focus, and nothing is clear. Technically speaking, it is a waste product.

But now some photographers can do the opposite and discover the mystery.