The Short throw R04 lens exhibits rounding or shadowing on the corners. What is wrong?

• The V12H004R04 Short Throw lens is a center centric lens. From the center point of the vertical lens shift adjustment, there is a 6 inch range up or down before the corners start to exhibit shadowing. This is the standard specification for the R04 lens. If the corners are rounded or shadowed during the initial installation of the lens out of the box, Epson recommends making the vertical lens shift adjustment (up or down) to correct the corners.
  
  Related references
  Adjusting the Projected Image (Lens Shift)