I've posted about this slightly in the Sharp DT-510 screen, but I'm thinking this might be a positioning issue on my part, as opposed to a projector issue.
When the projector is mounted on a table, the picture is perfect and level.
When I ceiling mount the projector, before any keystone adjustment the image will barrel out to one side, most noticeably at the bottom. For instance, the image will be level at the left to about 3/4 down, when it begins to get lower. If I turn the projector to the left to try and level out the image, the curve just moves to the center. On close inspection, the whole image will be barreled, kind of like a rainbow.
I cannot keystone correct the barreling away. It only brings the arc upwards.
Why would this only happen when ceiling mounted, even when using keystone correction?