Computers, video cards, disk drives, projectors and more.
i had a play around with an Optoma ST with an iPhone taped to it to use the spirit level - 1m from the wall so the image is 2m wide. here's some sketches of the results - not to scale. i wouldn't push the projector much further than 24 degrees from horizontal because the keystoning gets excessive and brightness starts to fall off. but up to 24 degrees i reckon mapping is no problem. i dropped it to -21 degrees, which - using a little table as a stand - got the image onto the floor. the top edge started to get a bit small and bright. i regularly prop this machine up with its front paws on the floor, so that the bottom edge of the image is also on the floor, and map it back to rectangular.i guess thats at about 16 degrees. i hope this helps....