Please resize to 1024×768. This is the maximum size in pixels that our projector can project, it is in the ratio of 4×3.
Some cameras have sensors in this ratio, mainly compacts and bridge cameras, and now the new 4.3rds system from Olympus and sony.
Most DSLR though are 6×4 which gives us a size of 1024×683 if reduced to fit (landscape).
So we only have to bear in mind the maximum of each dimension 1024 for the width and 768 for the height.
We could have a letterbox size of eg (1024×400) or a square (768×768) or anything in between.