Yes, you've purchased a lens that will not give you any room to move within the projected image circle. Normal focal length for 8x10 is 300mm or 12 inches. You have purchased a 240mm or 9.5 inch lens, which, if it covered the 8x10 format, is a moderate wide-angle, similar to a 35mm lens on a 35mm camera. Not ideal for portraiture.

Peter Gomena