An old book "Lootens on Enlarging" describes the pictorial darkening of the corners of your prints. Say you took a portrait and the upper-left corner the frame holding the drop cloth shows. With flashing, you darken the upper left corner with maybe 5 seconds of light from an 8-watt bulb as you shield the rest of the print with cardboard. It's like burning but without a negative. No additional detail, it obliterates and plunges that corner of the print to black.
Originally Posted by PKM-25
Printing full frame has been done before, so people have gotten tired of it before... I prefer it though I concede it is neither the best route to go nor something anybody should do without thinking it through.