If you've seen newly wheat-pasted posters around town, smothering poles, electrical boxes, and window boards, there's a good chance it was the work of Poster Midget, a small postering operation competing with the older, larger, more established Poster Giant [see "Poster Child," May 19]. This poster isn't particularly sexy all by itself, but seeing a bunch of them pasted in a grid, edge-to-edge, creates a dynamic field of purple dots on an apparently seamless wall of blue.... It's a breathtaking illusion that proves how you post is as important as what you post. CORIANTON HALE