This Saturday at the Arts League of Lowell gallery, 307 Market Street (close to the corner of Dutton and Market), meet photographer Paul Richardson and see his outstanding photographs of Lowell buildings and places. The reception is 4 to 6 p.m. Cameo Diner. Olympia Restaurant. Bridge Street downtown. Pawtucket Falls. Owl Diner. Muldoon’s gas tanks. Cote’s Market. Francis Gate. Skylines. Streetscapes. For a preview, check out his website. But see these for yourself in vivid color and sharp black-and-white. The compositions are fine-tuned.