The refractive index of current eyeglass lens materials ranges from 1.498 (CR-39 plastic) to 1.74 (a specific variety of high-index plastic). So for the same prescription power and lens design, a lens made of CR-39 plastic will be the thickest lens available, and a 1.74 high-index plastic lens will be the thinnest.
Principal photography on the film began on April 25, 2016, in Pittsburgh, Pennsylvania, in the Hill District, and wrapped in mid-June 2016. Fences was released in the United States on December 16, 2016, by Paramount Pictures, received positive reviews and grossed $64 million.
One of a number of 1979 gang movies which were first released in that year. The pictures included Walk Proud (1979), The Warriors (1979), Boulevard Nights (1979) and The Wanderers (1979). Then in 1980 came another New York gang movie, John Carpenter's Escape from New York (1981).