Masked (or flat) widescreen was introduced in April 1953. The negative is shot exposing the Academy ratio using spherical lenses, but the top and bottom of the picture are hidden or masked off by a metal aperture plate, cut to specifications of the theater's screen, in the projector. Alternatively, a hard matte in the printing or shooting stages may be used to mask off those areas while filming for composition purposes, but an aperture plate is still used to block off the appropriate areas in the theater. A detriment is that the film grain size is thus increased because only part of the image is being expanded to full height. Films are designed to be shown in cinemas in masked widescreen format but the full unmasked frame is sometimes used for television, known as an open matte. In such an instance, a photographer will compose for widescreen, but "protect" the full image from things such as microphones and other filming equipment. Standardized "flat wide screen" ratios are 1.66:1, 1.75:1, 1.85:1, and 2:1. 1.85:1 has become the predominant aspect ratio for the format.