In addition to the standard EOS-1N there was another, specialised model in the range — the EOS-1N RS, introduced in 1995, with a permanently attached power drive booster. This camera has a fixed pellicle mirror so there is no viewfinder black-out at the moment of exposure. The fixed mirror allows high-speed continuous shooting at a top speed of 10 frames per second, with a shutter release lag as low as 6 ms. There is a cost to this however: slightly less light reaches the film, as some is always being directed up to the viewfinder and optical quality loss. By the time of the release of the next generation EOS 1V, considerable technical improvements to the standard camera design meant that Canon no longer offered RS model variants.