What's the difference between Copybook for calligraphy and the original stone?

Compared with the original film, the refined film is about 80% or slightly higher, and the ordinary film is less than 60%. Once again, it is worthless for two reasons: for a time, many original plaques have been severely eroded by wind and rain in nature for a long time, and they are artificial and selfish, and some people will destroy them after copying.