The canon dioptric lens eg 3 provides near and far sighted users with a clear viewfinder image without wearing spectacles the dioptric adjustment lens fits into the eyepiece holder of the compatible camera the dioptric lens eg 3 is compatible with the eos 5d mk ii iii eos 6d eos 7d eos 1d mk iii iv eos 1d x and 1ds mk iii