The focus mask is hardly flawless. It is optimized for studio work and not landscape work. My experience has been that the mask is indicating in focus for areas of an image that are clearly way out of focus. Subject matter is important for successful use of the focus mask.Is the C1 focus mask flawless? Surely its a great help, but shouldn't someone check "how good is it?" - and what level of precision it has - on a camera and back.
Victor