The Challenge of Digital Design Starts with the Exam.

The article presents suggestions for understanding the assumptions made by lens designers when they create lens. For the assumption that testing is done with the lines of sight at 90 degree, use of inclinometer is suggested. For the assumption that line of sight are passing through optical center of test lens, use of pinholes in refractor cells and vertical prism is recommended. Proper way to check if chart it at right position in a short refracting room is mentioned.