I bought the Modern Photography magazine lens testing kit from the early 70's and have been using it for all my testing since. The kit came with a 16 page manual, test charts and a magnifying loupe to inspect your negatives. I have been able to preserve the manual in excellent shape and four of the charts like new. In the manual you are told what distance the lens should be for each lens focal length and what camera format, 35mm, 6x6 or 4x5. The manual has charts which convert the line pairs on the charts to resolution in Lines Per MM. (LPMM). I find the resolution increases in LPMM (of the same lens) as the digital sensors get better. It tells me that the resolution limits are not caused by the lens but by the sensor (in many cases). By checking every lens at every f stop I can also see where diffraction is creeping in and it's not like hitting a brick wall as some would make you think. As an electrical engineer and past design engineering manager and quality control manager, now retired, this type of testing is very interesting to me.