I have liked your responses to the MTF questions and wondered if you could help me clear up an issue I have encountered.
I have a Canon 7D with an assortment of EF and EF-S lenses. The current issue of CT Digital Photography Magazine has an article that compares the 7D with a Nikon and Sony. They show that with a Canon EF-S 15-55mm f2.8 lens the resolving power at medium focal length on center axis is 1418 lp/mm. I do the math and get 95.17 lp/mm.
I understand that this value is for the camera system including the sensor and lens. I am finding that the equations for deriving the resolving power for the camera and lens don't seem to work with this value. I know that the 7D sensor has a native resolving power of 116 lp/mm and I know that the system value will be less that the lowest resolving power item.
I would like to be able to determine the value for the lens, but if I use 116 lp/mm and 95.17 lp/mm to solve for the lens, I get an impossible value for the lens. I have the same issue when using measurements in terms of lw/ph. Is there a relationship between the 1418 lp/mm and the 3456 sensor height?