Equation
ν = 1000 / (2p)
At 5 µm pitch, one millimeter contains 200 sample positions. A cycle at the Nyquist limit spans two positions, giving 100 lp/mm. A lens MTF curve supplies the contrast at that frequency.
When to use it
Use the center-to-center pixel pitch of a uniform sensor along the axis of interest. Pixel pitch and photosensitive area can differ. Color filter arrays, binning and image processing require additional assumptions.