My D3400 obviously has a light meter built in. I have a need to verify that a white surface, about a foot square, is illuminated to a minimum of 1,000 lux. I have the two kit lenses which come with the D3400. Does anyone know of a formula to back calculate the lux level based on the shutter speed which the camera computes based on a given aperture or some similar method?
TIA,
Ken
TIA,
Ken