All three standards, ISO/IEC 15416, ISO/IEC 15416, and ISO/IEC 29158 has specific light geometry accepted by each standard.  Each standards has nuances but references light geometry are describe below in this page

All three standards, ISO/IEC 15416, ISO/IEC 15416, and ISO/IEC 29158, require that Reflectance Calibration is performed with a calibration card available from Omron. Reflectance Calibration maps the reader’s measurement of gray values to actual reflectance levels, establishing a conversion for the verification software to measure and output valid results for tests such as Contrast, Modulation, and Reflectance Margin. 

Only apply on lable barcode verification.

Conformance calibration is to relate current lighting geometry to the know reference geometry.  When performing, it is important to copy aperture size to the calibrated card value.  OMRON conformance card part number is 98-CAL20