It would be dependent upon the types of operations taking place on the line. My recommendation would be to study the processes taking place carefully as well as talk to the people doing the work in order to get their input. You may have good illumination levels but if the operators concerns are with shadows or glare, may need to look at the luminare designs or simply supplementary task lighting.
Detailed or high precision work tends to utilize higher levels of ambient illumination. We do a lot of precision assembly and run about if I remember correctly use around 60-100 foot candles (measured at the work surface) with full spectrum type bulbs. Essentially, we have an expensive setup to operate and maintain but it is necessary for the type of work being done.
Regards,