I too want to know this 0.98 value and request ranjith and manoj to share the reference.
However just to put some valuable information about Lux in pharma I have summarized few quick bites for you all.
Just to understand what is Lux (lx): This is the illuminance produced by a luminous flux of one lumen, uniformly distributed over a surface area of one square metre. One lux is equal to one lumen per square meter.
Luminous Efficacy (lm/W): This is the ratio of luminous flux emitted by a lamp to the power consumed by the lamp. It is a reflection of efficiency of energy conversion from electricity to light form.
So from the above two definitions I presume this 0.98 could be either coeficient of utilization(Cu) (Luminous efficacy) or its a efficiency in Foot Candles.
as from the below Measuring Units of Light Level - Illuminance we come to know that Illuminance is measured in foot candles (ftcd, fc, fcd) or lux (in the metric SI system). A foot candle
is actually one lumen of light density per square foot; one lux is one lumen per square meter.
• 1 lux = 1 lumen / sq meter = 0.0001 phot = 0.0929 foot candle (ftcd, fcd)
• 1 phot = 1 lumen / sq centimeter = 10000 lumens / sq meter = 10000 lux
• 1 foot candle (ftcd, fcd) = 1 lumen / sq ft = 10.752 lux
I have given below few reference of Visual inpspection, hope it will help you in understanding the concept of Visual Inspection:
USP 〈790〉 VISIBLE PARTICULATES IN INJECTIONS
EP 2.9.20. PARTICULATE CONTAMINATION: VISIBLE PARTICLES
JP 16: 6.06. Foreign Insoluble Matter Test