It is possible to reconfigure the unit to be like one of the old small graphic arts Xrite densitometers that were used with light tables. The evenness of illumination on the light table was always an issue with these 'pocket densitometers'.
In this unit it is possible to mount the photodiode to the back of the case. The metering would be done on a light table, as with the old graphic arts densitometers. A cradle or spotting arm would define the area to be measured and the meter would then swing down on the arm or nestle into the cradle to take the measurement.