EPM Tech Tip 039: Densitometer Use and Calibration Procedure

This Eastman Park Micrographics (EPM) guide describes the principles of correct densitometer use and calibration for measuring film density so that readings are accurate and repeatable.

Highlights

• The densitometer should not be located in the darkroom.
• Turn the unit on at the start of the day and leave it on.
• Aperture size should suit the image reduction ratio; usually the largest usable aperture gives the best average density.
• Clean the reading surface once a day with a lint-free cloth slightly dampened with water.
• Follow the manufacturer's preventive maintenance schedule.
• Calibrate the unit at least once a day with the manufacturer's calibration patch.
• The Quality Assurance Lab density strip is for correlating readings only, not for calibration.
• Check the zero before each reading and do not rush readings.
• Most densitometers require the film to be read emulsion up and in the center of the patch.

Description

Density measurement accuracy depends on environmental conditions, keeping the unit steadily powered on, selecting the right aperture and regular calibration. Calibration must be done with the manufacturer's reference patch, and the strip sent by the Quality Assurance Lab is used only to compare your unit's readings with those of the lab's unit.