Solving the "magnification irony" in microscope-based reflected light image analysis of conifer tree rings

This paper describes a technique for allowing the magnification of a microscope to be changed and still obtain quantitative reflectance values for low-magnification reflected light image analysis of conifer tree rings. A remotely controllable digital camera is used to capture images, and a multireflectance gray standard is used to calibrate the luminance response of the camera across a range of reflectances. The imaging system was tested by measuring two conifer rings of differing widths and densities at several different levels of magnification. Upon adjusting the camera and converting gray values to true reflectances, the earlywood maximum and late-wood minimum reflectances of each ring were essentially identical across all magnification settings. Total ring widths were also equal across all magnification settings. The "magnification irony" is solved for microscope-based reflected light image analysis of conifer tree rings, and reflected light image analysis of conifer tree rings should become more prominent in future dendrochronological investigations.