Learning and evaluating the overlapping roles of physics and physiology in perceiving contrast and resolution in microscopy

Simple compound microscopy is widely used across the globe. However, contrast and resolution fascinate students and are difficult to learn due to their limited practical experience. Although the laws of physics have been derived thoroughly, their real implementation in the human body is uncertain. This study quantifies contrast and resolution through human perception and technological tools and assesses the degree of overlap between physics and physiology. Thus, an opaque repository for a compound microscope with a mobile holder is devised to capture the images of Leishman-stained smears and USAF targets. Another receptacle is fabricated to hold coloured filters against a light bulb, which projects on the microscope mirror through a connecting pipe. The images with a different sequence of filters are subjected to analysis by volunteers and using digital image processing techniques. The perception of contrast and resolution through the human eye and digital processing shows an overlap of 82.57% for contrast and 76.40% for resolution. Also, participants opt for contrast (81.66%) against the resolution (75.51%). The preferred sequence of light for contrast and resolution is white > green > blue > red and white > blue > green > red, respectively. Green > blue > red is preceded by white when both contrast and resolution are examined concurrently. Thus, the integrated role of the two disciplines in learning contrast and resolution has been studied and evaluated practically beyond the limits of the textbook on a hands-on basis. Simultaneously, the subjective selection of resolution or contrast using low-cost colour filters is an affordable approach to upgrade a microscope. Graphical abstract: [Figure not available: see fulltext.]