What is the difference between ratiometric imaging and calcium imaging?

Features of Ratiometric Imaging:

• Is a technique that involves measuring the intensities at two or more wavelengths of an excitation or emission spectrum in order to detect fluctuations in local environment
• Involves the use of a probe that is specifically sensitive to an environmental parameter such as pH, polarity, ion concentration or viscosity
• Is based on the use of a ratio between two fluorescence intensities

 Features of Calcium Imaging:

• Is a microscopy technique used to optically trace and measure cellular calcium signals
• Involves the use of calcium indicators, which are fluorescent molecules that respond to the binding of calcium ions by fluorescence properties
• Is based on the sensitivity of the calcium indicators to fluctuations in specific environmental factors such as temperature, pressure, pH, ionic strength, and proximity of other fluorophore species