Embodiments relate generally to the health field, and more specifically to a new and useful method for measuring detecting physiological characteristics, such as heart rate, of an organism. In one embodiment, a method includes detecting one or more surfaces associated with an organism, and receiving components of light reflected from the one or more surfaces of the organism. The components can be represented as data from a light capture device. Also, the method can include identifying subsets of light components, each subset of light components associated with one or more frequencies, identifying at a processor a time-domain component associated with a change in blood volume associated with the one or more surfaces of the organism, and extracting a physiological characteristic based on the time-domain component.
