The strain-induced crystallization is generally considered to be responsible for the excellent properties of natural rubber, especially its remarkable crack growth resistance. The crystallinity of rubber is classically studied by using X-ray diffraction (XRD). The XRD technique gives access to the crystallinity but also information of paramount importance on the crystalline phase structure (Rajkumar, et al., Macromolecules 39:7004, 2006), chain orientation (Toki, et al., Rubber Chemistry and Technology 42:956-964, 2004), kinetics of crystallization (Trabelsi, Macromolecules 36:9093–9099, 2003), non-exhaustively. However, this method provides this information at one point. Recently, a new method has been proposed in (Le Cam, Strain 5:54, 2003) for determining the crystallinity, from infrared thermography-based surface calorimetry. In the case of heterogeneous heat source field and large deformations, the method requires combining digital image correlation and infrared thermography. In the present study, this methodology is applied to measure full heat source field in a stretched rubber specimen. The crystallinity as well as its spatial distribution is characterized. © 2022, The Society for Experimental Mechanics, Inc.