<p>The use of renewable fuels, such as hydrogen, in internal combustion engines necessitates the development of innovative combustion strategies, which in turn demand a profound comprehension of the underlying ignition phenomena. Consequently, there arises a necessity for advanced or novel measurement techniques that can offer further insights into these phenomena. As part of a study to better understand the ignition phenomenon, this paper presents a modified Background Oriented Schlieren (BOS) method developed to study the heat transferred from sparks generated by spark plugs utilising a projected background in combination with the fast checkerboard demodulation (FCD) technique. This method provides a flexible and more suitable alternative to other BOS techniques for analysing spark ignition phenomena due to the high-resolution visualisation (spatial and temporal) even at higher pressures. Using this technique, the temperature fields generated by the spark were estimated using a simplified calibration. This work also demonstrates the use of the aforementioned method to obtain a high spatial resolution, high-speed visualisation of the heat transferred from the spark to the surrounding non-combustible medium, and the interaction of the spark with the flow field at 11 bar absolute pressure.</p>