Originally Posted by
McQ
This is true, but the other reason the sensor can heat up is because it is being exposed so many times in rapid succession. For many situations this is negligible, but for others it could potentially be a factor. For example, if you were to use mirror lock-up (MLU) on a sunny day with a lens that has an f/1.4 maximum aperture, Canon has said that one should be careful because this can really heat up the sensor. A rapid succession of exposures each second could have a similar effect, although not as pronounced. When also taking into account heating of adjacent electronics, as you had mentioned, these factors all contribute to a higher than normal temperature within the camera. However, whether or not this is actually visible in the image is debatable.