Complex sentence: Some single exposures, such as "flash and blur" use a combination of electronic flash and ambient exposure, that can be approximated by a Dirac Delta measure (flash) and a constant finite rectangular window, in combination.
Split into simpler sentences: Some single exposures, such as "flash and blur" use a combination of electronic flash and ambient exposure. THis effect can be approximated by a Dirac Delta measure (flash) and a constant finite rectangular window, in combination.