The correct answer is Henryk Ross.
Henryk Ross had a much more privileged life in the ghetto than Esther Brunstein because he was a photographer for the German army. Therefore, he could live more comfortably, safe and get more food.
Moreover, as Henryk was a photographer, he was in charge of producing propaganda and identity photos for the Department of Statistics in Lodz Ghetto (in Poland). He could access to film and other processing facilities in the ghetto that he used to document the living conditions and the suffering of the Jews there, secretly.