The photograph you have attached shows the bomb aimer using the bombsight. Compare it to the similar photo on this link.
https://en.wikipedia.org/wiki/Mark_XIV_bomb_sight
If the photo was taken with a flash camera (not a flashbomb), the white blob is probably a reflection off something in the plane.
The photoflash bombs would probably have been carried in the bomb bay.
Here is an example of one type of photo flash bomb, I am not sure what would have been used in this case.
http://www.harringtonmuseum.org.uk/M46Photoflash.htm