Final Project

So, I finshed a few rolls of film and I went to develop them and they were underexposed again. I can't figure out what is going on. I made sure there was enough light and I watched the light meter on the camera. It is so strange. Two photos of my mother came out and the rest of her, sitting in the same place, came out blank. This makes absolutely no sense to me. Is this from the way I develop the negatives. It seems like the the photographs in the middle of the rolls of film come out blank and the rest are fine.

So discouraging.