Hello First of all, I was told this is a physics problem. If it's incorrect, I apologize. I have an image I want to know the length of the black ship (the ship which is carrying a ship). Lets assume that I know the length of the text on the ship (I have a reference object). Is this related with camera lenses? How is object becoming smaller on the image (bigger distance) and at what rate is the size decreasing? I was doing some tests and it seemed to me that it's not decreasing by some constant. I understand that it's related with angles (bigger angle means that the end of the object with be the furthest and the smallest on the image). Can somebody please help and give me the right directions?