Pb with shadows

[bvarillon]

I have just finished the InOneWeekend book and I get the following final render. I don't understand why the shadows look like this, I compare my code with the given one and don't found the error.

More over, the defocus blur is not the same on the two images while they are both produced with the same parameters (aperture=0.1 dist_to_focus=10).

I really don't understand what could make these two images so different.

image produced with my code

image produced with the given code