Thank you very much Dan, the distribution works perfectly.

But I don't really understand what you mean when you said

Dan Ebberts wrote:If you just want the layers' opacity to be a function of the layer's distance from the camera, that's easier - but you still have to define the parameters.

Thanks again !

Hi there, I'm new in this site, that i discover recently. So first of all Hi !!! Please apologize my poor english since it's not my common language. I'm a newby in expression and i have an animation to make : I have 300 photos that i want to distribute over a solid of 3000 X 500 px. A camera over it...