Exact same scene but different rendering times?

mlominy

By changing nothing else in my scene other than a camera angle and Focal Distance, I've observed radically different rendering times, (8 min vs 23 min, for instance).

How rendering the same scene from two different cameras can affect rendering time?

What camera parameters affect rendering time?  

Richard Haseltine

Assuming you are using the default Progressive options in Render Settings the render stops when enough pixels are "converged" - that is, when they have received enough hits to have reached a settled value (how settled they need to be is determined by the Render Quality). Changing the camera angle and depth of field will both potentially affect that, by what is in the field of view and how sharp it is, and so will affect the render time. For example, if one render is looking at a well-lit wall and the other is looking at a shdowy niche that receives light only when it bounces off other surfaces then the render with the niche is likely to take far longer than the one with the wall.

jestmart

Certain things take longer to render because they require more complex calculations.  Changing the angle or focal distance may have caused one of those certain things to occupy more of the image.