Rendering only what is necessary

Is there a way that I can only render what the camera sees, I want to conserve ram and time. I have lot of objects in my scene?

The camera does only renders what it sees. If it’s rendering slowly, it probably means it has a lot of polygons it needs to think about.

If you mean in Cycles, when it builds the BVH cache, then no, it must load all geometry and textures otherwise it wouldn’t be able to calculate light bounces.