Not really. First of all there's multiple samples per pixel for anti-aliasing and even more when doing stocastic sampling from the circle of confusion for DOF a

Not really. First of all there's multiple samples per pixel for anti-aliasing and even more when doing stocastic sampling from the circle of confusion for DOF and motion blur, so you normally need 128-512 samples per pixel. Then for each light (unless you randomly sample a light each time - which introduces more noise), you need to test occlusion from each surface hit to check for shadows. So each pixel sample that has a solid alpha (it hit an object) needs to be tested against lights with a ray. Then with GI pathtracing, you need to bounce the light around the scene even for diffuse (non-shiny) surfaces. The article's still mostly rubbish though...