Ok Dave, I hope this helps. To get a consistent point of reference, I set the camera on manual focus, then set the focal distance at about 4 inches. Since you said you were buying for a 50mm lens, I set the focal length on my zoom lens as close to 50 as I could get.
With no lenses added.
With +1 lens.
With +2
With +4
With +10
Here is an example with my camera set at about 100mm and 12 inches from the subject.
100mm no added lens
100mm with +10 lens.
