lesbentley has it right, but stops just short of why changing the focal length seems to change the perspective. That hole in the paper, of different apparent size, gets squeezed or stretched to fit an image of fixed apparent size. Incidentally, all a longer lens does is magnify the final image, whether with glass or with a "digital zoom". Now, do you ever use a background image? What lens was that shot with? If it was shot with a wide-angle you can always crop the edges to match the angle of view of the Poser camera, but getting the right size could be tricky. But that may be why something doesn't look quite right. The thing to watch for is parallel lines converging in the background. That's the big give-away.