Try to think of it as the zoom on your camera. You can zoom in and see objects close up, but lose the depth of your image. Or you can zoom out to fit more in the frame and lose detail. Whatever you do, don't overuse it.

---

[Link to www.3dprevis.com]

Yeah its important to try and stick to typical lens values. If you are doing a landscape use a wider lens for closeups use a narrower lens to avoid distortion. Using the lens presets is a good place to start. If you try and mimic real cameras you will get believable results like say rendering to 16X9 widescreen with a 35 millimeter lens for a typical film type camera. But in film they will rarely just use one lens for the whole film, swapping lenses depending on the shot.

---