Hi All,
I have been messing with cameras (namely the A7S) and using different lenses for different purposes. As most may know, longer focal lengths are more suited for portraits, shorter being for landscapes etc. The reasoning behind this (at least from a visual standpoint) is that longer focal lengths i.e 80-200mm showcase a persons features, and makes them appear more flattering. Wide Angles do the opposite for human subjects.
With all this said, I took the liberty to just showcase different Focal Lengths on a Lego Subject in Blender, with camera at same position to show (1) How focal length effects zoom and composition (2) How Human/Human Like subjects appear much better at longer Focal Lengths. I used a longer focal length (80mm) for my Lego Minifigure post in Critiques, and the results tell the tale. Before I had performed/experimented with the A7S and Blender Cameras, I had been using the standard Blender 35mm lens. The portraits did not look good. The 80mm looked significantly better IMO.
Guide:
Fisheye 1mm-24mm
Wide Angle 24mm-50mm (Approximation)
Intermediate 51-80mm
Long/Zoom 81mm-200mm (Or in theory Infinitely Longer)
With a Fisheye and WA lens, keep in mind the immense distortion that can come with the territory. The camera needs to be VERY close to even get the subject in frame. This is why portraits look bad because getting close to frame the Subject = More Distortion. Further away, the distortion is less, but you canāt see your Subject. But for landscapes, they yield great results, and make the landscape feel grand and truly awesome.
Intermediate Lenses are used in real Photography due to their fairly good portrait results, and you can get a lot closer than with a Longer Focal Length Lens. These are still ok for portraits, but in CG, they are not ideal. Can be used for either landscapes or portraits, but yield āmehā results. Camera doesnāt need to be far or close to the subject.
Long/Zoom Lenses make for good portraits, but you must back the camera up A LOT. This can suck in real Photography if you have limited space. But in CG, most times we have A LOT of space. When using a Long Focal Length, back that sucker up! Landscapes do not come out so wellā¦
This test shows how Focal Length changes the Zoom and composition of an image at a fixed distance:
Distance: Appx. 3.2m
This test shows how framing the same image with different focal lengths yields distinct results:
Distance: Variable
As soon as I get a landscape scene going, I will update on that. But for now, you see the Portrait results 
I hope to help other CG Artists understand Focal Length