If the object is an actor's head, it will seem most rounded in a closeup that is shot wide, the head positioned in front of the screen plane.
This is not the way 2D directors of photography usually work. The ideal 2D closeup lens is a moderate telephoto, called a portrait lens. A portrait lens foreshortens facial features pleasingly, while a wide angle view seems to stretch out and enlarge the most forward parts of the face, such as the nose.
When a 2D director of photography shoots 3D for the first time, he or she will likely utilize the unfamiliar tools in familiar ways. In other words, they will probably shoot 3D in the manner they shoot 2D.
The result is the cardboard cutout effect a portrait lens creates in 3D, depth without roundness. Likewise, when a 2D production is converted to 3D, seldom is the effort meticulous about the fine depth distinctions in a face. Again, depth without roundness.
Given that the people most likely to work on new productions are those who have established their reputations for craftsmanship on previous productions, most stereo 3D movies, especially blockbusters, are made by 2D movie makers at the behest of studio executives who desire the extra revenue a stereo 3D release can bring.
Consequently, most stereo 3D productions have a 2D look and feel to their composition and editing, with the added effect of depth, most often a depth without roundness. If you see a stereo 3D movie and think, this could just as well have been made in 2D, it is very likely it was shot as a 2D movie using 3D cameras. The full potential of stereo 3D is not likely to be realized by people who think of it as just another special effect, or who even wish 3D would go away.
Would it shock you to learn that the very clip I made to illustrate the previous post was rendered using extreme telephoto CG lenses rather than the standard "wide and close" technique?
It is entirely possible, as you can verify from viewing the clip on the previous post, to show roundness with a pair of telephoto lenses. In the real world, however, this would not be practical. The image below shows why.
Roundness with dual telephoto lenses requires extreme camera separation at great distances from the object. It would be very difficult with live action to align two cameras that are so far apart they cannot be physically connected. Additionally, the two telephotos would see distant backdrops very differently between right and left views. And finally, only a CG lens has the circle of coverage that allows extreme offset of parallel right and left views. In the real world it would be necessary to "toe in" the cameras so that they point at the object and later, digitally correct for the headache inducing distortion this creates. (My apologies for technical terminology; I'll be explaining these concepts in future posts.)
Thus, my use of CG telephoto lenses to create roundness serves as proof by exception that "wide and close" is the best practice.
I leave you with a quiz question. Why did I use telephoto settings instead of moderate wide angle settings to create a 3D screen depth comparison movie? Hint: Think about how much of a globe you would see from close up.
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