Originally Posted by sundialsvc4
But, beyond that,
we are both "free" and "encouraged" to 'cheat.'
The tornado in Wizard of Oz
was basically panty-hose. The alien-architecture in Star Trek
was made from repainted cast-offs from "Mission: Impossible." And nobody cared.
It was cheap, it was fast, it was good-enough, and it was "Cut! Print it!"
I agree, but the question is in cheating quality. If you use cg tricks, you complicate the scene setup. Also in real life you already have a realistic scene. In cg you work from the opposite, and each time you break the rules you bias the rendering to the unrealistic result. In photography you start cheating from light position, light blocking and camera settings. Then you manage reflections and diffuse values by adjusting light blockers, changing the environment and camera position\settings. Anyone who is passed this scene on will have no troubles tweaking ti further. From another point, they use polariser fitlers to get rid of reflections, block lighting from producing speculars, spray with dulling or increasing specularity sprays, "paint with light" using long exposure to put the lightsource into the camera visible range but not visible in the final image, and even combine different exposures to make something like a collage. But not vice-versa. It looks like that there must be clearly defined workflow establishing what is more physically correct and less, and work from there.
Quality (imo) cheats:
by changing the light position and size of the lightsources
light blocking using gobos and adjusting the environment
managing reflections using gobos, camera position and environment
light diffusion using translucent, reflective planes(any substitutes imo are ok, like using mapped planes)
Those cheats are a bit "cheap" in cg:
light blocking using including\excluding from light
increasing\decreasing reflectivity of shaders even if you know it's correct
tweaking the diffuse even if you know it's quite balanced
turning off "visible to camera"(though "painting with light" technique can use lighting of a source withing the camera view, but it's not visible due to long exposure, but for stills)
Many people are interested in "unbiased" renderer Maxwell. I didn't use it, but from what I know it limits you to real life setups.
Probably using only cg tricks or completely omitting them in lighting is wrong, both are the extremes. Cg tricks are quite often possible in photography as photographers exist for a long time and developed their own arsenal of tricks to be free in artistic choices (up to retouching). But let's work from the ground up:
breaking physical laws is wrong. Those have been discussed already, but I will revise and reorganise the information soon.
If you can keep the physically correct route, keep it, but if you inevitably (debatable) need to hack, you can either:
use cg techniques
use photography hack techniques
Both require knowledge and experience, and perhaps only experience can tell what is more appropriate. But knowing both ways is a plus.