(See my image in p.b.i for a comparison of the two).

So, my question is, does someone need both?

I've been in the habit of using specular for my finishes, and I've only 
seen phong used a couple of times.  I know that they use slightly 
different formulas but, for artistic usage, is there any reason that I 
should choose one over the other?

Or, more interestingly, is there any reason I might want to mix them in 
the same scene (some objects using specular, and some using phong)?

Personally, I can't see there being an artistic difference between the 
two, and I really wouldn't miss the phong feature if it weren't in POV.

...Chambers

BTW, I don't know the specifics of the internal functions in POV, but I 
remember Phong being a really cool way of shading polygons in a scan 
line rasterizer.  Back in the '90s, the big thing for a while was 
Gouraud shading, which was used to interpolate color values between two 
points (and, later, interpolate the light values, and apply those to a 
texture map).  However, "Phong shading" was used to describe the process 
of interpolating the normals, and performing the lighting on a per-pixel 
basis.  Of course, since POV-Ray has always done full lighting 
calculations on a per-pixel basis, I think it must refer to a different 
algorithm :)

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