The various portions of a material definition all add up to the surface response to the lighting in the scene. In order to present a realistic look – to any extend – one has to balance the contributions of those portions to each other, and to the various kinds of lighting in the scene. See the short answer and an elaboration on this.
Next to that, all those portions of a material definition just add up mathematically, on a per-color basis. So RGB (80%, 60%, 15%) + RGB (60%, 50%, 10%) = (140%, 110%, 25%). This may cause overlighting (any value >100%) from
= Diffuse * all direct and indirect diffuse lighting + Specular * all (direct) specular lighting + Reflection * all light from other objects in the scene + Ambient + Translucence (both representing glow from the object itself)
I can dim the light (which will make the ambient glow look stronger) or I can dim all material aspects proportionally. This latter will darken the image (which can be corrected for in post, using Photoshop or GIMP or alike) but at least will avoid the clipping effects. Note that applying Gamma Correction (GC) automagically caters for some darkening, overlight reduction and re-brightening and should be used when possible. GC is available from Poser 10 on, and from Poser Pro 2010 on.
For instance, assuming all colors to be white so we’ve got to consider intensities and brightnesses only, say a light producing 90% diffuse and 80% specular light shines on an object having
- 80% diffuse
- 20% specular
- 20% ambient
This will produce 90% x 80% = 72% in the diffuse channel, plus 80% x 20% = 16% in the specular channel, plus 20% in the ambient channel, equals 72 + 16 + 20 = 108% which will get clipped down to 100% when presenting the result.
But do note
- That addressing diffuse and specular lighting separately requires the Advanced interface to the material room, using the color swatches for both
- Setting the intensities for Diffuse, Specular and Ambient can be done via the Simple interface, as well as via the Advanced interface, using the appropriate color swatches
- All color swatches for light and material will get affected by the Gamma Correction (GC) mechanism while rendering, which reduces the overlighting effect by itself. GC is available in Poser from version 10 up, and in Poser Pro from version 2010 and up. See further articles on its use, and on details.
- Setting the intensities for Diffuse, Specular and Ambient can be done via the Advanced interface, using the appropriate value dials. These are not affected by the GC mechanism, and hence will produce a different result from dimming the color swatches.