You can use the DMC sampler as global quality control, for example:
For lower quality:
- increase the Adaptive Amount
- increase Adaptive Threshold
- reduce Adaptive Min samples
For higher quality:
- decrease the Adaptive Amount
- decrease Adaptive Threshold
- increase Adaptive Min samples
These controls have effect on everything: DOF, GI, glossy stuff, area lights etc.
Color mapping mode also affects render times and sampling quality, since V-Ray tries to distribute samples based on the final image result.
The images below have the same subdivs for DOF (10 subdivs), GI (50 subdivs, Direct method), glossy reflection (50 subdivs, no interpolation), area light (10 subdivs) for all images. Notice how changes in the DMC sampler parameters affect the image quality and render time (click the images to enlarge them):
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Settings
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Render time
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Amount
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Threshold
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Min samples
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 |
0.85
|
0.005
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15
|
2m 3.9s
|
 |
0.95
|
0.01
|
5
|
0m 53.6s
|
 |
0.95
|
0.05
|
5
|
0m 25.5s
|
 |
0.99
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0.05
|
5
|
0m 22.8s
|
 |
1.0
|
0.1
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5
|
0m 28.6s
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