Example 1: Noise vs Speed

 

Example 1: Noise vs Speed

You can use the DMC sampler as global quality control, for example:

 

For lower quality:

 

For higher quality:

 

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):

 

Settings
Render time
 
Amount
Noise
Min samples
0.85
0.005
15
8m 43.7s
0.95
0.01
5
4m 34.5s
0.95
0.05
5
1m 35.8s
0.99
0.05
5
0m 49s
1.0
0.1
5
0m 28.6s