Min and Max sub in Adaptive QMC (beginner problem)

[marionikolovski]

Hey

I'm new here so I apologize if this has been posted before but I haven't found anything regarding this subject.

 

I've been reading "VRay The Complete Guide 2nd edition" by Francesco Legrenzi and I've come up to a part where he does render tests using the Adaptive QMC.

 

In one of the examples where there is applied DOF and Reflection, when the Min Sub = 1 and Max Sub = 50, it appears that there is more noise on the final render than if the Min Sub = 1 and the Max Sub = 4. In short, the quality of the image appears better if less Max Sub are used. The color/noise threshold remains unchanged. The render times are also bigger if less Max Sub are used.

 

I'm relatively new user of VRay, but from my understanding, setting a bigger number for the Max Sub should allow VRay to use more samples for calculating, if it determines that it should depending on the color/noise threshold. Surely in some instances, VRay might determine that it should use 16 or above 16 samples for certain pixels if the Max Sub = 50, but it cannot go above 16 samples per pixel if the Max Sub are set to 4. So how come VRay outputs an image with more noise if it uses Max Sub = 50 than if it uses Max Sub = 4? Shouldn't the final output be better or at least the same if Max Sub = 50?

 

Maybe I have a misunderstanding on how the Min and Max Sub parameters work so I hope that someone here could clarify and explain this (and I hope I explained it well).

 

P.S The examples are on page 176 for those who have it.

[wojciechsokalski]

Read this:

http://www.cggallery.com/tutorials/vray_optimization/

 

For me, it's the best explenation of how sampling works.

You can also watch this (real example of what's described in above article):