can´t see any difference in Texture resolution...

[Komposer]

hi,
the whole time, I´m using vray, again and again I tried to understand, what the Texture resolution in the vray lights mean or makes!
I red the manual, but it doens´t help me - no difference to see.
The two images shows a mirror plane, without any blurring.
A dome light with a 10000x5000 HDRI texture as dome Tex.
No filters in the file loader.
When I set the res to 50!!!! it looks identical, if I set the res to 10000! - see the both screenshot...
Can anyone explane me please, what this option do and for what I could need it, in which case it makes sense to input other than 512?
Thanks, Jörg
Maya2015, Win10

[vlado]

This option determines the size of a look-up table that V-Ray uses when it calculates lighting from the dome light on other objects. You will not be able to see any difference when observing the dome light directly, but the difference should be visible as different amounts of noise in the shadows of the dome light.

You'll have to adjust the default value very rarely - typically only when your HDR has very small bright spots that are causing noise.

Best regards,
Vlado