While comparing the Glass material between YafaRay and LuxRender (which is a very accurate, although slow, physically spectral renderer) I've noticed that the Glass preset material in LuxRender seems more realistic than the same material with the same properties in YafaRay.
This is the LuxRender glass with a uniform white background and a filter=1.f, IOR=1.5f and reflection=0.7f (almost the default preset in LuxRender)
And this is the YafaRay glass with the same properties:
I found out that the YafaRay Glass material does not take into consideration the Reflection color for the Internal Total Reflection calculation. So, I've corrected it in the code, which will be available in the next YafaRay version:
With the change, this is how the same material looks like in YafaRay:
I hope this will allow us to get a more realistic glass in YafaRay from now on.
The example scene is in the next comment.