In case anyone has followed this video by The Letter Is B

about how to properly do a green screen, he suggests using Chroma Blur as the very first effect in the chain. When I initially followed these steps, I could not see any effect of the chroma blur at all and actually wondered if the plug-in was broken. Then when I looked at it much closer, I realized it has an extremely subtle effect on smoothing out the some edges of the mask. I am still not sure why you would use it over the Blur in the Chroma Key Fx, other than it is perhaps even more subtle?? The place I notice the effect the most is on the corner of her left shoulder and the legs, but other than that, it doesn't really jump out at me.

Any way, this is a pic with the Chroma Blur on Maximum blur compared to No Blur at all. And that's 4.0 max on vertical and horizontal pixels.

Also, in adding to this, the video recommends applying the Chroma Blur first, then the Chroma Key second. But in the couple of tests I've done, I seem to get better results with applying the Chroma Key first, then the blur. I've always done the key first, then add blurs and other effects to improve the mask after that. Not sure what others think about this. But here's a screen shot. I notice there seems to be more green spill or contamination when the blur is applied first, especially around her feet. The Chroma Blur in the below pic is set to Light Blur Preset.