The visual filter (NetCam with the head mounted display) allows the feedback loop to be closed, so that I can see the quality of the images while they are being created. I also have some wearable light sources so that I can control the characteristics of the light while I watch the images through the HMD. Therefore, for example, it is never necessary to have people remove their eyeglasses, because I can dynamically adjust the position of light sources to control the reflection in the glass.
Because of the instant feedback, I can also be more adventurous with the lighting, and still maintain control over it. Other people I've made instant portraits for (manipulating light sources while looking at live video) include Baback Moghaddam, Matt Krom, Ron Newman, and Jennifer Healey.