MarketDelta released a beta version today of MD Charts that has a new Footprint type called Imbalance Footprint. It automatically detects and shades high volume levels based on the bid and ask volumes. It uses a new methodology for comparing the bid and ask volumes to one another. Read more about it on the MarketDelta blog. I would recommend following the MD blog as well since they post things other than just Footprint related information. So far this seems like a very nice addition to the software and produces great insight and patterns to trade from.