I use a number of Gary Fong products, including the Lightsphere. I use the collapsible model when traveling. What this lesson shows is how color balance is achieved. You take a picture with the blue gel over your lens and then set your custom white balance to that image. Put the blue gel on your lightsphere (or speedlight) and snap. What you end up with is a color tone at the opposite end of the spectrum. For blue, it’s red. For green, it’s magenta, etc. Off to practice!