Originally Posted by Eric Pascarelli
Just a quick curmudgeonly correction - it's actually less depth of field that's achieved by opening the iris.
Depth of field refers to the depth of what is in focus in your scene. Greater depth of field means that more of scene is in focus, and this is achieved by closing down the iris.
What Geoff was saying was that sometimes you can prefer to have TLCS preserve the stopped down iris, adding gain to obtain correct exposure before the iris is fully opened. That's where the greater depth of field would come from that he is referring to.