The goal of Lambda parameter is to remove the exponential decay (slope of the entire recording) of the photometry signal that arises due to photobleaching and obtain a nice flat DF/F trace. The lambda value is used to find the shape of this slope. Ideally, the displayed fitting line should nicely trace this exponential decay without picking up small fluctuations (and especially do not pick up real peaks in the data), as it will remove real signal!).
