Ok, i'm sort of realizing how stupid this is. I better pull out by Astronomical Photometry book... On Sunday, June 9, 2002, at 06:05 PM, Michael Koppelman wrote: > I want to explain my assumption: > > Unfiltered = B + V + R + I +/- overlap or gaps, no? > > How could unfiltered get less signal than if I had an Ic filter on?