I think the green (X1) filter is just about useless. With an ASA 400 speed film on an overcast day, which is the best kind of weather for portraits IMHO, will give you about 250 at f4-5.6. With the green filter you've lost 2 stops and if you have a 105 f2.5 lens you're going to have to shoot wide open. That's not conductive to the best quality over stopping down a couple of stops. I wouldn't want to shoot with that lens under 250 to be assured of a sharp photo. Anyone else run into this?