What's the difference between these two? I'm browsing ebay and see both of them without much of a price difference. I have a Sony A-100 with lens diameters of 49mm (minolta 50 mm), 62mm (sony 10-200 mm), and 77mm (sigma 10-20 mm). I know I could simply hold the filter in front of the lens, but I'd like to have the holder because I don't have very steady hands and need both to hold the camera still. I'm wanting graduated ND filter as well as regular ND filters (are those the ones that tone down the brightness??). Anyway, thanks for clearing up the difference between the two types of filters! --------------------------- Nevermind...I found my answer here: http://www.geocities.com/cokinfiltersystem/howitworks.htm However, this site says the P series will work with lens up to 82mm diameter...but the image they show of the P series says the circle diameter is 74.3mm. How is that possible?