I recently purchased a HN-1 hood to be used on a 28mm lense that I have. I like to keep the hood on the lense all the time, even when I change the filter. So my plan is to screw the hood on the lense directly and filter on the hood. It look like there are two places I can screw the filter on the hood, the smaller ring where I screw the hood on to the lense, and the place where I will have the 72mm lense cap on. Does anyone know the size of the smaller one? Do I sacrify IQ by this setup? I know normally people have the filter on the lense first then the hood on the filter. If not, should I go with bigger or smaller filter? Which way reduce the chance of vignette more? The primary filter I am using is polarizer. Thanks for any advice.