I think I'm going to have to use different kinds of ND filter on my Polaroid SX-70 for different situations, i.e. ND2 for indoor and ND3 for outdoor because using ND3 indoor makes for some underexposed Polaroid shots. Thank the Flying Spaghetti Monster for free filter samplers. If you ever need some ND filters for your Polaroid SX-70, I'd highly recommend getting the Lee Filters Cinematographer's Edition swatch book that you can order through their contact form for free. It sure beats ordering a tiny piece of overpriced ND filter from Hong Kong, which I wish I could say I hadn't done before.