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Recommend an ND 1.2 for normal sunny days. Should allow you to achieve your 5.6 aperture on a 12mm or 15mm lens with a 30fps and 1/60 shutter... may need to adjust your aperture up or down a bit.. but should be close. Recommend getting a ND 0.6 as well... I have ND 0.3, 0.6, 0.9, and 1.2... But if I were only getting two, I would get a 0.6 and 1.2. You will want to get the 46mm size with the X5S. Instead of using a ring balancer with a 46mm lens, use a step up adapter (37mm->46mm) instead. Using the step up adapter with the weight of one of these ND filters, will give the proper balance. It will also allow you to use your existing 46mm ND filters.