I was shooting at an outdoor sports event a couple of weeks ago and it was such a bright day that at ISO100 I could not use f2.8 even with maximum shutter speed. I moved out to f4/f5.6 but it made me think I need to get an ND filter of some sort for this situation. I was using a D5 and I could have gone down to a LO ISO but I haven't used these settings before so wasn't sure whether it would impact image quality. Obviously I can (and will!) experiment but I thought I'd ask here for advice about best approaches. It also made me think I should get a polarising filter as that would add at least one stop and improve the sky colour on days like that. Any advice/suggestions ? Thanks.