Hi. I have a Pentax K50 with a 300mm Tamron telephoto lense. I've been able to take amazing pics of my daughters playing outdoor sports (lacrosse and soccer) on the "sports" setting but indoors for gymnastics the pics are all grainy. I suspect it has something to do with lighting but I need some help. What would I change to get good crisp action photos in indoor settings with typical fluorescent gym lighting?