I've seen this number given before but I have literally never seen someone get a sunburn through a t-shirt. I've seen plenty of people with awful, terrible, red, peeling burns that required a trip to urgent care on their arms, and their torso is completely fine because they had a tshirt on. Is SPF 7 really all that's required? I usually use SPF30 sunscreen but it seems like that's overkill by a significant amount.
edit: UPF vs SPF is a distinction I hadn't made before I guess. Is the difference in effectiveness that large? Does traditional sunscreen offer UVB protection also, but it's not advertised?
edit: UPF vs SPF is a distinction I hadn't made before I guess. Is the difference in effectiveness that large? Does traditional sunscreen offer UVB protection also, but it's not advertised?