Are you hoping to get a burn or tan? It is important to protect your skin, even if you don't get a burn- with fair skin especially, you risk skin cancer by not protecting your skin.
As far as vitamin D absorption, if you are having trouble you may want to make sure that you are eating foods/taking vitamins with magnesium in them, which should help you absorb the vitamin D better. If that doesn't seem to be too low, there are many other factors that you can address that can help absorb vitamin D better- things like weight and checking on the health of your liver and kidneys to make sure they are functioning correctly. It's also good to note that wearing sunscreen doesn't prevent your body from absorbing Vitamin D, studies have shown that those who wear it and those who don't have virtually the same level.