In the summer, there is always an increase in advertisements and public awareness campaigns to get people to wear suntan lotion, to reduce the risk of sunburn (naturally).
Some of these advertisements often say that it is still possible to get a suntan while wearing suntan lotion, presumably to encourage those with higher resistances to the sunrays (or those that are consious of the way they look) to still where sun lotion.
How can this be true? If you are being protected from sunburn, surely you are also protected from suntans? My understanding is that a suntan is just underdeveloped sunburn - likewise, sunburn is over exposed suntan, both being caused by the same exposure to the same UV rays. Is this not correct? If it is, how can protection from sunburn not also protect you from sun tans?