So having an SPF of 50 increases a time 50 fold, which really puts things into perspective. Never leave the house around lunchtime without sunscreen.
<quote>
There is a popular misconception that SPF relates to time of solar exposure. For example, many consumers believe that, if they normally get sunburn in one hour, then an SPF 15 sunscreen allows them to stay in the sun 15 hours (i.e., 15 times longer) without getting sunburn. This is not true because SPF is not directly related to time of solar exposure but to amount of solar exposure. Although solar energy amount is related to solar exposure time, there are other factors that impact the amount of solar energy. For example, the intensity of the solar energy impacts the amount. The following exposures may result in the same amount of solar energy:
- one hour at 9:00 a.m.
- 15 minutes at 1:00 p.m.
</quote>
> It's a common misconception that speed determines how fast you get to your destination, but actually distance also matters. So speed does not reflect time to destination. Instead, speed lets consumers compare the level of relative quickness and that 60mph is quicker than 6mph.
Obviously we need to hold other factors constant. It's not a useful point in when talking about speed and I don't see the point in talking about SPF. And it certainly doesn't mean that time to destination is inversely proportional to speed.
Either way the multiplicative one is clear: 30 minutes of midday exposure with 30 SPF is approximately equal to 1 minute of midday exposure and so is minimal. That's helpful to know! And 50 is only moderately better than 30, but 30 is a lot better than 10 - the FDA page says nothing about this.
I merely want to provide a fuller explanation of what SPF is from an authoritative source, in this case the FDA.
As the article discusses it also depends on your skin. If you are a fair ginger then yeah, sunscreen is your life. If you are more swarthy then you can get away with some midday sun.
No you can't. Or rather, you shouldn't. If you have more melanin you obviously have more protection. But your skin will still get damaged by a midday sun, and it will age faster than normal.
This misconception that darker skin does not need protection is really harmful. Maybe that allows you to skip sunscreen for short periods of time, or in early morning, late evening. Not midday, unless "some sun" means just a few minutes.