3 ms·
You can't compare the straight percentage, a 98% filter lets through twice as much as a 99% filter.
by andreareina 1y ago
You can't compare the straight percentage, a 98% filter lets through twice as much as a 99% filter.
- Nursie 1y agoTrue, so the important factor is - how does this map to your chances of getting skin-cancer?
- DoctorOetker 1y agoThe most reasonable answer is to look at the transmission percentage, not the blocking percentage.
- aydyn 1y agoNo it isnt. Two photons is twice as much transmission than one photon, but both cases are totally insignificant.
- jandrewrogers 1y agoIn both cases though the level of UV will be easily tolerated, which is the entire point. UV index is a linear scale, so more SPF has rapidly diminishing returns even in places with a UV index of 15+. That the duration of protection is independent of SPF makes this particularly true. There are only a handful of places in the world where atmospheric conditions might give a very high SPF marginal benefits.
- Thaxll 1y agoHow? Sorry I'm confused by that statement.
- daemonologist 1y agoIf you have a "100 unit" light bulb, and a material that blocks 98% of the light it emits, 2 units of light are getting through. If you have a material that blocks 99% of the light, only 1 unit - half as much - is getting through. (This is why the SPF scale is inverted/measures transmittance. SPF 50 sunscreen theoretically allows through 1/50th of the UVB radiation (or whatever wavelengths are specified by your local regulator).)
- rrsp 1y ago98% = 2 units of UV reaching the skin 99% = 1 unit of UV reaching the skin Thus 98% filtering lets in 2x as much as 99% filtering