https://cdnmedia.eurofins.com/apac/media/609921/spf-iso-protocol.pdf https://cdnmedia.eurofins.com/apac/media/609921/spf-iso-prot... That's my entire point. Th

https://cdnmedia.eurofins.com/apac/media/609921/spf-iso-protocol.pdf https://cdnmedia.eurofins.com/apac/media/609921/spf-iso-prot... That's my entire point. The way they generate SPF measures how much of the sun it blocks in the lab shortly after it's applied. That one blocks 97.5% and another 98% is meaningless for the real world.