> The study you link states that 'To prevent vitamin D deficiency, one should spend 15 to 20 minutes daily in the sunshine with 40% of the skin surface exposed.'. The screenshot on lume health shows a goal of 120 minutes.
Linearly it follows that if one wears clothes that cover more than 40% of lit skin, then the duration would be adjusted to match the total skin-area/time.
If one start with 1.85 m^2 body surface area, 40% of that is .72 m^2. If clothing covers 50% of a human and the human's shape and hair occludes half of that remaining, you have .46 m^2 available for sunlight. .72 m^2 * 20 is 14.4 m^2/min. divided by .46 m^2 it seems that 31.3 min would be the daily amount.
This seems much less than lume health's goal of 120 min. Otoh, given there is less opportunity for get to 14.4 m^2/min daily (I'm looking outside at a nice rainstorm), maybe the 120 min has some catchup factor?
Linearly it follows that if one wears clothes that cover more than 40% of lit skin, then the duration would be adjusted to match the total skin-area/time.
If one start with 1.85 m^2 body surface area, 40% of that is .72 m^2. If clothing covers 50% of a human and the human's shape and hair occludes half of that remaining, you have .46 m^2 available for sunlight. .72 m^2 * 20 is 14.4 m^2/min. divided by .46 m^2 it seems that 31.3 min would be the daily amount.
This seems much less than lume health's goal of 120 min. Otoh, given there is less opportunity for get to 14.4 m^2/min daily (I'm looking outside at a nice rainstorm), maybe the 120 min has some catchup factor?