Excellent, thank you! Looking over the figures I think this has the necessary info for calculating optimal sun exposure length, inputting skin tone, latitude, and month. Sadly, it doesn't weigh dietary vitamin D against sun exposure or factor in the non-vitamin D stuff (I suspect the nitric oxide stuff and circadian regulation is pretty important), but still!

If If I sufficiently understand this then once I have more time I will try to give back by making an info-graphic which is more accessible to the public.

Judging from what I'm seeing here I think there might be benefit to timing when one's skin personally begins to "redden". I wonder if "darkening" is the same as "reddening". (I'm north-Indian dark and start getting tan lines with only 10 minutes of sun, which disappear within a 1-2 hours of shade. I'm not sure if that's analogous to the "skin reddening" they describe or if the skin reddening is a separate process indicating damage rather than melanin production. I've never actually gotten sunburn so I'm not sure when darkening ends and reddening begins, if it is indeed separate)