croftrobin Posted June 19, 2015 Share Posted June 19, 2015 I wear spectacles in Thailand that I bought in the UK. When I am in the UK, the lenses go quite dark in sunlight. However when I am in Thailand, they do not darken. A friend also has found the same with his spectacles. Why do they not darken here? Is it because the sun is more overhead? Link to comment Share on other sites More sharing options...
mesquite Posted June 19, 2015 Share Posted June 19, 2015 Probably. Link to comment Share on other sites More sharing options...
casualbiker Posted June 20, 2015 Share Posted June 20, 2015 (edited) Or the UV is actually to HIGH! I was wrong.. You were partially correct... Heat and height of the sun are factors! http://superbeefy.com/how-do-photochromic-glasses-work-and-why-do-photochromic-lenses-turn-darker-in-the-winter-than-in-summer/ Edited June 20, 2015 by casualbiker Link to comment Share on other sites More sharing options...
dbrenn Posted June 20, 2015 Share Posted June 20, 2015 I wear spectacles in Thailand that I bought in the UK. When I am in the UK, the lenses go quite dark in sunlight. However when I am in Thailand, they do not darken. A friend also has found the same with his spectacles. Why do they not darken here? Is it because the sun is more overhead? Photochromic lenses work better at low temperatures. Link to comment Share on other sites More sharing options...
lopburi3 Posted June 20, 2015 Share Posted June 20, 2015 As said heat is the reason - they do not work well in high temp - actually they do not work well anywhere in my opinion - a real danger driving through tunnels. Link to comment Share on other sites More sharing options...
i claudius Posted June 20, 2015 Share Posted June 20, 2015 mine work fine Link to comment Share on other sites More sharing options...
casualbiker Posted June 20, 2015 Share Posted June 20, 2015 mine work fine What brand.. I presume they work in Thailand! Link to comment Share on other sites More sharing options...
kevc Posted June 20, 2015 Share Posted June 20, 2015 I always buy photochromic lenses and work fine, get them from Modern Optical on Sukhumvit Link to comment Share on other sites More sharing options...
mesquite Posted June 20, 2015 Share Posted June 20, 2015 Hmm...I always wondered why they turned extremely dark when it had snowed. The reflected light off the snow hits the lens at a right angle, and of course it's cold. Mystery solved. Link to comment Share on other sites More sharing options...
zyphodb Posted June 21, 2015 Share Posted June 21, 2015 The ones I brought with me from the UK don't work here, but the ones that I bought here work fine, so maybe different grades of photochromic??? I dont know, just guessing... Link to comment Share on other sites More sharing options...
partington Posted June 21, 2015 Share Posted June 21, 2015 This is really interesting. I had no idea about photochromic lenses working less well in hot temperatures, so I've learnt something. I recently bought some photochromic glasses from Zenni optical, the online seller. I've bought many pairs of prescription glasses from them before, and they have been really excellent as well as one fifth or less of the price of high street suppliers here. But I was really disappointed with the photochromic lenses: going out into midday Bangkok they barely seemed to change, certainly not enough to reduce glare, in fact hardly enough to even be visible as a faint cosmetic tint. Useless as sunglasses. After reading this I put them in the fridge for 30 minutes, then left them on the window ledge in the sun. They shifted to a much darker shade than I have seen them achieve before- very nearly sunglass dark. So this is true. Doesn't help me much to use as sunglasses here but it's nice to know why! Link to comment Share on other sites More sharing options...
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