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I like to wear sunglasses when the sun is very bright. The trouble is when I am riding quite often I bike into shaded areas or under bridges. This happens so fast sometimes I don't get the sunglasses off and then it is so dark I can't really see what I am riding on or going. Sometimes there is a big bump, something on the trail, a big puddle I'd rather not go through, etc.
So what do you do???
There are a number of photochromic and light-adaptive lenses for use in different types/changing light. Nanotechnology has made increasingly better changes in that. (Here) is a look at different types/colors of lenses and uses.
If you're talking about really bright to quickly really dark then i just quickly pull my glasses off since i use chums on them and they'll just hang. I use a different type/colored lens depending on what the days ride light is going to be since it’s a quick and easy change with one pair of my riding glasses…Oakley's with prizm lenses are my most used and versatile ones for rides. For my eyes they work well for contrast and clarity in seeing road surface changes especially on days with a mix of cloudy and sunny skies and from sun to mountain shady treed sections especially on descents…. the downside is price but mine also are well made and fit me really well so they’re worth it for me. I also use gray lenses when in bright desert sun and yellow for dawn/dusk commutes. What works for me may not for you though so trying different colors/types is probably the best way to find something that works for you. Perhaps go to REI, lbs etc. and try some different ones.
eta..a work colleague and mountain biker said she really likes trail prizm's for the continual clarity going from light to shade and for seeing roots/rocks etc. on a trail.
Slow down?
It sure is a temptation to keep barreling through dappled light. It nearly ended badly for me when a deer crossed near me on a fast, fun descent.
Just as in a car or motorcycle at night - or when cresting a blind hill or taking a blind corner - the limiting factor on your speed needs to be, if something happens just beyond what I can see at this moment, will I be able to respond to it in time? That's partly about limiting speed, partly about heightening awareness, partly about developing skills. There's a classic article about this in motorcycling called "The Fridge Factor" - the gist of which is to ride as though just beyond the apex of that turn, in one lane there's a refrigerator, and in the other lane there's the pickup truck out of which the fridge just fell. It applies equally to any road user.
It's been a long time since I wore light-sensitive lenses, but I don't think they respond instantaneously even now. I'll totally take my glasses off when needed - or in the evenings, swap to a pair of amber lenses - but you don't want to be taking a hand off the bar and fumbling around in your jersey pocket in a critical situation.
I got sick of changing the lenses, so I bought a pair of super dark cycling sun glasses, and kept the frames from my old pairs (thank you, Performance Bike). I have 3 pairs, dark, amber, and clear. My suggestion is to wear the amber ones if the shady areas bother you. That way, you'll have some glare protection, and it won't be too dark in the shade. Myself, i prefer very dark lenses, and the shade isn't an issue for me. My issue is when I start a ride at dawn and it is dark, wearing clear lenses, and then the sun rises. If the ride will be longer, I stick my dark lens pair in my jersey pocket.
I have light sensitive lenses in my progressives, which I never wear cycling (I wear contacts with sunglasses). They take a loooong time to change and it drives me nuts. The old photo gray lenses changed almost instantly.
I have photochromic prescription lenses...I like them for wearing under any lighting conditions, as they go from REALLY clear to REALLY dark...but it takes probably at least 30 minutes for them to go from dark to clear. I've had faster ones, but they didn't have such a wide light/dark range.
I'm not sure there is a good eyewear solution for the scenarios you're describing, unfortunately.
If someone doesn't have a lot of eye sensitivity to light they should be able to find a transition range that works quickly for sun to shade. My eyes aren’t light sensitive so my usual riding lenses don’t go to completely dark nor clear either and I don’t notice any time lapse in clarity in the average type of temperature, sun and shade on my rides…with the exception of strong desert sunlight riding where I switch to darker lenses.....but yes if the lens is really dark from bright light going into a really dark area the best way is probably using a sunglasses retainer strap like chum etc. so you can just quickly pull them off and get your hand back on the handlebar.Quote:
Originally Posted by zoom-zoom
Work on molecule chemical reaction is continuing to give faster transitions and longer life for plastic photochromic lenses. Depending on how the plastic, dyes and molecular engineering are done and the transition range it can take from instantly (more expensive to create) to seconds or to minutes to make a change. Hot/cold temperatures also factor in. Glass photochromic lenses can take much longer to change because of the silver halide crystals....plastic photochromatic with cheaper and easier to use naphthopyran molecules too.