 Poster: A snowHead
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I can buy the fact that clearly I am not going to see when there is thick mist. What I would like to understand is, scientifically, why is it so difficult to see in 'flat light' when the conditions may otherwise be fairly clear from a precipitation perspective. Why does the light go 'flat' - can someone give me a physics lesson? B.t.w. I hate both mist and flat-light, anything that means I can't see where I'm going I don't like.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Megamum, flat light, which may happen when it's cloudy, or when the sun disappears behind a mountain at the end of the day, causes a lack of definition between sunny and shaded areas and changes in the contours of the piste disappear due to the lack of shadow.
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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Megamum, I think its when the sky is totally covered with snow bearing clouds so that the illumination levels both from the sky above, and the reflecting snow covered ground below are nearly uniform ie totally diffuse lighting. In this case, there is virtually no contrast levels between different parts of the ground, making it impossible to see the horizon or to discern differences in nearby ground texture (both of which factors make you lose your balance and make it a b*gger to just ski at all).
Just my 2p worth.
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Has something to do with the clouds reflecting too much light from the blue wavelength, which the human eye struggles with because of the way it scatters. Which is why yellow lenses work well in flat light because they filter out the blue.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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You'll need to Register first of course.
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The biggest problem is the amount of light.
When light is described as 'flat' there is hardly any of it. You can still see but there is probably only 20% of the light there would be on a cloudless day. Also, because the sun's rays are not being reflected from a uniform ray angle (they are being reflected from the light that makes it through an entire sky full of cloud), contours are not defined. The back side of a dip is as illuminated as the front side so the dip isn't defined by shadow or a reduced whiteness.
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All the cloud diffuses and scatters the light so much that shadows become almost nonexisitant since the light is appears to be coming from pretty much everywhere and has no real direction. With no shadows it's impossible to make out bumps and depressions since shadows are how we see the form of something; this is why goggles for poor light are orange since this increases contrast by filtering out blue.
Last edited by Then you can post your own questions or snow reports... on Tue 5-10-10 11:54; edited 1 time in total
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+1 for narc's explanation - simple and accurate
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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These explanations miss the obvious, fundamental point, which is that the physics that really matters in this case is gravity: flat light makes you fall over, no?
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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| Megamum wrote: |
| I can buy the fact that clearly I am not going to see when there is thick mist. What I would like to understand is, scientifically, why is it so difficult to see in 'flat light' when the conditions may otherwise be fairly clear from a precipitation perspective. Why does the light go 'flat' - can someone give me a physics lesson? B.t.w. I hate both mist and flat-light, anything that means I can't see where I'm going I don't like. |
You did ask 
OK then a little (just a bit) of science –
The sun is made of lots of stuff and it’s quite big – ok with me up to now?
As the sun is so big it bends time and space near to it (yea – trekkies are happy now) making stuff move towards it’s centre – obviously other stuff is also bending time and space as well, so there is an inter-reaction between all bending and well lets just say that all the stuff (and I do mean “all” stuff) flies around on it’s own happy course. So we’ve got that. The force know as gravity (regardless of what you’ll wiki-read or some  who will be along to in a minute will tell you) doesn’t really exist but it is just an effect on (and caused by) the bending time and space. Phew, heavy or what.
So (getting back to the sun) some of the stuff (that the sun is made of) follows a course that is dictated by the bending of time and space. But as there is nothing near enough to stop this stuff heading off down towards the middle of the sun – so that’s where it tries to go, but as everything else in the sun is also trying to head in the same direction you get a bit of a squeeze down there. There nearer to the middle you get, the squashier it gets. Lots and lots of stuff trying to squeeze into the same space.
Next, the sun is made up of lots of weird stuff. Some of it is hydrogen. Now you have to remember that lots of this hydrogen is whizzing it’s way down towards the middle of the sun so sooner or later it’s going to bump into more hydrogen doing exactly the same thing. On and on this goes with more and more hydrogen trying to squeeze into a smaller and smaller area. Well – this ain’t too good for the hydrogen, as eventually it’ll get so squashed together with other hydrogen that the 2 bits will merge together and (hey presto) it transforms into Helium.
Now here’s a weird thing. There is not as many “bits” needed to make one bit of Helium as there were in the 2 bits of Hydrogen. So (I hear you ask) what happens to the bits that weren’t needed. Well let’s just say it all goes Bang, in a big way. This extra stuff flies off in all directions some as other weird little bits of stuff and some as energy like x-rays, light, radio waves, etc, etc (lots of etc’s and there lots of types of this energy).
Some time (only a few minutes) later some of this energy may hit something and some of it will bounce off and go flying off in another direction. Some of this may then hit your eye ball and if it’s the right type of energy some strange bits in your eye will convert this energy into an impulse that travels along a nerve and into your brain. Hey presto!, you have just seen something.
Lets move back a little and look at the different types of energy and split it into two types. The energy you can see and all the rest that you can’t. Here we are only interest in the energy you can see.
For various reasons this energy (I’ll call it light from now on) is measured in wavelengths – don’t ask why, it’s complex and hurts my head. If you think about it like a long bit of string that, when you shake one end, will wobble, like a wave on the sea. Next count the number of wobbles per second and we’ll call that the wave length – the time between each wobble. The difference in time between each wobble will determine which colour your brain will imagine when your eyeball in hit by the light. Yeah I know, way too complex for me as well. Anyway if the wavelength is slow you see Red, a little faster and you’ll see orange then yellow blue and for really really fast wobble you get indigo and violet.
So Blue has a really high wavelength – that’s the time between one wobble and the next. So (important bit here) it’s smaller than most of the other light than you can see. As it’s smaller it will reflect of smaller stuff – like the molecules in the air or snow flakes or water droplets in the air, or even atoms, etc. I’m not saying that other colures don’t reflect, just that the higher wavelengths (like blue) will reflect / scatter more off these small bits of stuff.
So when there are lots of small bits around, like when you’re in a cloud, the blue section of light will tend to bounce around / scatter more.
When you’re skiing in cloud this is known as Flat Light as there is so much blue bouncing around it tends to “take over” and make it difficult to see the other colours. This combined with the fact the cloud itself is blocking most of the light (which we need to see) means that it’s difficult to ski around as we would normally due to the reduce visibility.
This is the reason that ski goggle try and block out some of the blues part of the light. As always it’s not as simple as it may seem. This is also the reason that ski goggles tend to be yellow or orange or rose, which, again ain’t as simple as you’d think.
To get your (and my) head around this we need to look at how and what you actually see.
Most people have just three colour receptors at the back of their eye ball. These are designed to see either Red Green or Blue. – like the screen you’re looking at now, eg. RGB. So if you see a Green ball it’s because the surface of the ball has absorbed all the colours except green – which has been reflected into your eye. So a Yellow filter on a set of goggles will, as yellow is just a combination of Red and Green, absorb all other colours and reflect (or allow through) just the red and green as the blue has been absorbed. And, as we learn above, as the blue is bouncing around more off the stuff in the clouds it is this that is making it hard to see. If we reduce the amount of blue reaching our eyes we should be able to see better.
So for flat light you need
Some light
Lots of small bit of stuff floating around (like a cloud)
Some yellow or orange goggles
A good place to go and have a drink until things get better.
PS
It’s got nowt to do with shadows – that’s to do with perception and not flat light
Last edited by snowHeads are a friendly bunch. on Mon 4-10-10 19:33; edited 1 time in total
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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Wayne, I like your explanation. Though, I said the same thing in two sentences (without the nuclear reaction stuff, of course) 
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Wayne, Ooooo..........that puts the cat amongst the pigeons, not so much to do with shadows as with blue light bouncing round. Any other takers?
So I've got a pair of Goggles with a Scott amplifier black chrome lens and a pair with Oakley VR50 pink iridium lenses I've so far tested neither - which will be best in flat light?
Agree about requirement for a good place to go for a drink until things improve.
Also, agree about flat light seeming to increase gravity and pull you over.
Any more suggestions as to how to counter-act the effect - the more scientifically proven the better as this is an interesting thread so far.
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You know it makes sense.
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megamum, concentrate on your other senses when the light goes flat - and make sure you're balanced over your feet. Coping with - indeed, enjoying - such conditions is what your lessons are for. 
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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laundryman, +1
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Poster: A snowHead
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just relax and believe you can ski and you will not have a problem with ' flat light '
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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The intensity of scattered radiation is inversley proportional to the power of the fourth wavelength.
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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| Megamum wrote: |
| Any more suggestions as to how to counter-act the effect - the more scientifically proven the better as this is an interesting thread so far. |
It's really simple.
The best way to deal with Flat Light is to be a good person all of the previous year prior to going skiing
and then, of course, the sun will shine on you always (inc. whilst you're skiing)
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You need to Login to know who's really who.
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Ski with your eyes closed, you won't ever fall over in "flat light"!
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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abc, I know it's a useful exercise to do, but it really does my fear factor no good at all. Those blind people that ski with a buddy have got guts I'd never have, mind you I bet they don't have problems with flat light.
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You'll need to Register first of course.
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Megamum, Wayne, Point of order peeps - no such thing as high wavelength . Wavelength (distance between peaks in the wave - or troughs) is long or short, frequency (number of waves in a given time) is high or low. Blue light has a short wavelength and a high frequency. Other than that, can't fault the explanations so far. 
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Wayne,
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| The force know as gravity (regardless of what you’ll wiki-read or some who will be along to in a minute will tell you) doesn’t really exist but it is just an effect on (and caused by) the bending time and space. |
So for the past 30 years the whole of the theoretical physics community, who have been trying to unify quantum theory with gravity, have been wasting their time?
Who's gonna tell'em?
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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| Megamum wrote: |
| I can buy the fact that clearly I am not going to see when there is thick mist. What I would like to understand is, scientifically, why is it so difficult to see in 'flat light' when the conditions may otherwise be fairly clear from a precipitation perspective. Why does the light go 'flat' - can someone give me a physics lesson? B.t.w. I hate both mist and flat-light, anything that means I can't see where I'm going I don't like. |
The clouds roll in.
They cover up the sun.
It goes darker.
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| Whitegold wrote: |
| Megamum wrote: |
| I can buy the fact that clearly I am not going to see when there is thick mist. What I would like to understand is, scientifically, why is it so difficult to see in 'flat light' when the conditions may otherwise be fairly clear from a precipitation perspective. Why does the light go 'flat' - can someone give me a physics lesson? B.t.w. I hate both mist and flat-light, anything that means I can't see where I'm going I don't like. |
The clouds roll in.
They cover up the sun.
It goes darker. |
I HATE physics but even I understand this explanation.
You are, IMHO, a genius!
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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It is the most strange optical effect I've so far encountered though. You stand there and one minute you can see where you want to ski and the next it just vanishes. Even if I struggle to 'see' what I've seen before it's just not there. It's just so weird. Maybe someone needs to design a set of goggles that projects a pattern of red dots onto the ski slope in front of you to convince you its still there.
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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Megamum, I spent 30 hours climbing and getting down in a storm (the top of Caingorm is not a nice place to do an enforced bivi - 10 hours of extreme BRRRRRRR). Most of the time we were in the proverbial ping pong ball, had to stay roped up even when walking as we couldn't even see each other once 20 feet away.
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You know it makes sense.
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Scarpa, that sounds.....errr.......interesting  When you think about it modern science should be able to solve the problem. After all we put a man on the moon 40 odd years ago, yet there is still not available a cost effective solution to flat light. We often get these students asking us what they should do their college work on we should suggest that they come up with with a solution to flat light that the average rec. skier can afford.
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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Megamum, why do you think flat light needs a "solution"? Don't the variations of terrain, snow quality and atmospheric conditions provide the infinite variety that keep most coming back for more?
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Poster: A snowHead
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| Megamum wrote: |
| I hate both mist and flat-light, anything that means I can't see where I'm going I don't like. |
Stop, close your eyes.....what do you see?......open them again....you can see so much more.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Just attach a powerful torch to the front of each of your skis. Simples.
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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| Megamum wrote: |
| After all we put a man on the moon 40 odd years ago, yet there is still not available a cost effective solution to flat light. |
First, as Spyderman pointed out, flat light isn't neccessarily a "problem" needed to be solved.
Second, there's physics, as your own thread title indicates. You might as well ask, why haven't we found a solution to people who are blind to be able to see! Physics dictates when there's no light, you can't see. And when there's no directional light and no color, your brain isn't developed enough to inteprete the different objects your eyes are seeing!
Third, solutions may exist. But when you add "cost effective", it raises the bar further to a new height.
The question becomes, how do you make something that isn't even neccessary (#1) cost effective (#3)?
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You need to Login to know who's really who.
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Megamum, I think what they are saying is MTFU
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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| Quote: |
but even I understand this explanation.
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it's simple, but wrong. Not every cloudy day produces "flat light".
JimW,
Megamum, you know my prescription for less-than-perfect conditions already. Get some good rhythmic music going, relax, get in the frame of mind of a snowboarder who's just had a spliff (or maybe better still, have one) and avoid unknown difficult slopes. And MTFU.
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You'll need to Register first of course.
You'll need to Register first of course.
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| Megamum wrote: |
| We often get these students asking us what they should do their college work on we should suggest that they come up with with a solution to flat light that the average rec. skier can afford. |
That'll be these then.
We look forward to seeing your new military look on the piste this year Megamum
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Is 'physics' singular or plural ?
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| rayscoops wrote: |
| Is 'physics' singular or plural ? |
Physics (Fizzics) has nothing to do with science. It is the name given to those with too much time on their hands and so spend all day watching bubbles rise in bottles of pop.
Of course, due to the nature of this rather strange pastime, it is by it’s very nature singular.
Last edited by After all it is free  on Tue 5-10-10 8:15; edited 1 time in total
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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rayscoops, from Google:
define:physic yields: purgative: a purging medicine; stimulates evacuation of the bowels
define:physics yields: the science of matter and energy and their interactions; "his favorite subject was physics"
Those are the first definitions from Google, but the others are broadly similar.
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rayscoops, definitely singular, hence I've changed the title which was driving me crazy
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FAQ
