Astronomy

Why does the Sun show different colour at midday and at morning?

Why does the Sun show different colour at midday and at morning?


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As we see every day in the morning the sun shows a red-orange colour but at midday has a blue-white like colour why?

Is it concerned with the distance from the earth or about intensity? How do you see it?


Sunsets are red because the sky is blue.

Air, while it appears colorless actually scatters light just a bit. This is not the same as absorbing the light, but more like how light is scattered by fog. If you are driving through fog with your headlights on, part of the light from their beams bounces off the fog particles and lights up the fog well outside the beam and some of it even bounces multiple times coming back to your eyes.

Air is much clearer than fog, but it does scatter light just a bit. What's more, it scatters blue light more than green, and green more than yellow, and yellow more than red. So while the Sun's light in space is quite white, as it passes through the atmosphere on a sunny noonday a lot of the blue light gets scattered, while very little of the red does. That blue light bounces many times and is the source of the blue sky light. The loss of that blue light makes the sun appear redder.

At noon, the light comes down from high overhead and passes through a minimal amount of atmosphere and only some of the blue light is scattered. At sunset (and sunrise) the light comes in at a long, low slant and passes through much more of the atmosphere, and nearly all of the blue and even most of the green is scattered (and much light is absorbed, too), leaving mostly red and orange light left.

Hence the reddened sun.

See Why Is the Sky Blue? and Why Is the Sunset Red? for a bit more including some diagrams.


Neither. As @User123 commented, it depends on the angle between where you are and the Sun. If the Sun is low in the sky, sunlight has to travel through much more of the atmosphere than at midday when the Sun is higher in the sky. The intensity of the Sun is basically constant, and the distance from the Sun does not vary between morning and midday.


Why does the color of the sky get lighter, the closer it is to the horizon?

It is because of so called "Mie scattering" of sun light in the haze, contained in lowest layers of athmosphere. The light passing through the haze changes its direction to random other directions. So, it catches light from sun and directs some of it towards your eyes.

When you look up, the layer of the haze is pretty thin and does not significally affect color of the sky. But when you look to horizon your look goes through about 5 km full of the haze, and your eye catches all that scattered light.

While I cannot contribute much more information. I feel it is worth noting that rayleigh scattering alone provides a brighter horizon with the sun overhead (e.g. midday hours). Mie scattering also contributes to a brighter horizon (e.g. a hazy day) and the white halo around the sun.

Another effect that contributes to the lighter horizon is ground albedo. Light reflected from the ground bounces back into the atmosphere and gets scattered all over again. This results in a not-insignificant lighting of the sky near the ground (intuitive, if you imagined the ground being lit like under midday sun but no sun in the sky). Here is a comparison of simulated skydomes with various ground albedos. From this paper here

Isn't it the opposite? When you look towards the horizon all of the blue light has been scattered in other directions. You're seeing less scattered light.

When you look up you only see scattered light, and blue light gets scattered the most so it looks blue.

But when you look to horizon your look goes through about 5 km full of the haze

Most of the haze and dust in the atmosphere is troposphere. The top of the troposphere/ bottom of the stratosphere is at about 33k feet / 10km. So when you look straight up, you're looking through

10km of haze. When you look at the horizon, you're looking slantwise through that 10km, far enough that the curvature of the earth comes into equation. Bottomline though, it's in the 100's of km, not 5 km.

I'm a bit confused—how does the thickness of the "haze" change when you look up or toward the horizon? Considering that the atmosphere would be a spherical shell around the Earth, there shouldn't be that much of a distance difference between looking straight up on an axis that goes through the earth and looking along a tangent touching the earth right?

Actually, it's a bit of statistics, mixed with physics. The scattering effects described by others aren't wrong, they just aren't describing the whole picture of the question i believe you are asking. Two things in particular will contribute to the sky appearing lighter during sunset the first being the contrast ratio between the sky and the ground being higher since the light rays are being projected onto a near-parallel surface causing the luminosity of the ground to drop and the second being that a larger proprtion of the sun's light is now being absorbed into the atmosphere via scattering affects. When the sun is directly overhead, each square mile of atmosphere only has a distance as thick as the atmosphere's height for it to absorb and scatter the sun's light, meaning that the distance is relatively small to the distance it will travel through the atmosphere at sunset. During sunset, the sun's light is coming through the atmosphere at a low angle, which causes the light to effectively travel through even more miles of atmosphere than when shining straight down, allowing the atmosphere to absorb and scatter an even larger portion of the sun's light, making the sky appear brighter.


What You Can Do

  • Limit time in the midday sun. The sun's rays are strongest between 10 a.m. and 4 p.m. Limit exposure to the sun during these hours, even in winter and especially at higher altitudes.
  • Do not burn. Sunburns significantly increase the lifetime risk of developing skin cancer, especially for children.
  • Seek shade. Shade is a good source of protection. However, keep in mind that trees, umbrellas and canopies do not offer complete sun protection.
  • Use extra caution near water, snow and sand. These three materials reflect the damaging rays of the sun, which can increase your chance of sunburn.
  • Avoid sun tanning and tanning beds. UV light from tanning beds and the sun can cause skin cancer and wrinkling.
  • Wear protective clothing. Wide brimmed hats offer good sun protection for your eyes, ears, face and neck. Sunglasses that provide 99 to 100% UVA and UVB protection will greatly reduce eye damage from sun exposure. Tightly woven, loose fitting clothes will provide additional protection from the sun.
  • Always use sunscreen. Apply a broad-spectrum sunscreen with a SPF of 30 or higher on all exposed skin 20 minutes before going outside. Reapply every two hours, or after working, swimming, playing or exercising outdoors.
  • Watch the UV Index. The UV Index provides important sun safety information to help people plan outdoor activities.

​ Regardless of your exposure to UV rays, conduct a monthly self-check to look for any skin abnormalities. Have a friend or family member check your back and scalp. Look for bumps or sores that don't heal or for moles that have changed size, color or shape. It’s important to visit your physician or a dermatologist for regular skin checks and to have any new or changing mole evaluated. When caught early, most cases of skin cancer can be cured.


Earth is wrapped in its atmosphere

So we know why the sky is bright during the day and dark at night. And we know sunbeams come in different sizes, or “wavelengths”.

But how does it become the gorgeous colours we see during sunset and sunrise?

This happens because of an important blanket of air wrapped around Earth, called the atmosphere.

Earth’s atmosphere is made up of many very tiny objects called molecules. In fact, all things are made of molecules, including you and me.

But each molecule is much, much smaller than a grain of sand. They’re so small you can’t see them without a microscope — you can only see the bigger things they make.

If you were an astronaut onboard the International Space Station, you’d have crossed Earth’s atmosphere to get there. NASA


Why do your photos end up looking washed out and grey?

Colourful bird, rich light: The bird&rsquos a Galah, and the light was ten minutes before sunset.

Sunlight is harsh and desaturated in the middle of the day and only gets worse when it&rsquos overcast. Light like that will result in washed-out photos like the one of the Willie Wagtail shown below.

You might be thinking I&rsquom exaggerating. I mean, things might have looked great to your eyes when you took the photo. But to understand what&rsquos going on you have to pause for a moment to think about how clever your eyes and brain are.

The harsh, desaturated early-afternoon light washed most of the colour out of this photo of a Willie Wagtail.

Stand in a room lit only by an old incandescent bulb, and your eyesight immediately adjusts to the yellowish lighting, to the point where you don&rsquot even notice how yellow everything is. Your camera notices though, and if its white-balance isn&rsquot working properly it will record everything with a yellow tinge. This same tendency for the eyes/brain to &lsquoadjust&rsquo means we also often don&rsquot notice just how desaturated the colours can be on a bright, sunny day either. But while cameras might have that auto-white-balance trick, there&rsquos not a lot they can do about those desaturated midday colours without making things look fake. So they just record things as they are.

So the first thing you want to keep in mind is the time of day you take your shots.

Why is the middle of the day so bad?

At midday, the sun&rsquos at its highest point in the sky and therefore its light travels through the shortest possible path through the atmosphere to reach you. The diagram above shows what I mean.

Now compare that with the first hour of sunlight in the morning or the last in the evening, which I&rsquove drawn in the next picture, above. At those times the light has to travel through a lot more atmosphere before it reaches you. That atmosphere has lots of tiny particles in it, and they infuse the light with the kind of warm, golden tones missing from your midday shots.

The two birds here (Silver Gull and Darter) were photographed in the same place with the same camera and even the same lens. The only difference was that the Gull was photographed at midday (you can see from the shadows that the sun was directly above it) and the Darter in the rich, golden light half an hour before sunset.

The Golden Hour

Photographers sometimes refer to the last hour of sunlight in the evening, or the first hour of sunlight in the morning, as the Golden Hour. The word &lsquohour&rsquo in Golden Hour shouldn&rsquot be taken too literally though because the really great light might only last for a few special minutes.

Standing outside when the light&rsquos at its most saturated in colour, a whole bunch of wonderful things happens:

  • Colours start reaching beautiful levels of intensity, with reds and yellows appearing to glow from within, and the camera eats it all up, giving you the kind of fantastic colours in your shots that other people never seem to get!
  • When the sun is behind you instead of above you, the sky won&rsquot be bleached white by glare any more. Say hello to proper blue skies in your shots.
  • The light will be hitting your subject front-on or from the side, instead of from above. That&rsquos actually a really big deal, because it means those harsh midday shadows get filled in with rich colours (see the graphic below.)
  • Because the light isn&rsquot as bright during the Golden Hour, your camera no longer struggles with dynamic range problems. So where you might normally get blown-out patches of pure white, those areas fill up with colour.

At midday the light is harsh and comes straight down, hitting the top surfaces which we can&rsquot see properly. During the Golden Hour the light is saturated with colour and floods into the surfaces we can see.

Perfect storm

When you think about it, that combination of factors listed above is creating a kind of &lsquoperfect storm&rsquo of colour. And professional photographers know it. That&rsquos how the top landscape photographers get their eye-popping colours in their postcard shots. Their cameras are the same, or very similar, to what you have, but they&rsquore getting up crazy-early in the morning to be at their photo shoot locations before the sun comes up, so they can be set up and ready for the best colour as the sun rises. Or they will arrive at the photo shoot late in the day to get the best light before sunset. Whether they choose sunrise or sunset will often depend on whether their subject will look better lit from the east or the west. Or like in my case, in which case it&rsquos how much they like to sleep in.

I should point out here though that unfortunately there are no guarantees, for the simple reason that you&rsquore dealing with that exasperating, unpredictable phenomenon which we call weather! So, cloud cover or haze can ruin everything, but then if the weather does cooperate then you&rsquoll be in a position to capture the best kinds of colours.

Polarising filters

If you must work in the brightest hours of the day, you&rsquoll be grateful for a trick that cuts back on the glare and restores some welcome colour to the skies: using a polarising filter.

For a polarising filter to get the deep blue appearance in the sky, you should point the camera in a direction that&rsquos 90 degrees from the sun.

Midday light sucked the warm tones out of this building but at least my polarising filter put some good colour into the sky. Like the other examples on this page, this image did not require any digital manipulation to achieve that colour.

Polarising filters enhance the ability to see into water (by cutting down the glare on the water surface), darken skies (while keeping the clouds white) and reduce the amount of reflected glare bouncing off surfaces like foliage. The result of all that is more colour in your photos.

When you&rsquore using a polarising there are a few things you need to know:

  • With autofocus digital SLRs the type of polarising filter you&rsquoll need is a Circular Polarising filter.
  • You need to rotate the filter on your lens to find the most effective angle. So for example, if the end of your lens rotates as you zoom then you&rsquoll need to keep adjusting your polariser filter a lot more
  • If you want to darken the sky, the polarising filter is most effective when you are facing in a direction that&rsquos 90 degrees from the sun. So if you&rsquore facing the sun, or have the sun directly behind you, the effect won&rsquot be noticeable. I&rsquove rendered up a quick graphic above to show you what I mean.

Other ways of working in the middle of the day

The best way I know for putting rich, warm tones into your photos is to use a gold reflector. Gold reflectors are a sheet of gold-coloured foil. You hold it so the sunlight reflects off it and into bounces onto your subject. Professional photographers use big disks of foil held by an assistant while they take their outdoor shots, but you can also get little inexpensive ones for using in things like macro photography.

That&rsquos how I got the nice colours in the photo of the frog shown below. I used an old, cheap tripod to hold the reflector in place and then used my proper tripod to take the shot. The colours ended up just as good as the best golden-hour light but I got them in the middle of the day.

An Eastern Dwarf Tree Frog photographed in the middle of the day came out in great colour thanks to the use of a gold reflector. I used a bit of wire to attach the reflector to an old cheap tripod.

And there are other ways to get great shots possible at all hours of the day (and night). It&rsquos just that you have to be a bit resourceful around the middle of day if you want to get good colour into your shots. For example, you can get your subject to stand next to golden-coloured walls. And of course there are always the polarising filters (mentioned above) to cut back on glare and get some nice blue into the skies.

A nearby bushfire caused the sunlight to take on a rich, orange colour, which allowed me to get good colour into this picture of a Crimson Rosella.

Taken in the middle of the day, this macro photo received all the saturated light it needed from the flash

And sometimes the unexpected works in your favour. When I saw the Crimson Rosella in the nearby photo there was a hazard-reduction bush fire burning a few kilometers away. The sky was therefore full of smoke, which softened the light and gave it a rich, yellow-orange tone similar to the Golden Hour. All I had to do was wait for the bird to jump out of the shadows and into a spot illuminated by that light and the colours speak for themselves.

And then there&rsquos macro photography, where it&rsquos likely your flash will overwhelm the surrounding light anyway. The photo of the bee shown here was taken only a few minutes before the Willie Wagtail shot at the top of this page, yet it doesn&rsquot lack the warm tones.

As for photography other than macro, professional photographers use all sorts of tricks to restore the warm tones in the middle of the day. For example they might use large sheets of shiny gold foil to reflect warm light onto their subjects. Or they will put yellow gels over their flash for the same reason. If you look around and be a bit resourceful there is nothing stopping you from getting better colour into your shots in most situations.

How I work if the light is really harsh

We can&rsquot always pick the times or places we work, so if you&rsquore out in the middle of the day, you might be interested in my technique for working in harsh light.


Does the color of the sun really matter?

Some of you may wonder if the color of the sun really makes a difference.

Well, the color of the Sun is actually significant for astrophysicists. A technique called spectroscopy is used to split the spectrum of light coming from a given star. This is done because splitting can give clues about the characteristics of the star from which the light is emitted. It can help astronomers estimate if a star is made of heavier elements or lighter elements, determining its age and behavior patterns.

Color also helps scientists estimate the temperature of a star. Contrary to intuition, cooler stars are actually colored red. Beteigeuze, a relatively cool star with about 3500 Degrees Kelvin, has a decidedly reddish color.

Hotter stars, such as Rigel, which lie above 10,000 Degree Kelvin, appear bluish. Our sun is estimated at 5800 Degree Kelvin, and when viewed from outside the Earth&rsquos atmosphere, it appears white.

For eons, we lived with the idea that the color of the sun is yellow. In fact, we are so accustomed to the idea of a yellowish sun that astronomers often artificially alter the images of our white sun to make it appear more &ldquonatural&rdquo!

Now that you know all this, next time a teacher asks you to draw a picture of the Sun, draw it in white instead.

If you&rsquore asked why your sun is not yellow, give a quick lesson about the atmosphere, the light, and the world around it!


Why does the Sun show different colour at midday and at morning? - Astronomy

During sunrise and sunset, a good opportunity arises to observe different aspects of clouds. During these periods, changes in the contrast and colour are observed as well as structure of the clouds. Such sunrises and sunsets can develop into some of the most spectacular events that exist in meteorology.

Obviously, sunrise and sunset are mostly noted for the associated changes in the colour of the sky especially around the sun. On some occasions, clouds will also reveal different colour patterns if present around sunrise and sunset. It is very difficult to describe the various colour changes that occur with the different clouds around these times. But there are general stages that are associated with the times from dawn to sunrise and sunset to dusk.

The heights of the clouds have an important influence on the length of times that cloud reflections occur. The higher the cloud, the longer the cloud bases will be able to reflect light. In fact, high clouds will reflect light for periods of up to 30 minutes whilst low clouds will typically reflect light from their bases for around 5 to 10 minutes. The reason for such a vast difference is that lower level clouds near the horizon are much closer to the observer ( around 1 to 15 kilometres away) than clouds at higher levels which may be up to a few hundred kilometres away. The cloud bases of higher clouds therefore reflect light well before sunrise and remain so until just before sunrise. The same situation still applies for sunset but in the opposite order.

The process of sunrise and sunset obviously occurs in a set pattern. Let us consider only one level of cloud in the sky. The cloud closest to the horizon will reflect light first. Gradually, clouds further away will also begin reflecting light. The process continues with colours changing from red and pink to yellow although occasionally some blue or violets are also observed. This of course depends on the heights of the cloud and the patterns of their bases.

Now, if combinations of clouds occur, then different patterns will be observed representing the different reflections of light from different levels of clouds in the atmosphere. This means that the higher clouds are still reflecting light from the sunrise for instance and lower level clouds are only observed as darker regions with no light being reflected from their bases. In the case of the lower clouds in particular, their shadows are observed as well as the sun's rays. This provides the observer with the opportunity to observe the outline structure of the clouds, especially cumuliform clouds with rounded tops such as cumulus.

During sunrise and sunset, even the same types of cloud may appear different in various regions of the sky. Cumulus, for example, will reflect more light at the opposite regions of the sky to that of the sun as compared to cloud closest to the sun. This creates a varied contrast and must be taken into account by observers trying to determine the different types of clouds in the sky.


Why does the red color appear at the horizon during sunset?

The red colour in the sky at sunset (and sunrise) is due to an effect called Rayleigh scattering. There is a similar form of scattering called Mie scattering which is responsible for the white colour of clouds.

Particles in our atmosphere that are approximately the same size as the wavelength of visible light cause the white light from the sun to scatter and split into individual components. Oxygen and Nitrogen (the main components of our atmosphere) scatter violet and blue light due to their small size. This is why the sky appears to be blue in the day time, especially at midday when the Sun is closest to us.

During sunrise and sunset the distance that the light has to travel from the Sun to an observer is at its greatest. This means the a large amount of blue and violet light has been scattered so the light that is recieved by an observer is mostly of a longer wavelength and therefore appears to be red.

For more information try looking at http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/mch/sct.rxml
Answered by: Edward Rayne, Physics Undergraduate Student, Cambridge UK

'If I have seen a little further it is by standing on the shoulders of Giants.'


A Beginner’s Guide to Colour Temperature

Lord Kelvin, AKA William Thomson has a lot to answer for. It was this Glasgow University based physicist that developed the scale of measuring temperature that we use in photography today. So why does a scale of temperature have relevance in photography? Well the Kelvin scale also measures the colour of light. The science of this is somewhat complicated but put in it’s simplest terms, if you have a pure black radiating object and heat it up until it is glowing, when the temperature is below 4000K it will appear reddish, above 7500K it will seem bluish.

So why is this important to us photographers?

Well, light at different times of the day and under different conditions will have different colours. Our eyes are so highly developed that we do not see this change, our brain quickly adapts to the difference but colour film and more recently digital sensors cannot adapt.

In terms of film, it can only be set to one color temperature, usually 5500K which is the average colour of the shade on a sunny day at noon, or, 3200K which is the temperature of tungsten light, for example the average household light bulb or professional photoflood studio lights. Digital sensors can be set to a range of colour temperatures but rely on one of two things to get the right white balance – the camera’s metering system or the user setting it manually.

Neither of these are entirely infallible so if we can understand a little of what the colour of the light is in a given scene, we can improve the colour rendition of our images.

Let's start off with daylight – as mentioned the temperature of the shade on a sunny day around midday is around 5500K, however if clouds start to obscure the sun, the colour temperature will go up to 6000K-7000K – this is quite a bit bluer. Generally your camera’s colour meter will be able to deal with this, but where it has problems will be at the beginning and end of the day or when there are large blocks of a single colour in the image.

During the sunrise and sunset times, the temperature of the light is much cooler, which ironically is warmer in look i.e. reddish yellow. Because the camera’s sensors are tuned towards shooting in the midday sun, they can, if used on auto white balance, try to over correct the colour moving it towards what it thinks should be noon daylight. The effect of this on your beautiful sunrise or sunset shot is to remove some of the rich reds or yellows by neutralizing them. To counter this effect we can use on of the camera’s preset white balances or set a manual white balance. The best setting for a sunset is actually the daylight preset, or around 5200K if setting manually. This will render the color as seen with the rich yellow/reds intact.

When shooting an image with a large block of single colour, for example a large green field, it’s best to use a preset for the actual conditions, for example the cloudy setting, or to take a manual reading. To do this you will need a plain white piece of card. Place it in the direction you will be shooting and measure the white balance from the card. You may need to refer to your camera’s manual on how to do this or see our guide on how to set your white balance manually.

When shooting indoors, you will find that flash light is somewhat bluer than daylight, although most camera’s will automatically detect when the flash is being used and compensate. Problems can arise when shooting under fluorescent light, for several reasons chief amongst them is that different fluorescent tubes can have different colours and that the colour of the light emitted by these tubes does not fall easily on the Kelvin scale.

Mixed lighting can also be problematic, for example when shooting in the Blue Hour, balancing the available light with neon signs and street lighting, here, experimentation will be the best policy.

Despite all this, there is one universal technique for solving most colour temperature problems – shooting RAW. As the name suggests, a RAW file contains only the direct data read from the sensor without any corrections made to it. Because of this we can manually set the white balance in post production using a RAW convertor, ensuring that we get the exact colour we require in an image without sacrificing the quality.

Hopefully this basic rundown lets you adjust for the hues of your own shots!

Jason Row is a British born travel photographer now living in Ukraine. You can follow him on Facebook or visit his site, The Odessa Files. He also maintains a blog chronicling his exploits as an Expat in the former Soviet Union


If the Sun is supposed to be producing white light, why does the sun appear yellow to the eye instead of white?

We need to start with the fact that white light is a combination of all colors produced equally by a glowing object. A glowing object that appears blue is blue because it's producing more blue light than it is producing red, orange, yellow, green light. The color of a glowing object depends on the temperature of the object. Now we can proceed to your question. Two Reasons why the Sun appears yellow: 1. The Sun's surface temperature (5,500 degrees C) produces a range of visible light (red to blue) in which yellow is the most plentiful, but not much more than other colors it produces. If the Sun were cooler, say 2,500 degrees C, it would look red, like the stars Antares and Betelgeuse. Or if the Sun were hotter, say 15,000 degrees C, it would look blue, like the star Rigel. 2 The Earth's atmosphere acts as a kind of light filter. Some colors are filtered more than others. The Sun is a yellow star, but the Earth's atmosphere makes the Sun look more yellow than it appears than if you were to observe it from space where it would appear more white than yellow. But you don't have to leave Earth to see that the Sun is really less yellow than it appears. If you are in the Rocky Mountains at 11,000 ft elevation, the Sun looks less yellow and more white than it does at sea level. There are fewer air molecules at this elevation to filter the Sun's other colors. Imagine what the Sun would look like from an airplane at 40,000 ft altitude--quite white! Also, when you are able to look at the Sun where you live, it's morning or late afternoon. It's easier to look at the Sun for a few seconds than it is a noon. The Sun appears more yellow at those times than it would if you were to observe it at noon (12 PM) when Sun is highest in the sky for the day it's at its brightest and whitest--hard to look at. Because of the Sun's high position at noon, the sunlight has less air to travel through. Less air means less filtering of other colors. Remember: Light appears white because all colors are equally reaching your eyes. So, at noon the Sun appears to be more white, less yellow--closer to the way it really is! (Don't try to make this observation without hi-tech eye protection).
Answered by: J Taras, M.S., Earth Science teacher, Slate Hill, NY

The short wavelengths (blue) of light from the sun are scattered by the atmosphere (which is why the sky appears to be blue.), leaving behind the longer (yellow-red) wavelengths.. From a high-flying airplane, or from the moon, the sun appears to be white.
Answered by: David Kessel, Ph.D., Professor, Wayne State University, Detroit

'Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.'