# Does Earth's latitude affect the color of light?

I was talking with a friend about what conditions can affect color, gamma and white balance, and how to get in order these variables into the configuration to set up and get a good shot.

Beside the angle of the sun at some day (we will assume that the time is every the same in every place), and related to the season (but also we will assume that the same season in every place).

Also with the assumption for the same conditions and camera setup in every place...

So, first question:

1) Is there a change in the color or white balance or gamma or something taking one shot for example at tropic, at equator and pole, because the light from sun changes in every latitude?

For example, you get less/more color in equator than in north tropic, and both are different than on the south tropic?

If this is true:

2) Is the difference substantial, for e.g., from Lat 40S to 50N? (This assumption must be without seasons of course. I'm not talking about distances to the sun, so... for e.g. Summer in 40S and summer in 50N, the same day (21-12 for South, 21-6 for North)

3) Can it be corrected?

4) Do I have to take any consideration to set up my camera if I travel from one place to another place?

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Assuming things that change to be constant in order to ask a theoretical question about how things would be different is kind of pointless. Plus, you also forgot altitude which trumps most of the latitude considerations for a large portion of the globe. – Itai May 20 '13 at 14:20
the season are not caused by distance to the sun, they are caused by angle of incidence. – Paul Cezanne May 20 '13 at 14:43
Itai: I never thought in altitude, but I remember my friend told me about taking pictures in Machu Pichu where altitude conditions are applicable as well. Yes Paul, I make this question thinking in that, that's my concern about latitude – Leandro Tupone May 20 '13 at 14:56
Sorry if this question is a little stupid, I'm learning and as you can see, even a concern at this point of my knowledge-curve is a warning :D – Leandro Tupone May 20 '13 at 14:58
@Leandro - Some of your questions may be basic, but they still ask interesting things and I'd hardly call them stupid. Uninformed perhaps, but we all started somewhere. This question also has a lot of subtleties if interpreted as the broader question "what environmental characteristics impact the quality of light outside and how do you deal with those differences?" – AJ Henderson May 20 '13 at 15:22

Latitude doesn't directly change the sun's light in any way. The angle of the sunlight and the amount of atmosphere it has to pass through both indirectly impact the intensity and color of the light, but this shouldn't have a significant impact on taking photos as long as you properly meter and white balance.

The bigger direct concern would be the angle of the light which you simply manually take in to account based on where in the sky the sun is. While the angle impacts the amount of atmosphere and thus the color and intensity, the direction of the light is a bigger concern. Light coming from above lights a scene differently from light coming in from the horizon and the angle the light is coming from impacts how you shoot.

The reason it can seem different is because of the effect of the atmosphere and surrounding terrain on the quality of the light. This is going to be impacted in a small part by latitude but is going to be much more dependent on season and weather conditions.

The way to correct for changes based on the day and weather is to use a grey card (or really any piece of white or medium grey paper can work) to manually set the white balance for the image. A full professional grey card can also be used in post to adjust for contrast/brightness/white balance/etc.

The shooting habits and techniques shouldn't change from one location to another. Even going from indoors to outdoors has fairly little change in how you assure good color, you just have situational techniques that you use based on criteria (such as if the shadows are too strong, use a fill light, or if the colors of the light don't match, use a filter to match them if possible).

Some situations are more likely to need a certain technique than others, but for the most part, light is light and you deal with it the same regardless of source. Which is to say, you deal with it based on conditions.

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perfect, but related and maybe, there is something like the grey card at 18% reflective but in color for DSLR? – Leandro Tupone May 20 '13 at 14:48
DataColor does make a color swatch card that can be used for really fine tuning of color, but a medium grey is going to give a good read of the levels of red, green and blue seen as "white" and should produce colors that are accurate enough for most professional uses. A little more could be gained from doing a card that includes black and white points as well, but the gains become pretty small, particularly when a fair bit of color grading tends to be to feel as opposed to being lab accurate. – AJ Henderson May 20 '13 at 14:50
Personally, I carry a Whibal card in my kit. It is a sturdy chunk of solid plastic that is the same gray color pigment throughout. It is approximately 18% gray, but more importantly, its spectral response is very close to dead flat through the visible region meaning that it is a reliable gray reference under any (visible) light and with any sensor. Being a block of plastic, it doesn't pick up coffee stains easily. It also has bright white and black patches and a high-contrast sturburst pattern. – RBerteig May 20 '13 at 22:57
How does latitude affect only the sun's intensity? If you are talking about the angle of the sun in the sky, that also affects the temperature of the light. The more atmosphere the rays have to travel through, the warmer the color of the sun's light becomes. – Michael Clark May 20 '13 at 23:36
@MichaelClark - yes, agreed. I think you said it better in your answer, but my point was that it has nothing to do with the latitude other than the impact that the latitude has on the amount of atmosphere and the temperature has on the local fauna. It isn't a direct side effect of the latitude. I guess it also doesn't impact intensity much either though since it varies throughout the day and season. – AJ Henderson May 21 '13 at 3:25

The color of sunlight reaching the surface changes based on the thickness and quality (in terms of things like particulate matter and water vapor suspended in it) of the air it passes through. Whether the sun is at an angle 30º above the horizon because it is noon in winter at a high latitude or because it is 4 p.m. in the tropics doesn't make much difference if both locations are at the same altitude. When the sun is at a low angle in the sky, such as when setting or rising, the rays must travel through much more atmosphere than when at higher angles in the sky. The condition of the air those rays are passing through can have a dramatic effect on the quality of light that reaches the surface.

The seasons affect the light for a particular location because the amount of moisture and particulates in the air will vary from season to season in many locations. If a place is outside the tropics then the maximum angle of the sun in the sky is lower in the winter than in the summer. This difference increases dramatically as you approach the arctic circles.

In places that have snow covering the ground in the cooler months, the light reflected from the snow will look much different than the same light reflected off of lush green meadows which will look different than the same light reflected off of urban concrete, a sandy beach, or a dusty desert - even when the sun is at the same angle in the sky.

Which of the above factors is most influential varies with the situation as well. In the middle of the Sahara desert, the atmospheric conditions do not vary that much, so the angle of the sun is normally the largest variable - at least until a dust storm develops. In the Pacific Northwest of the United States, cloud cover is highly variable and can potentially be a greater influence than the angle of the sun. There's not much difference between overcast at noon and overcast two hours before sunset. Above the timber line on an exposed Rocky Mountain peak the light will be much different than descending just a few hundred feet into a lush forest of green.

You can always correct for the differences in the temperature and amount of light using colorimetric tools and varying the exposure value. But why would you want to make every place you go look exactly the same?

Does Earth's latitude affect the color of light?

Only indirectly, as the latitude determines the sun's angle in the sky for a given time on a given day, and also influences weather related environmental factors such as atmospheric contents and ground cover.

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That's a good question! Also I learn a lot about optics and atmospheric circunstances with your answer! thx a lot! :) – Leandro Tupone May 20 '13 at 18:28

1) There is a change on the color or white balance or gamma or something taking one shot for example at tropic, at equator and pole, BECAUSE the light from sun changes in every latitude?

Yes, absolutely, but the difference is not more substantial than the difference between seasons or time of day.

2) Is the difference substantial, for e.g., from Lat 40S to 50N? (This assumption must be without seasons of course. I'm not talking about distances to the sun, so... for e.g. Summer in 40S and summer in 50N, the same day (21-12 for South, 21-6 for North)

Not more substantial than the difference between seasons or time of day.

3) Can be corrected?

Yes, you can use a gray card

4) I've to take any consideration to set up my camera if I travel from one place to another place?

Do you change your camera settings between morning and evening? do you change your camera settings between summer and winter?

And, most important, do you want to completely compensate for the light? sunset is orange, when I take a sunset picture I want to show this and not compensate for the light color balance - if you always set your camera "correctly" you will have pictures that all look alike.

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Shouldn't the intensity change but not the color? There might be subtle changes from differences in reflected light, but the color of the sun doesn't change based on where on the planet you are. – AJ Henderson May 20 '13 at 14:20
@AJHenderson - you are right, the color of the sun doesn't change, but the color of light reaching the ground is also effected by the weather and the surrounding landscape and those are very different in the tropics and the poles – Nir May 20 '13 at 14:29
yeah, but that's weather and landscape, not latitude – AJ Henderson May 20 '13 at 14:31
Yes, I was thinking on color depth, thinking from the point of view that the light enters on different angle in the atmosphere, like if you change the environment (a picture in the water for e.g.) – Leandro Tupone May 20 '13 at 14:34
@Leandro - well talking about shooting in water, it actually changes considerably based on environment due to temperature and composition. There are actually cameras designed for shooting underwater that have different modes based on depth, temperature and if it is blue water or green water. Total depth of the water also matters as reflections off the bottom impact things a lot. – AJ Henderson May 20 '13 at 14:47

Okay, it is a little primitive, but it's the easiest way I know to illustrate why the Sun's light gets warmer as its angle in the sky is reduced. When straight overhead, the light rays from the Sun travel through much less atmosphere than when the Sun is on the horizon.

This is the primary reason that both the Sun's intensity and color are affected by the angle of the Sun in the sky. Atmospheric conditions in the portion the rays travel through to reach a point on the ground are also a huge variable in how the Sun will appear to a surface observer. The density of particulates (mainly dust), water vapor, and condensed water (clouds) will absorb and reflect a portion of the Sun's rays that pass through them.

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excellent!!!!!! – Leandro Tupone May 21 '13 at 13:54

The most significant difference is the dynamic range required to capture the sun areas and the shadow areas. The colour temperature you always have to manage, no matter what, but the dynamic range can be hard to manage, because the light in e.g. California vs Denmark can be the difference between being too hard without shooting HDR in California, vs being fine with shooting raws in Denmark. I've also had some discussion with jrista about some cloud images I took at noon in a winter day in Denmark, and they looked like clouds near sunset at other locations.

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good example! I live in Argentina that is not too big but is very large country, from antartic to tropical and higher. This information for me is very useful. – Leandro Tupone May 20 '13 at 16:37