After 50+ years of traditional photography, I went 6 months ago for drone video&photography. Incredible what the change in perspective can do... Anyway, the question is now related with a dominant tint I'm getting when I shoot at very high altitudes. I just shot 5.5 hours of videoclips & photos in the high lands of Argentina and Bolivia, between 3,800 and 5,500 meters above sea level. When I watched them, back home, on a serious 4K computer screen, I realized that they were terribly tinted in brown/magenta and now I'm struggling in post-production to color-correct them. I used the Auto White Balance setting for all the takes, and it seems that the higher I went the more brown/magenta the videos are hued. Any idea to avoid the same problem in future? (Yes, the good old "adjust the white balance every time you shoot pointing at a white piece of paper" would also do...). Thanks, folks.

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    When asking a question like this, you should usually include a description of the equipment you are using and how the files are being processed. Are you looking at NEFs? DNGs? JPEGs? What software, etc? – Clickety Ricket Feb 11 '18 at 15:09
  • I'm talking of video shooting, .mp4 format, 2.7 K resolution, PAL, 25 fps. Using a Mavic Pro drone with slight +1 Contrast correction and D-Cinematic color setting. – BigBoozer Feb 11 '18 at 21:16
  • @BigBoozer if this is primarily about video, you may want to have this Q&A migrated to the video.SE. – inkista Feb 12 '18 at 2:04
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    I don't think this should be closed as off-topic for reasons of being about video. Unless there are physical/electrical/optical differences between video equipment vs. photo gear that would produce the color temp effects in question, per the Vote-to-close text, "This question is about video in a context that is not likely to be relevant to still photography", doesn't seem to apply here. Photographers shooting at high altitudes presumably should have similar concerns as OP does. – scottbb Feb 18 '18 at 2:51
  • Having said that, @inkista's advice to possibly migrate this to Video Production isn't a bad suggestion at all. If this question becomes closed, or gets a poor reception here, it might get more love over at Video. – scottbb Feb 18 '18 at 2:53

Yes, color temperature changes with altitude. It gets higher (bluer) with altitude, but it should not get a magenta tint. If anything, the white spectrum is purer at higher altitude, so it should be more neutral on the green-magenta axis.

The effect is pretty minor though, and should be negated by auto-WB on digital cameras. I would expect the problem you are seeing to be caused by something else.

For slide film, many people use an 81B warming filter at high altitudes, though I've always considered that too strong and used either an 81A or no filter at all.

  • Thanks Aram, I also used 81A and 81B ...last century (!) when I was shooting films. But now with auto-WB I never had problems. This time it was a disaster. You can still find the dominant after heavy color correction, in my videos here: youtube.com/… – BigBoozer Feb 10 '18 at 21:10
  • There's a definite color cast in those videos, but I am not sure what is causing it. – Aram Hăvărneanu Feb 10 '18 at 21:13
  • Is the color cast present at lower altitudes? Which drone/camera were you using? – BobT Feb 10 '18 at 23:27
  • There is no color cast in all my videos taken at lower altitude, and - strangely - there is almost none in a subsequent video - that I am editing right now - shot at Lake Titicaca, at 3800 meters. Here the largest percentage of image is composed by green vegetation and blue water. I mention this to say that, with images largely composed by desert sand, rocks, reddish mountains etc. all took a brown-purple tint, while when the subject is more evenly colored the tint disappears. – BigBoozer Feb 11 '18 at 21:08

Usually if an image has a strong magenta tint, it is because some kind of warming filter is being applied.

At higher altitudes you get higher-energy blues because there is less diffused light from the ground. So, to a camera sensor this seems like a more intense blue environment. Some cameras and/or software will react to a lot of intense blues in an image by trying to warm it by shifting the colors into the magenta/red part of the color space. This causes areas that should be gray, black or shadowed to turn purple.

  • Thanks, that was my opinion too, after some thoughts. I am using a Mavic Pro, shooting in mp4 at 2.7 K /25 fps, with a very very slight correction of +1 Contrast. – BigBoozer Feb 11 '18 at 21:13

As one moves higher in altitude the atmosphere is thinner and the filtering effect of the atmosphere on the sun's light is reduced. It's the opposite of what happens in "golden hour" at lower altitudes when the sun is low on the horizon and must pass through much more air due to the angle. This means that as one moves higher in altitude, the natural light from the sun will appear bluer.

I used the Auto White Balance setting for all the takes...

How each specific camera model might react to the the change in altitude and the resulting bluer light will vary. It all depends on the AWB routines programmed into the camera. Even with the same camera it will often vary greatly depending on the contents of the scene and what colors those things are. It seems your specific camera reacted to the higher color temperature of the sunlight at high altitude by overcompensating in the opposite direction.

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