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I'm taking a photo of the setting sun, and want to capture the color of the sun accurately and objectively.

If we're talking about reflected right, I understand that the camera can't distinguish between yellow light bouncing off a white wall, and white light bouncing off a yellow wall. Therefore, white balance is a subjective game.

But when we're talking about incident light, it should be possible to objectively and accurately measure the color temperature of the sun — the average frequency of its spectrum. Is that reasoning correct? If so, how do I accurately capture the color of the setting sun itself?

The goal is that the color of the sun in the photo should be exactly the same as it was in real life, assuming I'm viewing it on a calibrated monitor. I often find that the brilliant orangish color of the sun is replaced by a more neutral yellow (cooler temperature), destroying the effect I'm trying to capture. The goal is NOT to cancel out the color of the sunlight, say by using a gray card.

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    Why would you want to do that? And if you do want to, just set the camera to auto white balance: It will take all that dramatic color right out! – feetwet Jul 27 '15 at 15:10
  • Just some thought for you ;) - what is the difference between yellow light and white light reflected of a yellow wall? - You end up with the same problem, you need to calibrate. The white balance is required to balance the individual colour channels in connection with the "tint" (as Capture One calls it). – DetlevCM Jul 27 '15 at 18:18
  • See imgur.com/gallery/5N3FA - take a picture of something white/grey - as in "you know to actually be that colour" and tell the camera "this is white" – Alec Teal Jul 27 '15 at 19:13
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    If you want the objective colour, just turn off white balance (and all the other automatic compensation mechanism). It's going to be nowhere close to your perception of the sunset, though. That's why white-balance exists, after all - humans do the white balancing naturally, while your CCD sees exactly what is there. – Luaan Jul 28 '15 at 8:29
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    You will also be up against dynamic range. A sunset here recently had the most amazing deep blood-red sun I have ever seen. However, on all the photos I took, although I could get the clouds the correct colour, the sun itself was blown out white in every shot. Out of interest I stopped down until the sun's disk had the correct colour, and the rest of the scene was basically black. So you may need a couple of exposures to duplicate what you are seeing, even after you get the colour satisfactory. – Whelkaholism Jul 28 '15 at 10:15
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But there is nothing objective about perception. If the goal is to attempt to reproduce the perception, the closest will be to set the white balance from a grey card which is not directly lit with the Sun.

  • But by what, then, should the card by lit? – feetwet Jul 27 '15 at 15:08
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    @feetwet - the card should be lit by the ambient diffused light, because the colour of the Sun as we see it is perceived relatively to the adaptation to that ambient light. – Iliah Borg Jul 27 '15 at 15:17
  • I'm taking this photo from my balcony, pointing the camera at the sun. Should I hold the grey card in front of the sun? Or should I turn around (with my back to the sun) and hold the card there, facing the sun? Or some other angle, like tilted up? – Vaddadi Kartick Nov 1 '15 at 3:58
  • Actually I think this is a poor answer, because a grey card is generally used to compensate a color cast, and not to preserve it; the question was about the opposite. Probably a spectral photometer pointed at the sun would give a correct CCT (Correlated Color Temperature). My guess is 4000°K or less. That means compared to the 5900°K near mid-day, the color temperature is "warmer" by about 2000°K. – U. Windl Aug 21 at 0:29
  • @ U. Windl - human perception involves chromatic adaptation, and that chromatic adaptation happens to eliminate casts, to a large extent. – Iliah Borg Aug 21 at 16:04
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As you say, white balance is a subjective game. The only way to do this in anyway objectively would be to process your photos in conditions where all the factors affecting subjectivity, i.e. the colour temperature of the ambient light, is the same as when the photo was shot.

In my Canon 5D Mk III, for example, this could be done as follows:

  • Shoot the sunset in RAW
  • Choose RAW Image Processing menu item
  • Adjust colour temperature in increments of 100K until what you see on the screen reflects what you see in the actual scene.

But then no doubt when you go home and view your photo on your laptop screen in a room light by your energy saving lightbulbs (you environmentally conscious person, you), your brain will tell you that your photos are more orange than they did when viewing them on your camera screen in the field.

This is the point of using white balance. White balance is to make photos "perceptually correct" not "objectively correct". An "objective" approach would dispense with white balance manipulations altogether.

The unfortunate thing about sunsets is that the sun (and even anything lit by the the combination of direct sunlight and skylight) actually appears orange to the eye, so to "correct" for it doesn't make any sense.

I know, it sucks.

  • I'm aware of the effect of different viewing conditions, but for this question, you can assume I'm viewing the photo on a monitor calibrated for its viewing environment. In your last paragraph, did you mean to say that the sun appears more orange eye than it really is (if you had an instrument that measures the color temperature of the incident light)? If so, I'd agree that perceptually correct != objectively correct, in this case. – Vaddadi Kartick Jul 28 '15 at 1:17
  • Are camera LCDs and EVFs calibrated well enough that this helps? I know that calibration depends on the viewing conditions, but some screens (like on smartphones) are calibrated so poorly that they almost never are accurate, exhibiting a blue tinge under most viewing conditions, for example. Are camera LCDs and EVFs equally poorly calibrated, or are they good enough for this kind of color comparison? – Vaddadi Kartick Jul 28 '15 at 1:26
  • Camera LCDs lie like politicians! – Michael C Jul 28 '15 at 1:39
  • @KartickVaddadi Color temperature is also a lie. The Sun is very much white to human eyes (which should be obvious - that's what they evolved for). Add sky scattering, and you end up with yellow - the blue light has been mostly filtered out of the direct sunlight. There's no "color temperature" to account for that - the direct sunlight is no longer even close to the perfect blackbody radiator where the concept of color temperature makes sense. As the sun gets lower on the sky, its light must go through more air, losing more blues and greens, eventually resulting in the orange-reddish colour. – Luaan Jul 28 '15 at 11:50
  • Doesn't it simply mean "Set the camera manually to daylight white balance and shoot"? So the sun will come out warm (yellow/orange/red). – U. Windl Aug 21 at 0:34
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When it comes to the sun, objectivity is harder than that. Color of the setting sun is changing while it's descending - and white balance basically means that you choose the light of the sun as white point. It differs minute-to-minute in last stages of sunset, but overall - you should decrease color temperature if you want to set white balance correctly during sunset.

tl;dr Start at 5,780 K before sunset and decrease it to your liking

And remember - after sunset the sky is starting to get blue due to Tyndall effect - so after an hour after sunset your white balance should go up.

  • Right, I'm not worried about it changing in the few seconds between setting the white balance and taking the photo. – Vaddadi Kartick Jul 28 '15 at 1:12
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I'm a little unclear what you're asking, but if you literally want to measure the color temperature of the light from the setting sun, you can take a photograph of the setting sun in raw mode, making sure not to overexpose the disk of the sun. Then, in your processing software, you can set the white balance by clicking the eyedropper on the disk of the sun. You can then read off the custom color temperature and tint that resulted. (Once you set the white balance this way, the disk of the sun will of course be gray or white.) This approach assumes that your camera has a good, accurate profile in Lightroom or whatever software you're using.

If you're asking whether there are instruments that can measure the color temperature of incident light, there are indeed. For example, the Sekonic Prodigi Color C-500 Color Meter, which works a lot like an incident light meter, but for color temperature.

  • Please see the updated question. I don't want to cancel out the color of the sun. – Vaddadi Kartick Jul 28 '15 at 1:12
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Interesting to consider what "color temp" or "WB" causes the monitor to show the actual same color.

The same spectra would indeed be the same in a real sense. But we don't have that.

The same tristimulus RGB values should "look" the same, at least to a primitive stage in processing in the eye. But the brain interprets that based on the brain's own WB setting, so it still won't look the same even though it's truly identical in the physical meaning!

That's the whole deal with WB. If you remember when other people developed and printed film for you, and they came out orange if shot indoors, that's the thing. The print is "right" but looking at a print doesn't change the mind's current WB to what it was when you were seeing it live. In fact, the pigments on the page are interpreted using the mind's current WB, so they ideally would cancel out and the print should be made to a standard white point.

You can't capture the complete perception of the sunset. An accurate color space mapping will not evoke as much of the same feeling as a more poetic interpretation would. That's why people still take pictures of the sunset, and why it's "art". You could get a spectrometer and deliver a chart of scientific readings, but that's not what we're after here.

"I'm not worried about it changing in the few seconds between setting the white balance and taking the photo" No, don't "set" the white balance in the camera. You don't care, as the RAW data will be processed later with a more powerful computer and under your guidance. Shoot a test target immediately before, and use that to help you figure things out when you "develop" it. That takes no time or fiddling; it's just another photo.

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