Quick Question

[hjscm]

OKay how come in photography when you adjust white balance lower numbers turns more blue and higher numbers turn yellow.  now for imstance my fish tank the lights are opposite.  lower temp is yellow and higher temp is more blue.

thanks
chris

[AndrewKulin]

OKay how come in photography when you adjust white balance lower numbers turns more blue and higher numbers turn yellow.  now for imstance my fish tank the lights are opposite.  lower temp is yellow and higher temp is more blue.

thanks
chris

In nature, the colour of emitted light is a function of the temperature of the object emitting the light (we are talking about hot temperatures like stars) So in terms of stars, the light from hotter (11,000 Kelvin +/-) stars is bluer (blue-white) and from cooler stars (3,000 Kelvin +/-) is reddish.  Our sun is in-between (6,000 Kelvin or so) and it so happens natural daylight is in the 5,500 to 6,000 Kelvin range.

With the white balance slider on ACR as an example, the colours look opposite to nature as you describe.  What is going on here (I believe and I am open to correction) is that when you are adjusting the white balance, you are ending up adjusting the colour to end up with a natural daylight colour/tint (ignoring valid reasons why you would not want to do this, creative reasons, sunrise/sunset light, etc.).

So if your camera, or white balance card is saying the temperature of the light the photo was taken is 3,500 Kelvin that is reddish light (remember how in old days you'd get back indoor shots from the drug-store film lab and they all looked yellow-brownish because of the incandescent lights?).  So to get back towards natural daylight in the photo you need to "add" blue (equivalent to subtracting yellow) to the picture.  So the seemingly opposite way the colours are shown relative to temperature seen above the ACR slider is just a way of representing visually what sliding the slider adds back into your photo.

Andrew

[hjscm]

Thank you for that. i was just wondering and that made sense to me.  was wondering why 20,000k was blue with my lights.


thanks
chris

In nature, the colour of emitted light is a function of the temperature of the object emitting the light (we are talking about hot temperatures like stars) So in terms of stars, the light from hotter (11,000 Kelvin +/-) stars is bluer (blue-white) and from cooler stars (3,000 Kelvin +/-) is reddish.  Our sun is in-between (6,000 Kelvin or so) and it so happens natural daylight is in the 5,500 to 6,000 Kelvin range.

With the white balance slider on ACR as an example, the colours look opposite to nature as you describe.  What is going on here (I believe and I am open to correction) is that when you are adjusting the white balance, you are ending up adjusting the colour to end up with a natural daylight colour/tint (ignoring valid reasons why you would not want to do this, creative reasons, sunrise/sunset light, etc.).

So if your camera, or white balance card is saying the temperature of the light the photo was taken is 3,500 Kelvin that is reddish light (remember how in old days you'd get back indoor shots from the drug-store film lab and they all looked yellow-brownish because of the incandescent lights?).  So to get back towards natural daylight in the photo you need to "add" blue (equivalent to subtracting yellow) to the picture.  So the seemingly opposite way the colours are shown relative to temperature seen above the ACR slider is just a way of representing visually what sliding the slider adds back into your photo.

Andrew

[Marco Ugolini]

OKay how come in photography when you adjust white balance lower numbers turns more blue and higher numbers turn yellow.  now for imstance my fish tank the lights are opposite.  lower temp is yellow and higher temp is more blue.

thanks
chris

Chris,

It's not different from the old analog days, when we had to place a filter in front of the lens, say, if we were using tungsten film to shoot in daylight.

If you were shooting a daylight scene without a filter while tungsten film was loaded in your camera, the resulting image would look too blue, because the tungsten film was color-balanced for a much yellower light. If you added a yellow-orange filter in front of the lens (a Wratten #85 or 85B, if memory serves) and also increased the exposure to compensate for the decreased amount of light hitting the film, then the scene's overall color would be aligned to the film's own color balance, and the tungsten film would no longer produce a blue cast: the image would look realistic, rather than color-casted.

Similarly, to go back to ACR, think of the image portrayed in your image as if it were the scene in front of that old analog camera, and think of the slider in ACR as if it were the film inside that old analog camera. If the scene is in daylight (let's say, 5000 Kelvin, for the sake of argument) but your slider is at 3000 Kelvin or so (roughly the correlated color temperature of tungsten light, or the color balance of tungsten film), the image in ACR will look too blue.

Quod erat demonstrandum.

I hope that helped.