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In Adobe Photoshop Lightroom (c) there's a Temp slider which controls the color temperature of the photo. To the left it creates a blue, cold looking image. To the right, an orange, warm image.

This is easy to understand and easy to use.

But then is the "Tint" slider. To one side, it creates a purple image. To the other, a violet image. I really don't understand the purpose of this slider.

When I use it, I feel like I'm using the tint slider on an old NTSC television. What's the point of having a violet/purple image? How can I use it to improve my images? When I can't get the color right in my photos, I set the program to AWB and then tweak the temp slider, but I never touch the Tint one.

How do you use it?

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I recommend to read that book on the topic of LAB color space and color perception and what those two sliders do: amazon.com/Photoshop-LAB-Color-Adventures-Colorspace/dp/… –  Mart Oruaas Jun 15 '11 at 12:09
    
A very concrete example of when to use it: You use the colour picker, and the result is "correct" but dull. You adjust the blue/yellow slider to bring back the warmth of an evening sun – looks nice, except that you have introduced a little bit of ugly green cast in the blue sky. Then you can tweak the magenta/green slider slightly towards magenta to fix that. –  Jukka Suomela Jun 16 '11 at 17:57
    
@Jukka Cool!, will definitely try it. –  Andres Jun 16 '11 at 18:02

1 Answer 1

up vote 19 down vote accepted

The tint slider takes care of a couple things. First off, from a color perception standpoint, there are two major axes that the cones of our eyes base color perception on: blue/yellow and magenta/green. There are some specific nuances related to these axes, however the most important is that they represent opposite colors that the human eye can not see simultaneously at any given single point (i.e. you can't see blue and yellow at the same location point...the eye oscillates between the two....however you could see blue and or green.) Most color calculations that involve human perception are done in L*a*b* space, which is fundamentally based on those two axes of color.

When it comes to the blue/yellow axis, this happens to be the primary axis along with white point falls. White point is a critical component of color balance, and is generally why we make color temperature adjustments far more frequently than we do tint adjustments. This is partly due to the kinds of illumination we normally use to light photographic scenes as well. Sunlight, incandescent lighting, and a considerable amount of photographic artificial lighting is achieved via black-body emission lighting...matter heated to the point of emitting light. Such lighting usually emits light along the blue/yellow axis, rather than the green/magenta axis.

Another form of lighting, gas-emission lighting, usually emits light more in line with the green/magenta axis. Gas-emission lighting is usually found in fluorescent lights, neon lighting, etc. Scenes photographed under gas-emission lighting will usually take on a greenish or slightly magenta-tinged appearance (at the best of times), or may end up with a more aberrant appearance. The Tint slider in Lightroom is a way to correct for "off-axis" color balance issues often caused by gas-emission lighting or any form of non-standard (blackbody) lighting.

Generally speaking, color balance corrections will be done primarily with the Color Temperature slider, with minor adjustments to the Tint slider. Alternatively, the color temperature and tint sliders can be used to accomplish artistic effect, adding a strong color cast to your photos when one is absent. You may have a scene that is slightly purple-tinged, and one can enhance the artistic appearance of that purple tinge by making a larger-than-normal tint adjustment towards magenta.

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You blew my mind with the blue/yellow oscillating thingy. –  Andres Jun 14 '11 at 2:22
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@Andres: Kind of wild, ain't it? You never really realize the nature of vision until you try out a test like that. ;) You would get the same thing trying to view green and magenta at the same time in the same place. –  jrista Jun 14 '11 at 2:23
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Oh, I guess I did not address your final question, about getting white balance correct. My recommendation...rather than manually tweak the sliders, is to use the little color picker (eye dropper) control next to the sliders. Click the button, then find a "neutral" pixel in your photo...either a pixel that should be "white", or something that is as close to that as you can find. Click the pixel, and LR should correct temp and tint for you, making the pixel you clicked completely white-balance neutral. –  jrista Jun 14 '11 at 3:38
    
Yes, that's what I do. I use the AWB as a starting point, and then tweak the temperature until I like the results. –  Andres Jun 15 '11 at 3:38
    
the problem is the physically correct colours (white/grey = x,x,x) is rarely the most beautiful, and sometimes you dont have a grey/white area in your photo. –  Michael Nielsen Aug 27 '13 at 20:50

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