Define "Vibrancy" in more conventional color terms?

[Rob-F]

I'm trying to understand the Mac "vibrancy" control. I can see that advancing the slider makes many pictures prettier. I can see that to some extent it increases saturation, and so must have some overlap with that slider. But it also changes the color cast. In some shots it seems to change white balance. And often, it seems to add a sort of golden warm cast. This is just based on playing with a few images.

I'm wondering if it has some basis in basic color theory, or if it's some sort of "rose colored glasses" thing, like some of the Tiffen filters, like the 812 that pinks everything up a little, or the two-color polarizer that adds a little blue here and a little gold there.

Any ideas?

 

[antiquark]

In an image, colors are composed of red, green and blue components. So a dull red might be:

red = 200
green = 100
blue = 100
color sample here:
http://htmlhelp.com/cgi-bin/color.cgi?rgb=c86464

If you wanted to make it more vivid, you'd increase the red component, and decrease the green and blue parts. You'd have something like:

red = 220
green = 80
blue = 80
color sample here:
http://htmlhelp.com/cgi-bin/color.cgi?rgb=dc5050

That's a bit of a simplification, but saturation, hue, etc are all based on re-calculating the red, green, and blue components.

 

[remegius]

I'm not sure what you mean by the "Mac" vibrancy control, but I can tell you that in Adobe Camera Raw the vibrancy slider is a nonlinear saturation boost. Its algorithms are set so that it increases less saturated colors more than saturated colors, and leaves skin tones alone. This way you are much less likely to get the kind of saturation clipping that might occur when just using the saturation slider.

Cheers...

Rem

 

[Rob-F]

So it just diddles with the balance of RGB? That does seem to agree with what I see going on with the histogram when I move the slider. So it's nothing we can't do by playing with the RGB sliders? Nothing new under the sun, then--even though it does change the white balance.

 

[antiquark]

So it just diddles with the balance of RGB? That does seem to agree with what I see going on with the histogram when I move the slider. So it's nothing we can't do by playing with the RGB sliders? Nothing new under the sun, then--even though it does change the white balance.

Yes and no... it diddles with the RGB, but in a complicated way. Here's a page explaining the mathematics of saturation:

http://en.wikipedia.org/wiki/Saturation_(color_theory)

I think if you just adjusted the RGB sliders, you'd get a color cast, not more vividness.

 

[Rob-F]

Remegius: I'm referring to the Vibrancy slider in Apple Macintosh Aperture. Probably I should have said "Aperture" and not "Mac."

Thanks to both of you!

Rob

 

[gavinlg]

In both Aperture and Lightroom "vibrancy" increases saturation in a subtle way which has minimal effect on skin tones. So you'd use Saturation for landscapes, vibrancy for portraits in which you want more saturation. That's a basic explanation.

 

[JohnnyT]

The vibrancy slider don't push the color the way saturation does... It give you more saturation for the color that are less saturated without actually clipping those who are saturated. That way you see much less degradation than when you use the saturation slider.

I don't think only using it for portrait does the job... Because the way vibrancy works tend to be more "natural", maybe "filmic". You can actually use it for all your pictures.

In other words, it's less destructive ; especially if you work directly on the raw files like in camera raw. In a good workflow, you can push the image's saturation by sliding a little bit the saturation slider and more of the vibrancy slider; the same process could also goes backward.

Hope this help...