Color Light Theory

[AndreasHusballe]

Hi everybody
Im new to this forum, so I hope that it is the right place im posting. My question goes out to everybody who thinks that light is max interesting aka the shit :)
I have attached something that I have been struggeling with. What do you do in Photoshop when light, of a specific color, blends with a local color on an object? And, sould I apply ambient to the saded areas only? I have drawn my approach, but im not sure that it is the bedst...
Please enlighten me :)

[jubjubjedi]

There's actually a really good DVD tutorial from the Workshop called "Practical Light and Color" that I suggest for those that are struggling with color, as I often am. I can't recommend this DVD enough.

http://www.thegnomonworkshop.com/dvds/jvi01.html

[thinairart]

There is a sticky on the top of this forum that I think you will find very informative: The Dimensions of Color (http://conceptart.org/forums/showthread.php?t=112049)

[briggsy@ashtons]

Colours of light sources and surfaces interact following the rules of subtractive mixing (http://www.huevaluechroma.com/051.php: Figure 5.2). Your main light source is close in hue though a bit less green than your olive surface, so it will tend to boost saturation, and shift the hue towards yellow. Your secondary light source (H = 250) is basically complementary to the local colour of your surface (H = 74), so it will tend to desaturate without changing hue much.

The hue shift I just described for the main light source will be seen most strongly in the shadow of the secondary light source, and vice versa. Elsewhere, where both light sources are operating, you will see intermediate effects, varying with the relative strength of the two sources.

I find I can create these effects in Photoshop CS2 quite accurately (see attachments) by (1) painting the light distributions associated with each source independently on separate layers in screen mode, and then (2) applying the local colour (or colour patterns) using an overlying layer in multiply mode.

If that DVD is the one where the guy has a theory that saturation is usually higher in shadow areas than lit areas then caveat emptor!

[PieterV]

the guy has a theory that saturation is usually higher in shadow areas than lit areas then caveat emptor!

I actually was a little confused about this a while back as I was sampling colours for a underexposed photograph and the shadowy areas had freakishly high saturation levels. I concluded that that's because of image noise you get when taking a photo digitally, even when you even it out I still found pretty high saturation levels (above 50%). (I still haven't fully read all the colour theory you wrote so sorry if that's described somewhere)

[AndreasHusballe]

Im so much thanking you all for your replies!!! I have been reading a lot on The Dimension of color and it is really good reading! Come to think about it, I know a lot of the basic color theory, but I need the "how to get it down on photoshop" Do you guys start with a basic light/shadow on a surface and then build detail onto it? Im having a hard time with surfaces that are many colors.. Do you use layers or..? Any hint would be great and an explanitory picture like briggsy@ashtons's would be rewarded with a big kiss on the cheek ;)

[briggsy@ashtons]

I actually was a little confused about this a while back as I was sampling colours for a underexposed photograph and the shadowy areas had freakishly high saturation levels. I concluded that that's because of image noise you get when taking a photo digitally, even when you even it out I still found pretty high saturation levels (above 50%).

Another very prevalent factor is "clipping" of colours in the lighter areas due to overexposure. It's really just not a great idea to build a theory on colour picking from photos. In nature the saturation in the shadows may be greater or less (see attachments above) or the same as the body colour saturation in the light, depending on the relationships of the colours of the lights to the local colour of the surface. Even in the DVD that I saw the "rule" didn't seem to work half the time.

Andreas, a section on "how to get it down on photoshop" is my next intended project for the site so stay tuned. There is already a little bit about dealing with multicoloured surfaces (see link on the second page of my colour theory discussion thread (http://www.conceptart.org/forums/showthread.php?t=112049), which I've been neglecting terribly lately - sorry!). I'll be adding more there very soon.