The ONLY thing left that I am struggling with...picking colors...

[smackcakes]

Perhaps the place to look is in your science books under visible light?

Essentially visible light can be divided into different wavelengths which we call colours. For an object to be visible to us its surface must reflect some or all of those wavelengths. Some surfaces only reflect certain wavelengths and absorb others which is why they look coloured.

For example: A Green object only reflects Green light (or more accurately Blue and Yellow light) it absorbs Red light. So it follows that if you shine a red light on the object then the light will be absorbed and the object will appear black.

How about if we shine an Orange light on the Green object? Orange light is composed of Red light and Yellow light. The Green object reflects Yellow light and Blue light and absorbs Red. Since the Orange light contains no Blue... none can be reflected. The only colour that can be reflected is Yellow. So the Green object will appear Yellow.

A Blue object under a Green light will probably still look Blue.

Of course it's not quite that simple, there is no guarantee that a Green light contains every shade of Blue. Many Blues also contain traces of Red, which won't be visible under Green light, so the colour may shift to a different Blue.

You also have to think about saturation. A very desaturated or pale object will be largely Grey/White so it will reflect all colours somewhat (despite it's hue). A very saturated object will only reflect specific wavelengths.

Of course most coloured lights still contain a fair amount of white light, so often objects will only appear slightly tinted, or slightly dulled.

As for shade and saturation etc... That really depends on the surface. Most surfaces tend to become less saturated the more they are shaded. However metals and very reflective surfaces tend to have quite saturated shadows and washed out mid tones.

[rluto77]

Wow that was very useful. So basically, the shades of color that appear on an object when lights of various color are shining upon it depends on the wavelengths that the objects color absorb and the color of the light.

Is their a book that explains all of the colors and all of the ways that light interact with them (absorbed wavelenths, etc)?

I'm talking something that is very in depth so I can have a reference to go to when painting. Or even a website (so far I haven't been able to find one).

[smackcakes]

I haven't personally read any books specifically about this, so it would be difficult for me to recommend one. But it's fairly easy to work out if you know your colour theory ie. Primary, secondary and tertiary colours.

The only difference is when dealing with light the primary colours change because you are adding light rather than subtracting it. The wikipedia page on primary colours explains a little about this.

http://en.wikipedia.org/wiki/Primary_color

There are other issues too, such as luminance, certain colours don't work as lights (ever see a brown laser?). The wiki page on colour theory explains a little of this.

http://en.wikipedia.org/wiki/Color_theory

But if you are looking for a specific reference, then the easiest thing is probably to make your own. Taking an ordinary colour wheel into Photoshop and placing a layer of pure colour over it, set to 'multiply' will show you your available spectrum under that light.

Here is an example:

http://i103.photobucket.com/albums/m134/SmackCakes/colourwheels.jpg

The wheel on the left is a standard colour wheel under a perfect white light.

The wheel in the middle is the same colour wheel, only this time under a duller orange light, like a 40 watt bulb. Pure white is no longer available because there was no pure white light to begin with, however the white portion of the wheel reflects all the available light there is. This shows you the colour of the light (dull orange). The other colours are largely the same, just with blue and green fading a bit.

If you want to make your own, you have imagine what colour a piece of white paper would be under your light (kind of the opposite to white balancing on a camera). That will give you the colour to multiply over your colour wheel.

The wheel on the far right, shows the colours under a pure red light, like in a dark room or a submarine. Obviously blue and green now appear black. Yellow and magenta are visible but only reflect their red component. White reflects all available light, in this case all the light is red, so the white area appears pure red.

[rluto77]

I really cant thank you enough. Its already starting to make sense. Now the only thing I really don't understand is how some of these artists figure out the perfect color to use for something on the fly :)

I really appreciate it. I guess what I could do is use that color wheel, figure out the colors of the lights in the scene I'm painting, and just set a few of those up using multiply.

One quick question. I am currently painting a fantasy scene and decided to make it take place at night. I simply added a multiply layer of a dark blue set at low transparency. It worked really good and it looks very natural.

Would this essentially work for any scene I do? As in, can I paint a scene not taking into account the color of the light sources (just the direction and intensity of the light) and then just do overlays???

[smackcakes]

To be honest I don't think most artist do pick out the 'perfect' colour on the fly. You just learn your theory as best you can, and then give it your best guess. The same goes for shading and anatomy. Computers can ray-trace a scene and tell you exactly where the shadows should be with mathematical precision. People can't do that, they just have to approximate. It doesn't have to be perfect it just has to be believable (this is where references help). Remember... no one is going to be comparing your painting to a photograph to check that you got the shadows pixel perfect (unless it stands out as obviously wrong)

It might sound at first like humans are inferior to computers in this respect, but actually not being limited by what is physically 'correct' can be a big advantage. A lot of times artist will take a photo or render a scene in 3D and then take it into Photoshop and add some extra shadows. Should these shadows be there? Who cares? What matters at the end of the day is if it looks good.

As for putting layers over an actual scene... The technique I descried above won't work properly for that. Adding a multiply layer over a regular scene will probably darken the image too much. I would suggest setting the blend mode to 'colour' or 'overlay' (at lowered opacity of course) if you want to tint a whole scene with an ambient light.

Colour and overlay won't give you mathematically perfect colours... But they get you reasonable close. I do this quite a lot. Adding a subtle tint of colour over a picture can help to tie all the other colours together and unify the image. It can also help you suggest the mood of your picture. For instance you can tint everything slightly blue to make the picture appear cold and moody. Or tint everything yellow to make it feel warm and comforting.

Colours are a very powerful medium in their own right, and can provoke a very deep emotional response. A great artist is not someone who paints everything the right colour, but someone who uses colour to enhance the massage their picture is trying to convey.

[Lunatique]

I tend to do two things when I try to figure out complex color situations such as a colored light source on a different color, which also has some of another different colored light on it.

Keep in mind, this is just my way of thinking, and it's not any kind of rule and may not be correct. I usually think along these lines:

Local neutral - The original unaffected color of the object under neutral lighting. So let's say it's yellow plastic cup.
Light source color - The color of the light source that will shine on the object. For example, a tungsten lamp is roughly amber in tone.
Any other light source color - If you have another colored light source nearby that will also reach the object. For example, the TV is displaying a scene of blue sky with no clouds, so the screen is illuminated with a sky blue color.
Surface property of the object - If it's made of shiny or matte material, or if it's transluscent...etc.

So let's say the lamp is shining amber on the yellow cup. The result in my mind will look like if the amber was has mixed with the yellow at the point of the terminator, almost in equal amounts, but towards the highlight where the angle of the cup's curvature will probably show value/color that contains more of the amber and less of the yellow (because plastic is somewhat reflective), and this is particularly true is the actual light bulb of the lamp is reflected.

Then the blue light on the TV will tint the cup as well, and depending on where the TV is placed in relation to the cup and the lamp, the amount of blue showing on the cup with vary. If it's place on the opposite side of the lamp with the cup in-between, then the side not lit by the lamp will be mostly lit by the blue, so I would say at that side, the terminator will be a mixture of blue and yellow (green), and towards the outer edge, it'll be mostly blue and less yellow (reflective surface once again).

If the TV is in front of the cup and the lamp is to the left of the cup, they will both be affecting the cup at the terminator at about the 7:30 position, and I'm guessing it'll be an equal mixture of amber, yellow, and blue. Then at the 6:00 position, the cup will be mostly blue (this is assuming the TV is fairly close and bright, otherwise, it'll be a varying degree of blue mixed with yellow, depending on the distance and brightness of the TV), and at the 9:00 position, the cup will be mostly amber, with a little of yellow (once again, distance and brightness will vary that).

So I guess with that, you can see how my mindset works when thinking about colors and colored lights in a scene.

Now, that's only the first part, and it's the unscientific part, as I'm only guessing based on my experience and knowledge, and since I don't have a Phd in physics, I'm pretty sure it's not totally correct. So I'll need to check against my assumptions by doing an actual scientific test--photography with real lights and objects. I usually only do this if I'm really stomped, otherwise I don't bother and if it looks good, then I'm ok with it. I'm an advocate of "aesthetics before accuracy when you're pushed to make a decision."

So with my 2nd approach, I'll actually put a yellow cup (or something similar) on a table, kill all the lights except the two lights I want in the scene--a typical household lamp with an amber tone output, and a TV with the screen set to a blue sky scene. Then, I take a photo (make sure your white balance setting is set to a neutral one, such as a bright day setting, since the sun at noon is roughly what camera manufacturers use as the standard).

That's it. With that photo (and whatever observations I make during the experiment, such as walking around the setup to observe how the two lights affect the cup at different angles, and how they interact if I move the lights/cup around), I can now check it against my previous guesstimation and see if I was way off the mark or pretty close. And this new found knowledge will help me in the future by setting me on the right kind of guessing based on newly acquired scientific data. (And of course the previously mentioned stuff like different color wavelengths will also help your understanding.)

You can also try it in 3D if you know rendering well and are confident you'd get a pretty accurate result that's almost identical to real life (or reasonably close for the purpose of an artwork).

BTW, the way I often pick a color is first block in all the local colors in their neutral state. Then, I pick the color of the light source, and then lightly paint over the area it's supposed to illuminate with just one small stroke, and depending on how close or intense the light source is, I'll exert different pressure with the tablet pen. Then I'll use the eye dropper tool on that small stroke because it now contains both colors--about the mixture I want. I'll then proceed to paint the lit area with that color. I'll then do the same for other light sources. If things get complex like multiple colored light source on one area, I'll have to do it for all the light sources on the same spot and then sample that spot's color. Of course, this is not scientific so use it in conjunction with your scientific experiments and studies about light and color.

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