TERMS TO KNOW

• HSV - Three dimensions of light, Hue, Saturation and Value. Can be viewed as a cylinderwith Circumference, Radius and Height.
• RGB - Three dimensions of light, Red, Green and Blue. I prefer to paint using RGB sliders because it allows me to easily add or subtract colors. If I have a gray, 120, 120, 120, and want to add some orange I might adjust like 120+30, 120+16, 120+2.
• Exposure - Just like the eye, a camera is a device which catches photons. When it saves an image it saves photon count per 'pixel'. When an image is converted to a flat canvas which isn't luminescent enough to shine like the sun, light values has to be cropped on the dark and bright ends. Cameras can actually save images in a format called RAW which does not crop away values (say, over 255). These images can be viewed on a 'High Dynamic Range' monitor which is capable of emitting brighter light than a regular monitor. When we paint on regular surfaces, the inability to portray bright things is forcing us to resort to various tricks which somewhat emulate brightness. Anders Zorn was excellent at this.
• Hue - Variations in color. Skin has some hue variation, such as cheeks being rosy. Even if an object is a single flat color, it can still vary in hue because it's subject to colored light and shadow, reflections and other effects.
• Saturation - How much color there is. Grays aren't saturated. Neon colors are very saturated. In the 8 bit RGB color model (0-255 per slider) you can measure saturation by looking at the difference between the sliders (min-max). Dark and bright colors look less saturated because it's not possible to bring the sliders far apart. For example, 255, 0, 0 is very red. 255, 220, 220, while full red, looks less saturated because the delta is just 255-220 = 35 and not 255 like in the former case.
• Value, Brightness, Darkness - There are several ways to calculate value. In the RGB color model, Green is the brightest, then Red, then Blue (i.e. 0, 255, 0 is brighter than 0, 0, 255). In a program I wrote once, I used the following common formula to calculate value from RGB: Value= (0.299 * Red) + (0.587 * Green) + (0.114 * Blue). If an artist praises a painting for its "great values", he probably means that, color choices disregarded, the painting is effective in the way it uses contrast to convey forms and make things read well.
• Read, Readable - You can tell what something is supposed to be, what is described. If a painting is messy, it's difficult to read.
• Radiosity, Ambience and Reflected light - When light is reflected of a surface and then hits something else. This happens all the time. In a green room everything will get a green hue for example. Radiosity is a 3D rendering term. I use 'reflected light' for sources I can trace, and 'ambience' when the color is some sort of average of lots of things in the surrounding environment.
• Speculars - Dots of light that appear on glossy or wet surfaces. It's really a mirror image of the light source that you're seeing. On more dull materials, light is perhaps broken up by very small bumps, so you won't see the specular dot moving as you shift your position. The lighting on the surface will look almost the same from different directions. A mirror is so smooth and reflective that light comes back almost undistorted from the reflective surface.
• Flatten - Removing unnecessary texture and values.
• Texture, Noise - Tiny details, sometimes repeating patterns, which sometimes used to show the material of surfaces, or just to provide interesting contrast and flavor. Photo models can look strange if they've been airbrushed so heavily that the skin texture has disappeared and looks alien. You can do neat things with texture, such as alternating a warm and dark color. This makes the average color of the texture appear more... dimensional and rich than simple flat surface would. Texture is a tricky beast to wrestle with, because sometimes texture will make a surface look too noisy, such as a tree crown, grass, or a brick wall. In such cases it's common to just partly suggest the texture.
• Form, Modeling, Sculpting - The 3D shape of something. Values are important when
• Plane - I don't quite know. I use it for Foreground, Middleground and Background sometimes, i.e. the 'BG plane'. In some cases I might mean the same as flat surface.
• Atmospheric perspective - Air is not fully transparent. As you may have noticed, things far away tend to fade away and sometimes shift towards a sky blue color. Atmospheric perspective can be used to visually separate intersecting parts at different distances. It can also be exaggerated. Some artists (including me) use atmospheric perspective on pinups to help separate limbs crossing each other (and also to fade the figure into the white background).
• Local color - I think this refers to the color an object has when viewed under neutral lighting conditions. In reality, things rarely show their local color because there's so much colored light bouncing going on. Kids can be excessive in their use of local colors. Green and brown trees, pink people, etc.