someone who's been painting for a while .. can you explain how/ what the general principles are of turning the form with temperature only and no value shifts.
thanks in advance.
I'm not sure that it would be very effective to have no value shift. If you photograph your image and convert it to greyscale, it should still read as volumous form. If there were no value shift, it would read flat. Changing your temperature without at least a subtle shift in value would indicate a color shift on the surface of an object, but it would not describe the form of the object. Additionally, changing temperature without changing value is not an easy thing to do. Being that every color temperature is relative to those around it, value changes play a big role in our perception of warm and cool.
Sometimes you may want shifts in color to describe form with only subtle shifts in value (say, painting a young woman's face) because it can give a very soft apperance. Still, there are going to be shifts in value, slight though they may be.
I'm attaching a quick little example bellow. There are four boxes.
The first is a color field with shifts at either end which are of the same value but different hues. Note how, even in this color version, it reads as very flat, like a blank tv screen with discolored spots. The center may be warmer than the sides, but there doesn't seem to be much in the way of form.
The second is this same image saved as a grey scale. Now the image is completely flat, one solid tone.
The third is the same field of color as the first, but the edges now have definite value shifts as well as being different hues. There is a form, vague though it may be. Something like a detail on a piece of drapery.
The fourth is a greyscale version of the third image. Note how this also reads as an object with volume despite having no color or temperature.
Planes perpendicular to the line of vision are strongest in chroma and nuetralise as they turn away. Although as Dave has shown, doing this without shifting value as well gives you very little form. On the other hand, adding chromatic shifts to your edges on top of the value changes can make a dramatic difference.
Last edited by Elwell; January 2nd, 2007 at 03:26 PM.
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Dave, I think you've explained things really well, but I must say that your first image does give a slight impression of form because warm colors advance while cool colors recede. This impression disappears in the grayscale version, of course.
My painting teacher always said that if you couldn't turn the form using value, turn it using color. By this I always took him to mean that if there was something about the lighting that made it difficult to show volume with value (maybe the object was getting washed out on one side by the light, or conversely was too much in shadow?) then try using a change in color to indicate the plane change.
I suppose you can use colored lightsources and the brain might figure out which surface points where, if you're consistant. Shadow outdoors is often cold and light is warm, but then you also have speculars from the sky which could be cold but still pointing up. At any rate,the eye often assumes that cold is shadow and probably not reflecting towards the sun, so maybe that can be used to some extent.
You can also use an intermediate darker edge between the light and shadow to separate them, while having the light and shadow somewhat close to each other. It depends on whether there's any reflective light hitting the shadow but not the edge on of the shadow to the light.
Also, you can use texture and stroke direction to suggest wrapping.
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Dave thanks, very helpful
What your asking about is something that the Impressionistic painters used in they're work. You have to realize though that if you choose to show form through temperature shifts you are sacrificing contrast/values like the others here have said. Take a look at Mary Casett and Monet to get a feel of how they did it. Elwell makes a good point at combining the two styles for a more dynamic effect.