Although one has to deal with a limited value range while drawing on paper, there are ways to manipulate the medium of graphite to better represent an objects' local color. My instructor, Jeremy Deck, has recently informed me of a way to represent an object's local color with the limited medium of graphite. This post is an explanation of my understanding of that process. Footnotes are included in this post to indicate which sentences in this post are summarizations of ideas that Jeremy Deck has explained to me.
By specifying three modeling factors I have been able to better represent the local color of the forms that I see. These factors include, the value of the highest form light, the distance of the halftone before the terminator and the value of the shadow.¹
The example above (on the left), represents a sphere with a white local color under much light. The high form light has been set at white of the paper, the shadow value has been set at a visual average of the shadow value observed and the small distance of the halftone has been pushed very close to the terminator. By making the distance of the halftone small and very close to the terminator, the drawing seems to represent a light local color under a lot of light.¹
The example above (on the right), represents a sphere with a slightly grey local color under a decent amount of light. The high form light has been set at white of the paper and the shadow value is also set at a visual average. The only difference in the modeling factors between this sphere and the one on the left is that the distance of the halftone before the terminator is slightly larger. According to Jeremy Deck, the smaller the distance of the halftone before the terminator, the more a drawing represents a form with a lighter local color under much light.¹ I imagine, and it would depend on the situation, that the darker a local color to be represented the more the value of the high form light would have to darken from white of the paper.
In conclusion, I am not prescribing a formula for representing the local color of objects, this is only one of many ways to represent the local color of an object in graphite. Rather, I am just sharing how this process has allowed me to better represent the local color of the objects that I draw. I would like to know how the science of how the eye percieves light can inform one's process for representing the local color of an object as well. If anyone is willing to share information on this topic with me please let me know.
*Blog Note- Some of you may have noticed that the information in this post has changed from its original post on 11/17/13. I have found that my explanation did not follow the laws of physics and had to update it. I apologize for the incorrect information in the original post. I am still trying to comprehend how the eye processes light and how that effects the way a local color is perceived. As well as a better way to represent the local color of the forms I draw. If anyone would like to share some insight with me please let me know.
¹ Jeremy Deck, personal communication, 2013.