One of the most common problems encountered when attempting to render form and volume to a high-degree of finish is the impulse to excessively “follow” the form with application strokes. This “following-of-the-form” can sometimes be described as a stroke direction that dogmatically adheres to the direction of significant light dark separations, (value disparities), thus making particular stroke directions prominent throughout the value application process. While this is not necessarily a BAD thing–(as many may desire such stroke prominence this for a multitude of creative reasons)–you should be aware that such prominence is one of the main causes for noticeable skips or breaks in value gradations that are intended to be seamless gradations.
This is one of those cases where novice intuition may lead the artist in the direction directly opposite of his or her goal.
It is important to remember that an effective and efficient path to both form and finish (where a multi-layer, dry-media application is concerned) is stroke-direction variation. Let’s look at how stroke prominence is contributing to the appearance of value “banding” in this sphere study–and how variations in stroke direction can alleviate it.
In the above illustration (top 3 spheres) we can find such breaks. The manner in which these ‘breaks’ occur is a tell-tale sign that application strokes followed the attached shadow accent (i.e., terminator, core shadow) for the most part. The structural "anatomy " of the sphere is correct—but the breaks in gradation (exaggerated by the third sphere illustration above) can interrupt our perception of the form (remember, our fixations are drawn not to slow, gradual changes in value—but to sharp, often-infomration-bearing disparities ). Below the top three sphere illustrations you can see an illustration of the sphere drawn for the Language of Drawing DVDs and a recreation of the multitude of stroke directions that led to the finished rendering of the form. Keep this concept in mind when adding value. Vary stroke direction as much as possible (again—as long as it is not violating an aesthetic you are pursuing) and you will find your value gradation ‘breaks’ becoming a thing of the past.