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Creative Illustration: The Form Principle

Updated: Jun 21

This is the first part in an ongoing series on Andrew Loomis’ book Creative Illustration

I was recently looking through our art book collection and came across “Creative Illustration” by Andrew Loomis. Most professional artists and students are somewhat familiar with Loomis’ books, particularly those on figure drawing, but this book is not often discussed. I recall having skimmed through it once in the past but now, while looking over it more attentively, I realize that it is a really marvelous book and extremely valuable. It’s full of incisive and critical information on the subject of image-making and contains very detailed explanations of especially difficult topics like values and composition. 

I’ve been inspired to write a series of blog posts about the sections which I’ve found most impactful and summarize the highlights, along with some of my own thoughts. I encourage anyone who wants to know more to pick up a copy of the book for themselves.

Photo of the book Creative Illustration by Andrew Loomis
Our copy of Creative Illustration by Andrew Loomis

Understanding the Form Principle

Starting with the Introduction, we are immediately presented with memorable quotes on the subject of form and light. 

“The Form Principle is the rendering of form as to its aspect at any given moment with regard to its lighting, its structure and texture together with its true relationship to its environment.”

“It must be determined at once what kind of light we are working with for its nature, quality and the direction from which it comes will affect the entire appearance of the form.”

This ties in to something we frequently mention to students in our digital art classes: decide on what kind of light you want in your scene before you begin painting it. It is virtually impossible to create any kind of consistent render if you don’t even know how you’re lighting your own scene. 

“The lightest areas of form will be within those planes lying most nearly at right angles to the direction of the light. The halftone planes will be those obliquely situated to the direction of the light. The shadow planes will be those planes lying in or beyond the direction of light so that the light of the original source cannot reach them. The cast shadows are the result of the light having been intercepted, and the shape of such intercepting form is projected to other planes. In diffused light there is little or no cast shadow. In brilliant light or direct light there is always cast shadow.”

In Summary

  • Value range in direct light = wider

  • Value range in diffused light = narrower

To this we should add another perhaps obvious point about the cast shadow- that the value of a cast shadow is determined by the value of the object that it is projected onto, not by the value of the object that projects it.

“Direct light produces much more reflected light, and this is most apparent within the shadow. The amount of reflected light reaching the shadow will determine its value. Everything upon which the light falls becomes a secondary source of reflected light and will light shadow planes in the same manner as the original source, being brightest on the planes at right angles to such reflected light.”

“...reflected light can never be as light as the original source. Therefore, no area in the shadow can be as light as the areas in the light.”

According to Creative Illustration this is the single biggest reason images fail and it is something we see time and time again in student work, that is, failure to keep the values in shadowed areas separate from the values in the lit areas.

“Both light and shadow areas must be simplified and painted in the fewest possible values. The object is to make all the lit areas hold together as one group, as opposed to the shadow areas as another group.”

Also known as “grouping your values”. This is the essence of the Notan, a Japanese concept of light and dark harmony.

Illustration of two men and a woman at a table
Mead Shaeffer

Consistent Lighting and Value Relationships

“All forms within your picture should appear to be lit by the same source and be lit consistently with one another.” 

This holds true whether the light is natural or artificial, single or multiple light sources. According to Loomis there is only one way to get this right: by direct observation from real life. Of course, now in the age of 3D software it may be possible to create a realistic render of a lighting scenario digitally, but I am of the opinion that in order to set that up and simulate it convincingly, the 3D artist would still need to have some benchmark to work from based on the observation of reality. 

“All things represented within a given light bear a relationship of tone and value to one another.”

What this means is that every object in a scene has its own base value (local value) and different colored objects have different base values from one another. The key is, those differences have to be maintained regardless of the lighting scenario. Therefore,

“..bright light can raise the value, and dim light can lower it. But the light raises or lowers all other surrounding values correspondingly, so that the value of the subject holds a constant relationship to other values. It will remain in any light, so much lighter or darker than its neighbors.”

To further explain this, let’s look at another Mead Shaeffer piece, in particular, the man’s jacket and pants. The pants are a lighter value (let’s say off-white) and his jacket is a brownish color, so a darker value. In any light, this relationship will remain. Whether they are in bright light or in deep shadow, the value difference between them (the relationship) cannot change. We can raise both, or lower both, but we must maintain the difference. Let’s compare the values in the light and shadows to verify this.

Illustration of a man and woman with callouts
Mead Shaeffer

Practical Techniques for Illustration

A good way to develop the form and make sure you’re keeping your values intact in your own art is to use Scott Robertson’s “Halfway to Black'' method, as it not only avoids the use of pure black in the shadows, but also maintains the relationship between objects of different base values. This is especially easy to do digitally by painting shadows in black on a multiply layer set to around 30% opacity.

Illustrated diagram of values and shading
Example of Halfway to Black

This is something students frequently overlook, they allow objects with very different base values to become the same value in the shadow side which breaks the relationship.

It’s important to remember, however, that the “Halfway to Black” rule mainly applies to full sunlight and strong artificial light scenarios, and not to every lighting situation (we’ll go into more of this in a future post on tone).

“Relationship of values is more correct in natural light than in any other.” 

An interesting note on this is the frequent attempt (in fantasy illustration) to use colored magic as a significant light source. It has a tendency to confuse or break the visual understanding of the forms. Below is a very successful approach to this situation in which Kieran Yanner circumvents this problem and maintains the strength of his forms by using one primary light source, a natural top-down light which reveals the forms of the figure with the magic “lights” acting only as secondary fill or bounce lights. Even though the magic light strands illuminate various planes on his figure, none of the shadow areas are allowed to compete in bright with the lit planes from the main top-down light.

Illustration of a mage casting magic
Kieran Yanner

“The big form makes the subject carry and appear solid, not the incidental surface forms.”

In other words, small shapes and surface texture do not do the heavy lifting in an image. They don’t carry the form and if over indulged and not subdued, they will break it. 

An example of this can be seen below in which the same subject painted with excessive small folds that muddy the forms can be compared to a version with clear folds that support the form. The effectiveness of the second image is easy to see. 

Art comparison of a woman sitting on a box
Details disruptive to the form vs form accentuating details

“Light and shadow in itself produces design. Value relationships between objects produce design.”

Now we get to the first of the real complexities in image-crafting: staging the image in a way which combines objects with different values, dimensions and shadow shapes, and positioning and overlapping them in ways which produce interesting arrangements. This is the abstract core of composition. Once we understand this, we can start framing and staging with narrative intent by using the arrangement and choice of values, shapes, contrast, and hierarchy to communicate. Not only this but we must also create these arrangements without breaking other rules like perspective and anatomy, but we’ll get more into that in a future post. Perceiving the compositional shape-based part of this becomes largely intuitive over time. 

Color vs black-and-white art comparison of Frazetta painting
Frank Frazetta
Color vs black-and-white art comparison of painting of an orange
Adam Clague

“The darkest part of the shadow appears nearest the light, between the halftone of the light and the reflected light within the shadow.” 

This is the ridge or “core” shadow. Where we choose to place this ridge and (therefore our light and shadow groups) will determine the design, look and feel of our subject and of the image overall. Not all placements are pleasing or effective towards communicating a specific mood so we have to be deliberate.

Collection of lighting reference photos of woman portrait

“The fundamentals are the same in all mediums.”

Loomis closes the chapter with this last truth, it’s not the brush that makes the artist. Fundamental principles are applicable to all mediums, and those who specialize in one medium will find that their skills are transferable if they switch to another. The only difference is in the physical properties of the materials and learning the specific ways in each medium to achieve a hard edge, soft edge, halftone, shadow, etc. 

We do dozens of portfolio reviews every year (hundreds to date) and it's amazing to me that so many artists are struggling with things Andrew Loomis solved and wrote about over 70 years ago in this book. This one chapter alone addresses so many of the most common problems! It’s really worth picking up and studying. Of course, it’s important to note that rules exist to give us a framework, once we understand them, we can bend them in order to achieve deliberate and desired results. 

I hope you’ve found this article interesting and useful. Next week, we’ll continue through Creative Illustration as Loomis goes into Line and Composition. 

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