Types of Light, Cast Shadows & Perspective of Shadows

Types of Light, Cast Shadows & Perspective of Shadows

Greetings,  this week we will be continuing our discussion of Andrew Loomis’ book Successful Drawing, and considering types of light and how to represent shadow.

He begins by indicating that there are two main types of light.  These types are

  1. Direct light
  2. Indirect light

Loomis emphasizes that the decision to treat a scene or subject which an artist is attempting to represent, begins with choosing one or the other of these 2 types.  It is important to choose only one of these types, and to stick to it because the treatment of light in a drawing is what gives the art an impression of consistency.  The absence of light could technically also be a 3rd category, but Loomis doesn’t even mention it because the drawing would be pure black.  Any small amount of a subject matter, regardless of shadow depth around it, is an effect of Indirect Light treatment.

With the casting of light, comes the Cast Shadow.  Cast shadows are the areas of a drawing where your subject matter interferes with the direction of light, and that interruption shows on another plane in the form of a shadow.  The shadow you see of yourself on the ground on a bright day is a Cast Shadow.  This is different than the type of shadow called Shading; ie. how lights and darks fall on an object, as discussed previously. Although one could consider the Shading on the dark side of the moon, to be a shadow which is cast by its lit side, such  reasoning only confuses the issue.  It is better to think of Cast Shadows as those shadows which an object throws onto another plane or object.

  • Cast Shadows: the interruption of light caused by an object, translated as darker value, appearing on a secondary object.
  • Shading: the translation of how light falls on a specific form, related to that form’s general shape.

When representing Cast Shadows, the artist must consider 3 factors.  These factors are as follows:

  1. position of light source
  2. angle of light
  3. the Vanishing Point (VP) of the shadow on the horizon.

Each of these three must be understood in order to place a Cast Shadow convincingly within the context of the scene an artist is attempting to represent.  Loomis shows us how to do it.  He indicates the best way to cast the shadow properly is to alter the plane of your subject matter which is facing the light to a square.  Draw this square properly extending to the VP.  Then, using the line the light falls at, project a central line and lines from the corners to the angle of ground you have your subject matter sitting on.  This will show you how a square casts a shadow.

Example.  IMG_9277


Here are the steps.

  1.  Contour draw your actual subject matter with light pencil.  Decide where the light is hitting the object and the angle it is coming at.IMG_9269
  2.  Draw a line of the light direction, and approximate the “Illustrator’s Bump” (see last post) which will show at the transition from light to half tones.  The line of light will bisect the Bump.IMG_19270
  3. Draw a flat square shape, representing a simplification of the plane of your subject matter which is facing the light.  Set the square to the VP which your actual subject matter is related to.  Cast diagonals from corner to corner of your new square to reveal the centre.  I do this on a separate layer to keep the original artwork clean.  NB> the line of light is not related to the perspective lines.  They are at separate angles.IMG_9271
  4. Project the edge of the square onto the ground at the angle you imagine your subject matter to be sitting at.  This angle goes to the horizon again, at a secondary point, where the VP of the shadow points.  IMG_29274
  5. Cast a line parallel to your light line off of the top near corner of the square. Let it cross the angle line you drew in step 4.IMG_39274
  6. From the bottom near corner, send a line to the VP.  Likewise do the same from the point where  the top light line from step 5 bisects your ground angle.  Lines to VP are pink, Light lines are green. The pink perspective lines show you the top of the projected square.  IMG_19274
  7. Use the points of the square to draw the other side of the projected square, bisecting the top perspective line you just drew.   Aim this line to the VP of the shadow used in step 4. This line will establish the mostly hidden other side of the projected square. The yellow line represents the opposide edge of the projected square.IMG_y19274
  8. On another layer, draw lines from corner to corner on the projected square, and where they cross, draw a third dotted line parallel to either side.  That dotted line is the centre of your projected square.  These guides will help you draw the projected shadow of your original subject matter.IMG_9275
  9. Using this information you worked out, go back to your original contour drawing of the shape, and add the proper modelling of form in light, as well as the Cast Shadow laying on the ground beside. Don’t forget the Illustrator’s Bump, where the shaded side meets the lit side.


Next week, we will continue with some more information on how to use Cast Shadows in perspective.  Thank you very much for reading.






Light on Basic Forms II

Today, we shall continue the investigation of how Andrew Loomis unpacks the principles of light and its effect on forms.  Following the 4 Laws Loomis provides for us, as outlined in the previous posting, he continues with some very useful particulars regarding light and shadow.

The first of these particulars is the phenomena Loomis calls the “illustrator’s hump”, that is the observation of how on a curving surface, the darkest part of the shadow appears closest to the lightest part.

This seems counter intuitive, as per the idea that the furthest point away from the light source must be the darkest point, until one realizes that light also reflects. The darkest part shows at the point of change from light to dark, on account of the fact that a certain degree of the cast light reflects back from the surface which the lit object is laying on. This reflected light, or other ambient light partially illuminates the object.  This phenomena does not occur on the Moon, because the Heavenly Bodies are objects which are actually suspended in space, and there are no planes below them, which could reflect the light back onto the dark side.

A further observation about the ‘illustrator’s hump’ is that the shadow which the object casts begins where the “hump” on the surface begins.  Tracing a light line in the direction which the light is falling will show you where to put the edge of the shadow which the object casts on the plane it sits upon.  For clarity, please refer to the illustration I have done, just below.


illustrator's hump

Further particulars which Loomis outlines in this section are some rules on how to think of the principles of light and shadow in regards to the angle the subject sits at, relative to the light source.  If one thinks of angles, rather than the puzzles of how to render light on a surface, many potentially confusing traps can be avoided.  He provides us with the following principles.

  1. An object between the viewer and the light source is in full shadow.
  2. If the light is behind the viewer, the lit object is cast in full light, as in the effects of a flash bulb.
  3. If the lit object is placed at right angles to the viewer’s position, as well as to the light source, the object seems to be half in light and half in darkness.
  4. If the lit object is placed in a quarter-turned position, the resulting effect is either 3/4 light and 1/4 dark, or vice-versa.

Loomis further indicates that quarter turned positions present a more satisfactory effect, as either light or dark then dominates the subject matter.  This appears more appealing to the viewer than an equal division of light and dark.

Finally,  there is concession which Loomis gives to certain cases where an even dispersal of light on a subject is appropriate, for instance he indicates that full-frontal light is good for posters and poster effects, such as in the work of Norman Rockwell.

Thanks again for reading, next week we will cover the 2 main types of light, cast shadows and how to represent shadows properly in perspective.


Light on Basic Forms

The third main section of Successful Drawing deals with the techniques artists use when rendering  light and shadow on the basic forms. (Please see my previous postings regarding how illustrators simplify the many organic shapes in nature, down into a handful of basic geometric shapes.)  Here again, Loomis articulates a principle of representational art which is easily overlooked when an artist is attempting to represent a subject.  He states that light and shadow are the phenomena which delineate what we call form.  Furthermore, he reminds the reader that the entirety of the visible world is light falling on form.  What our eyes perceive as a shape, or colour is actually the effect of light striking a 3-dimensional mass.  Comic artists who work in line are sometimes forgetful of this truth. Although line is a fine method of describing light on form, too often does the line-based illustrator become fixated on the particularites of design when drawing, rather than acknowledging that perceived form is actually a phenomena of light.

Next, Loomis indicates that Nature is too complex for any artist to memorize or even attempt to fully translate into a piece of representational art.  He reaffirms the aforementioned concept of relying on a system in order to understand the infinite variables found in Nature.  Frankly stated, Loomis indicates that one must simplify light and form.

To warm his readers up to the concept of form being a phenomena of light, Andrew Loomis considers the heavenly bodies in the solar system, drawing attention to the general shape of such bodies -the sphere.  When one imagines the full moon on a very clear night, generally the shape pictured in the mind’s eye is a white circle.  Yet, if you really look at the moon, you will see that there is actually a gradation of bright white to light grey on the mass.   The section which appears brightest, is that area of the Moon’s surface which is at right-angles to the Sun.    As a short hand rule, one can consider the highlight as the shortest distance between the lit surface and the light source.  

This highlight curves around the face of the Moon, and diminishes in value to least amount of light, at a point 180 degrees opposite the highlight.  The shadow begins to form on the sphere where the light is at a tangent to the surface.  This phenomena of shadow always begins at the halfway point between the surface nearest to the light and the opposite face, which is furthest from the source.

Andrew Loomis provides for his readers a Set of Laws which can be pulled out as summative facts regarding Light on Form.

  1.  LIGHT TRAVELS IN A STRAIGHT LINE.  This Law shows why a single light source is not able to reach more than halfway around any round form.
  2. SURFACES ARE LIT AT ANGLES RELATIVE TO LIGHT.  This Law is meant to awaken the artist to the phenomena that any surface which is represented, is lighted according to the angle of its surface in relation to the direction of the light source.  When one begins to think in these terms, determining value is made accessible.
  3. RIGHT ANGLES ARE BRIGHTEST.  Planes which are fully flat appear brightest, and on curving shapes, that piece of surface area which is at 90 degrees to the light source likewise appears brightest.
  4. GRADATION = CURVING.  This law is easily forgotten when inventing value representation.  The curving plane is rendered with gradations of light to dark.  The flat plane is not.  The flat plane is lighted evenly, relative to its degree facing the light source.

This fourth Law is really the father of the others, and it is the secret of lighting.  To restate, flat planes are also flat in tone or value.  They appear even; even in colour and lacking variance.  Rounded masses on the other hand are described with modelling of value and gradation of tone.

Thank you for reading this week’s blog.  Next posting will go into a further consideration of the effects in value related to an object’s relative degree facing the light source.  See you in 7.