"The Calling of Saint Matthew", Contarelli Chapel, Chiesa Di San Luigi Dei Francesi, Rome

Photograph Copyright ©2012 Loo Yen Yeo. All Rights Reserved.

Concepts: Chiaroscuro (Emphasising outline); Chiaroscuro (Secondary patterns); Exposure (High contrast)

Description: In "The Calling of Saint Matthew", Jesus (far right) calls upon Matthew, then Levi the tax collector (central figure behind the table), much to the surprise of the gathered.  This painting is a fabulous exemplar of Caravaggio's use of light.in defining and emphasising the use of outline. The high contrast is used compositionally in directing the viewer's gaze - a similar effect can be achieved with the control of exposure (also to high contrast) in photography. Notice also the shaft of actual light coming into the chapel from above; a secondary reinforcement to the primary shaft in the painting.

Title: --

04.01 Chiaroscuro

Chiaroscuro is an Italian expression which can be translated literally as "light-dark" and arose out of its use in painting - where subjects in dark scenes were dramatically illuminated using shafts of light. Chiaroscuro, as an approach, is an effective means of providing the contrast essential to good composition where it:

1. establishes tonal relationships;
2. conveys dimensionality;
3. determines compositional structure; and
4. highlights areas of visual importance

Johannes Itten described chiaroscuro as "one of the most expressive and important means of composition" [in "The Photographer's Eye" by Michael Freeman (2007), page 110]. Compositional devices involving the application of chiaroscuro include:

• crating ambiguity
• emphasising outline
• formation of primary patterns through caustics (i.e. reflected or refracted patterns of light)
• reinforcement of secondary patterns e.g. sunlight dappling an already-dappled forest floor

03.16 Exposure

Exposure, the amount of light allowed to impact photosensitive material for photographic reproduction, is often perceived to have a 'correct' role. There is an element of truth in this perception because of the technical limits set by:

1. what is visible;
2. the range of sensitivity of the photo-receptive medium (film or photo-sensor); and
3. the expected appearance of the subject.

However, 'correctness' is modulated by the aesthetic considerations which do impact on how the technical boundaries are interpreted, for example: an over-exposed bleached look, or an under-exposed saturated image. The artistic interpretation of light is fundamental to the visual arts, and a solid understanding of the properties of light interpretation is core to the artist.

Exposure can concentrate or diffuse attention
The viewer's eye gravitates towards areas of perceptually 'normal' exposure from regions of underexposed dark and overexposed bright. Therefore:

• higher contrast directs the eye; whereas
• lower contrast lends the eye greater freedom to roam over the entire surface.

A photographic phenomenon which directs the eye is vignetting - wide-angle lenses can concentrate more light in the centre of the image field than the periphery i.e. exposure increases radially inward. Thus a vignette draws attention towards the centre of the frame.

Exposure affects the perception of form
High contrast conditions break up the visual continuity of form, whereas low contrast conditions preserve it. Take, for example, two horizontal elements: one above and at an angle to the other, illuminated from above. High contrast will mean that the continuous form of the lower element will be visually broken by dark shadow cast by the upper element. Low contrast would allow the lower element still to be seen as intact with the casting of a lighter shadow.

Exposure affects colour saturation
Over-exposure leads to desaturated (muted, bleached, washed-out) colours. The practice of exposing to keep the highlights within the range of the film - the dominant procedure still today - came about with the introduction of Kodak's Kodachrome film in 1935. Kodachrome was intolerant of overexposure, but rewarded underexposure with rich saturated colours. 'Exposing for the highlights' is still relevant in the world of digital photography because overexposure results in unattractive digital clipping. In this respect, digital sensors share similar limitations to Kodachrome (discontinued in 2009).

Graphical features of exposure

• Silhouettes are the result from complete underexposure of the foreground, denying any foreground detail so that the outline of the dark shape tells the story.
• Flares also deny detail, but are achieved through overexposure, and are commonly used to unify or increase the activity of a composition.

The Rape of Polyxena, Loggia dei Lanzi, Florence

Photograph Copyright ©2013 Loo Yen Yeo. All Rights Reserved.

Concept: Dynamic tension (single object); Content (weak)

Description: 'The Rape of Polyxena' (1865) by Pio Fedi is a stunning sculptural group with a dynamic diagonal arrangement. It does not privilege a specific viewpoint. The sculpture alone is a masterpiece of dynamic tension, and it would have conveyed this on its own against a plain dark background.

So the philosophical question is, "is the image itself an example of dynamic tension, or is it simply a straight-ahead image of a subject possessing dynamic tension?" After all, if we imagine 'The Rape of Polyxena' on its own, we can see a complex of actual (body-line) and implied (eyeline) diagonals, and a single continuous spiral comprised of the two struggling female bodies - Queen Hecuba (below) and her daughter Polyxena of Troy - wrapped around the core of Neoptolomos, son of Achilles, standing over the slain prince Polites.

To answer that we'd have to look at the relationship of the subject with its environment. The regular pattern of the Uffizi's façade, positioned behind the sculpture on the right, provides a frame for Polyxena's outline to pull against. The brightly-illuminated arch over Via della Ninna on the left emphasises the desperate curve of Hecuba. From this angle, the strong directional chiaroscuro lighting emphasises the diagonals of form; and the intersection of the bottom frame with Polites' torso implies a continuation of that diagonal to infinity.

Title: Polyxena mine

02.04 Dynamic tension

Rather than thinking of images in terms of static balance, dynamic balance or imbalance, a different conceptual approach can be used to arrange elements in a way which energises the eye and leads it from the centre of the frame outwards.

Dynamic tension makes use of the energy inherent in structures; and compositionally locates them in positions where their energies pull or vector away from each other, most potently in highly contrasting directions. The achievement of dynamic tension is straightforward - the challenge, however, is to use it in a manner which does comes across as natural and with enduring appeal.

Images based on dynamic tension commonly incorporate a variety of contrasting diagonals; counter-lines, curving or straight; and vectors, real or implied. Overarching self-stabilising or enclosing structures, such as ellipses, are generally avoided as they resolve tension within the image.

Apse of Chiesa di Ognissanti, Florence, Italy

Photograph Copyright ©2013 Loo Yen Yeo. All Rights Reserved.

Concept: Vectors (diagonals)

Description: A simple example of a diagonal vector used to balance an image. Taken with a wide-angle lens, the three gold-red-gold lines of the carpet emerge from the bottom-right corner of the frame to converge at the chancel, drawing attention to the steps and lower front of the altar. The positional vector of the carpet serves to counterweight the lectern in the lower-left corner, without which the image would be unbalanced.

Title: Optical Trinity

03.11 Vectors

The eye likes to follow a line, or even the hint of one.

Visual composition makes use of this by directing the viewer's gaze from an obvious point of interest to a less obvious one, through the use of a joining line (or lines) possessed of movement and momentum. These connecting linear graphical elements - they must have a strong sense of direction and movement - are called vectors.

Vectoring is achieved compositionally through:

• Diagonals
  These are the most energetic of straight lines. It there are many of them, and if they converge, then the vector is stronger.
• Curves
  These lines have flow, pace, and even acceleration if they have a decreasing radius.
• Implied lines
  As created by the Gestalt joining of dots, edges of forms or shadows. These vectors are weaker, but may be the only possible alternative when real lines are unavailable.
• Representations of movement
  A viewer's eye 'reads ahead' of an object in motion. Hence an image of: a person walking, a swooping falcon, a speeding car, or a falling apple, drives the gaze along the same direction.
• Orientation
  Objects recognisably associated with movement: trains, cars, horses, and arrows can vector just by the direction they face.
   

(note: visual vectors, in this case, differ from the strict definition of vectors in physics which must have both magnitude and direction - curves are not vectors because of changing direction.)