Objective

“That which is considered to exist or be true independent of individual perception, interpretation, or internal states. In contrast to subjective experience, which is shaped by a perceiver’s prior knowledge, context, and cognitive biases, objective descriptions aim to refer to properties or measurements that are invariant across observers and verifiable through shared standards or external measurement.

In visual perception, particularly within empirical models like those of Palmer and Purves, the term objective often arises in contrast with constructed perceptual experience. For example, an objective shape can be defined as the spatial configuration of an object that remains unchanged across similarity transformations such as translation, rotation, dilation, and reflection​. This use provides a formal, mathematical grounding for assessing perceptual judgments—i.e., whether they align with a stable, external geometry.

However, under contemporary models of vision, including that of Purves et al., the notion of objective reality is treated with skepticism in perceptual terms. These models propose that what we perceive is not a direct representation of objective physical properties, but an empirical approximation based on the statistical outcomes of prior interactions. As such, the visual system does not aim to produce objective truth, but rather to guide successful behavior based on probabilistic inference. This casts doubt on the idea that perception can or should be evaluated against an ‘objective reality’ in any strict sense.

In artistic training and critique, the term objective may be used in several ways: as a standardized benchmark (e.g., objective shape matching, or objective measurement of value ranges), as a pedagogical checkpoint (e.g., identifying when a visual target is met independent of personal preference), or as a foil to subjective interpretation, especially in discussions of veridicality, perceptual distortion, or percept surrogate construction.

The Waichulis Curriculum emphasizes that while objective measurements (e.g., photographic reference values or proportional divisions) can be instrumental for calibration and training, all visual experiences and outputs are ultimately mediated by the perceptual system. Thus, the pursuit is not of objectivity per se, but of consistency, predictability, and communicative efficacy within a shared perceptual space.

In sum, objective refers to that which is meant to stand apart from individual variability—but in the domains of perception and art, it is better understood as a useful construct or training anchor, rather than an attainable or absolute condition.”

Objectivity in Art

“Claims that ‘there are no rules in art‘ or that ‘art is purely subjective‘ are common in popular discourse, but both assertions collapse under minimal scrutiny. While artistic activity certainly emerges from subjective agents, it is entirely possible—and often essential—to introduce and assess objective constraints, conditions, and outcomes within specific artistic contexts. To clarify this point, it is useful to draw from philosopher John Searle’s distinction between two types of rules:

Regulative rules guide behavior within an existing activity (e.g., ‘Use contrast to create focus’) and constitutive rules define what an activity is (e.g., ‘To be oil painting, you must use oil paint’).

Many so-called ‘rules of art‘ are not rules in this strong sense—they are heuristics (rules of thumb) or preferences (e.g., ‘Never center your subject’, ‘Use warm colors to advance‘). These may be useful in specific contexts but are not universally necessary or empirically grounded.

A true principle, by contrast, is a descriptive constraint grounded in empirical reality—drawn from the behavior of perception, matter, or cognition. Principles are not invented or agreed upon; they are observed truths that hold regardless of aesthetic, cultural, or procedural frameworks. For example: Marks must exceed a minimum threshold of contrast or spatial resolution to be perceptible. This is not a rule—it is a principle. It holds across all media and systems because it describes how vision works.

Constitutive rules may sometimes reflect or depend on principles (e.g., To engage in oil painting, one must use oil-based media), but their status as rules stems from their function in defining or organizing an activity—not from empirical necessity. They are contextual classifiers, not truths about perception. This distinction is essential: principles are necessary; rules are conditional.

A helpful analogy is the game of chess. Chess is an activity defined and governed by rules that were invented arbitrarily by subjective agents. However, once those rules are understood and agreed upon by the players—along with the shared goal of winning—each move, though carried out by a subjective agent, can be assessed as objectively better or worse within the context of the game. The subjective foundation of the rules does not diminish their functional objectivity in practice. In fact, if some rules are altered too drastically (e.g., allowing the bishop to move like a rook), it may no longer be chess at all.

Similarly, visual art may originate from subjective intentions, but once an artist adopts certain medium constraints, perceptual goals, or stylistic systems, objective evaluation becomes possible within those frameworks. That objectivity is contextual—not universal—but it is real and operative.

In the Waichulis Curriculum, we emphasize that objectivity in art is not about universal judgment or aesthetic absolutism—it’s about recognizing and working within definable, testable structures. The ability to make and assess visual decisions with reference to empirical constraints (e.g., optical legibility, material properties, perceptual thresholds) enhances creative fluency by focusing attention on what actually impacts the visual experience.

Finally, distinguishing between principles, rules, heuristics, and preferences is not creatively limiting—it is liberating. It allows artists to shed inherited dogma and make intentional, adaptive decisions grounded in what is necessary, what is useful, and what is merely optional. As with B.F. Skinner’s famous pigeons—who developed ritual behaviors based on false feedback—confusing superstition for structure only obscures the path to expert-level performance.”

Oblique

“In visual perception and pictorial composition, oblique refers to an orientation that deviates from both vertical and horizontal axes—typically at angles such as 45°, 30°, or 60°. In contrast to the primary orientations, oblique lines and shapes introduce visual tension, directional dynamism, and a perceptual departure from gravitational stability or architectural equilibrium.

From a vision science perspective, the oblique orientation is subject to a well-documented perceptual asymmetry known as the Oblique Effect—a phenomenon in which humans demonstrate reduced sensitivity and precision when processing oblique lines compared to vertical or horizontal ones. This asymmetry, first documented in psychophysical studies and later confirmed through neurological research, is believed to result from the overrepresentation of cardinal orientations in the visual cortex (V1), reflecting the dominance of vertical and horizontal contours in natural and built environments​.

In aesthetic contexts, the oblique orientation often connotes instability, movement, or unrest. As discussed in A Primer on Pictorial Composition, empirical studies have shown that viewers tend to rate vertically or horizontally aligned compositions as more balanced or pleasing compared to those dominated by oblique axes. This bias is echoed in experimental research on Mondrian paintings, where rotated versions containing primarily oblique elements were consistently judged less favorably​.

In compositional strategy, oblique elements are frequently used to evoke directional forces, leading lines, or a sense of narrative motion. When used deliberately, they can create asymmetry, visual propulsion, or spatial instability—powerful tools in visual storytelling or affect modulation. However, when employed indiscriminately, they may introduce perceptual ambiguity or undermine compositional clarity.

In the Waichulis Curriculum, the oblique orientation is explored both as a perceptual challenge and a design opportunity. Its reduced perceptual fluency demands increased sensitivity in edge control and alignment when integrated into illusionistic imagery. In exercises involving structural scaffolding or pictorial dynamics, oblique angles are treated as influential compositional agents—capable of disrupting or enhancing visual flow depending on their contextual deployment.”

Oblique Effect

“A well-documented perceptual bias in which humans exhibit reduced sensitivity, discrimination accuracy, and visual efficiency when processing oblique (diagonal) orientations compared to cardinal (horizontal and vertical) orientations. This asymmetry has been extensively studied in psychophysics, neurophysiology, and aesthetic evaluation, and is understood to have both neurobiological and experience-based components.

Neurologically, the visual cortex (V1) contains a disproportionately higher number of neurons tuned to cardinal orientations—a structural bias that may reflect the predominance of vertical and horizontal contours in both natural environments and man-made structures. This cortical overrepresentation results in increased perceptual fluency for cardinal orientations, enhancing detection thresholds, orientation memory, and line discrimination performance​.

From an empirical vision theory standpoint, the Oblique Effect is further explained by Dale Purves’ ranking theory of perception, which posits that percepts are shaped not by direct recovery of objective properties, but by the frequency of successful visual behaviors in response to similar stimuli over evolutionary time. In this model, orientations that occur more frequently in a species’ visual experience (e.g., vertical trees, horizontal horizons) yield more stable and efficient perceptual mappings. Less frequently encountered orientations, like 45° diagonals, are empirically ‘rarer’, resulting in weaker perceptual associations and thus less reliable visual output.

In aesthetic contexts, the Oblique Effect influences viewer response to compositional orientation. Studies on Mondrian paintings, for example, found that viewers preferred compositions aligned with vertical and horizontal axes over rotated versions containing oblique elements—a phenomenon termed the ‘aesthetic oblique effect’.

Within the Waichulis Curriculum, awareness of the Oblique Effect is crucial when addressing orientation accuracy in drawing tasks (especially rotational scaffolds and perspective challenges), and in compositional design where oblique axes are used to generate tension, instability, or narrative motion. Recognizing the perceptual demands of oblique structures allows artists to more effectively anticipate viewer response and control edge behavior in both drawing and painting media.”

Observation

“The active process of attending to, acquiring, and interpreting sensory information—most often visual—in order to extract relevant features, relationships, or structures from a given environment or stimulus. In both perceptual psychology and artistic training, observation is not passive seeing but a goal-directed, selective, and interpretive act.

In the Waichulis Curriculum, observation is a trainable skill central to all representational tasks. Artists are guided to distinguish between the idea of ‘raw visual input’ and intentional perceptual parsing, learning to identify structural relationships, spatial hierarchies, tonal dynamics, and material cues with increasing fidelity and control. Effective observation supports the construction of accurate percept surrogates—visual representations that communicate the perceptual consequences of light, form, and space.

Empirical models of perception (e.g., Palmer, Purves) emphasize that observation is mediated by prior experience, contextual expectations, and unconscious inference. Thus, what we ‘observe’ is not a direct imprint of the external world, but a probabilistic interpretation shaped by history and heuristic assumptions.

In the domain of expertise research, observation also plays a methodological role. Studies such as those documented in the Cambridge Handbook of Expertise and Expert Performance employ both systematic observation (i.e., structured data collection using predefined criteria to record specific behaviors or features in a controlled or repeatable way) and participant observation (i.e., a qualitative method in which the observer is actively engaged in the environment or activity being studied, often blending observation with immersion) to analyze behavior in naturalistic settings. These methods aim to understand how experts organize, refine, and execute complex practices across time, often capturing micro-level decisions, effort allocation, and environmental interactions​.

Importantly, observation is not limited to visual data alone—it can encompass behavioral, contextual, and spatial variables, especially in fields like visual anthropology, instructional design, and cognitive task analysis​.

In short, observation is both a perceptual process and a methodological tool. In the visual arts, it underpins the fidelity and intentionality of image-making. In the sciences of skill acquisition, it enables the rigorous study of performance. In both contexts, observation is defined not by passive exposure, but by active, structured engagement with visual and contextual information.”

Observational Representationalism

“Representational image-making based on direct observation of a subject. This practice emphasizes perceptual accuracy and often involves iterative refinement through visual comparison, measurement, and correction. Unlike schematic or symbol-based depictions, observational representationalism seeks to align the perception of the surrogate image (A2) with the viewer’s perceptual expectations of the referent (A), in alignment with the Waichulis A1 model of perceptual mediation.”

Obtuse Angle

“Any angle greater than 90 degrees but less than 180 degrees. In Euclidean geometry, this means the two rays or line segments forming the angle diverge more widely than those of a right angle. Obtuse angles are often contrasted with acute angles (measuring less than 90°) and right angles (measuring exactly 90°).

In visual perception, however, the experience of obtuse angles can deviate from geometric expectation due to the projective ambiguity of the retinal image. As detailed by Purves et al., the angle we perceive is influenced not by the actual angular subtense of a physical object (i.e., the angle formed at the eye by the lines extending to the endpoints of a viewed object—often determining how large it appears visually), but by the empirical frequency of angular configurations encountered over time. Specifically, obtuse angles are typically perceived as slightly smaller than they really are, while acute angles are often seen as larger​.

This perceptual bias arises from the statistical nature of visual experience. According to projective geometry and empirical modeling, a projected obtuse angle on the retina is most often caused by real-world angles that are somewhat smaller than the projection itself. Conversely, acute projections tend to originate from source angles that are larger than the image implies.

This mismatch underscores the empirical strategy of vision: the brain does not aim for a geometrically accurate reconstruction, but instead produces percepts based on the most likely real-world sources of a given stimulus, derived from the accumulated history of successful interactions with the environment.

In art and design, understanding this perceptual shift is critical when constructing spatial illusions, architectural perspective, or compositions involving angular tension. Artists can manipulate or compensate for these tendencies to control visual emphasis or imply depth.

Thus, the obtuse angle is not only a mathematical measurement—it is a perceptual event shaped by geometry, visual history, and contextual inference.”

Occlusion (Depth Cue)

“A fundamental depth perception mechanism in which an object partially obscures another, establishing a spatial hierarchy within the visual field. Since the brain interprets occluded objects as being farther away, occlusion provides a powerful monocular depth cue that does not require binocular disparity. Effective use of occlusion enhances realism in two-dimensional compositions by reinforcing the layering of elements and establishing a sense of atmospheric perspective. The strategic placement of occluding forms can also create tension, direct attention, or suggest movement, making it a key tool in both representational and abstract art.”

Occlusion Geometry

“The spatial relationships and structural logic governing how one object blocks, obscures, or partially reveals another in a visual field. It is a critical feature of visual perception and image construction, as it provides essential cues about depth, spatial ordering, and three-dimensional form from two-dimensional input.

In perceptual science, occlusion is one of the most reliable and early-developing cues for depth—arising from the regularity that closer objects interpose themselves between the viewer and farther surfaces. The brain uses occlusion relationships (e.g., T-junctions, contour interruptions, and edge terminations) to infer relative spatial positioning even when absolute distances are unavailable​.

The term geometry in this context points to the structural consistency of such occlusion events. For example, a visible T-junction where one contour terminates abruptly against another usually implies that the terminating edge belongs to an occluded surface, and the uninterrupted edge belongs to a closer object. This inference holds across varied scenes, supporting its geometric regularity.

In pictorial composition and representational drawing, occlusion geometry guides the construction of believable spatial layering. Mastery of occlusion geometry allows an artist to: clarify foreground-background relationships, convey depth without relying solely on linear perspective, and resolve visual ambiguities in complex overlaps or interpenetrating forms.

Incorrect occlusion geometry—such as reversed overlaps or ambiguous edge junctions—can undermine depth cues and flatten the visual field, resulting in spatial contradictions.

While occlusion may seem a straightforward cue, its interpretation is deeply intertwined with projective geometry, assumptions of surface continuity, and object completeness. Many perceptual models, including Marr’s 2.5D sketch and Palmer’s surface-based representations, treat occlusion as a foundational organizational constraint in the transformation from retinal image to three-dimensional percept​.

Thus, occlusion geometry describes both the rules governing physical interposition and the visual system’s strategies for decoding those rules to construct coherent spatial interpretations from incomplete input.”

Old Masters

“The term Old Masters refers generally to the highly skilled European painters—primarily of the Renaissance, Baroque, and early modern periods—who are retrospectively recognized for their technical mastery, enduring influence, and canonical contributions to the development of Western art. The designation typically includes artists such as Leonardo da Vinci, Michelangelo, Raphael, Titian, Rembrandt, Rubens, Velázquez, Vermeer, and others active from approximately the 14th to the 18th century.

The label is not contemporaneous; no artist referred to himself as an ‘Old Master.’ Rather, it is a retrospective construct, popularized in the 18th and 19th centuries, particularly through art collection, connoisseurship, and early art-historical writing. By the early 20th century, the term had become widely institutionalized, appearing in museum literature, auction catalogs, and studio materials (e.g., ‘Old Masters mediums’).

While there is no strict definition, ‘Old Master’ typically implies European origin, pre-19th-century activity, and recognition for a high degree of technical skill, compositional intelligence, and innovation within the visual arts.

The phrase carries with it a degree of mystique—often invoking notions of lost knowledge or ‘secret techniques’. This sentiment was especially widespread during the 18th and 19th centuries, when the decline of workshop-based training and the rise of industrial art materials led to efforts to reverse-engineer the methods of past painters. These often speculative reconstructions contributed to the romantic notion of ‘the secrets of the Old Masters’—a phrase that, while evocative, is largely discredited by modern research. Ralph Mayer, Charles Eastlake, and A. P. Laurie all emphasized that what was once seen as lost knowledge was often simply sound craftsmanship, preserved through guild tradition and studio practice​.

As Mayer noted, the idea of ‘secret formulas’ likely emerged from a misunderstanding of medieval and Renaissance treatises, where the word ‘secret’ often meant technical knowledge not publicly taught, but not necessarily esoteric or hidden. In reality, much of the mastery attributed to these painters was based on deliberate, empirically grounded studio systems involving: layered construction of paint films, the controlled use of oil-resin mediums, and a deep integration of drawing, design, and optical observation.

In contemporary usage, the term is sometimes appropriated as a marketing or pedagogical tool (e.g., ‘Old Masters technique’), which may or may not reflect accurate historical methods. Caution is therefore advised in uncritically accepting claims of fidelity to such methods without technical substantiation.

In summary, Old Masters is both a cultural category and a symbol. While it denotes historical figures of remarkable technical achievement, it also reflects changing attitudes toward skill, tradition, and the idealization of past craft.”

Oil Ground

“A type of priming layer composed primarily of oil (usually linseed oil) and white pigment, typically lead white or titanium dioxide, applied to a support such as canvas or panel to prepare it for oil painting. Unlike traditional gesso grounds—which are absorbent and water-based—oil grounds create a less absorbent, more flexible surface better suited to the handling characteristics of oil paint.

Oil grounds are prized for producing a durable, luminous, and responsive surface that allows oil paints to retain their richness, saturation, and working time. When properly prepared, they provide sufficient ‘tooth’ for adhesion while minimizing the over-absorption of the oil binder—a problem that can lead to issues like sinking, poor film formation, and embrittlement over time.

Historically, oil grounds have often included white lead in oil, especially in the preparation of grounds for durable, professional-grade paintings. These materials, typically sold in cans or pails rather than artist-grade tubes, were ground to a soft paste and may include a small amount of mineral spirits or turpentine to improve spreadability​. Because of toxicity concerns, modern oil grounds may substitute titanium white or zinc white, though these alternatives lack some of the working properties of lead-based formulations.

A well-prepared oil ground typically requires: proper sizing of the support to prevent oil penetration (e.g., with gelatin or PVA), thorough drying between layers to avoid cracking or delamination, and sufficient drying time and hardness before painting begins, as undercured grounds can destabilize upper layers.

In contrast to acrylic gesso grounds (which dry rapidly and are water-based), oil grounds may take several days to weeks to cure fully. However, their long-term chemical compatibility with oil paint makes them a preferred option for conservation-grade work and traditional oil techniques.

Thus, an oil ground serves not only as a preparatory layer but as a critical component of the painting’s structural and optical behavior, supporting both mechanical stability and aesthetic performance.”

Oil Paint / Oil Painting

Oil paint is a slow-drying, film-forming painting medium consisting of finely ground pigment particles suspended in a drying oil, most commonly linseed oil, though other oils such as walnut, poppy, and safflower are also used. When exposed to air, these oils undergo a process of oxidation, polymerization, and cross-linking, eventually forming a durable and flexible solid film. This chemical curing process distinguishes oil from faster-drying media like acrylics or watercolor, and has significant implications for working time, film integrity, and long-term conservation.

Oil painting refers to the practice of using this medium in artistic expression. The technique is known for its capacity to support a wide range of visual outcomes—from transparent glazes to dense impastos, from subtle value transitions to high-chroma optical effects. Its long open time allows for extensive blending, edge modulation, and gradual refinement, making it particularly suited to perceptual and representational work.

Historically, oil painting was adopted in European practice during the 15th century, with notable expansion through the work of Flemish and Italian painters. Its dominance continues today due to its visual potential, flexibility, and material stability—although these strengths also come with challenges, including slow drying, susceptibility to yellowing, and the need for careful layer management (e.g., fat-over-lean principles to prevent cracking).

Within the Waichulis Curriculum, oil paint serves as the core medium of the Language of Painting (LOP) program. Students are trained to understand many aspects of oil paint including (but not limited to): the distinction between direct (alla prima) and indirect (layered) techniques, the role of mediums in modifying behavior (e.g., viscosity, gloss, drying rate), the mechanics of edge control, value transitions, and surface modulation, the chemical and procedural causes of issues such as sinking (loss of saturation in dark passages due to oil absorption into underlayers).

Special emphasis is placed on safe studio practices, including the avoidance of solvent-based materials, the use of slow-drying extenders or modifiers when appropriate, and the proper handling and disposal of oil-soaked materials (due to fire risk from spontaneous combustion).

Oil paint, within this curriculum, is not only a medium for visual effect—it is a system of perceptual structuring, requiring an understanding of material behavior, procedural sequencing, and sensory calibration.”

Oiling Out

“The process of applying a thin, uniform layer of drying oil or medium to a dry or sunken area of an oil painting to restore color saturation, value depth, and surface uniformity. The practice is primarily used to counteract sinking—a condition where a paint layer appears matte, chalky, or patchy due to the absorption of its binding oil into an underlayer or ground, leaving pigment visually underbound.

A helpful analogy is that of a seasonal arroyo: after rainfall, a creek bed appears dark and rich, but as the moisture is absorbed into dry soil, the surface lightens and dulls. Similarly, sunken paint may initially appear vibrant, only to fade unevenly as oil is absorbed. Oiling out temporarily restores that visual richness, allowing for accurate judgments and further painting​.

The functions of oiling out include: Visual Restoration: It replenishes oil at the surface, restoring gloss and chromatic depth, especially in dark values prone to rapid drying or underbinding. Surface Unification: It helps even out inconsistencies in surface sheen that might mislead value or hue judgments during the painting process. Creates a Couch: It introduces a thin oil layer onto which new paint can be applied more smoothly—a ‘wet couch‘ that improves brush glide and blending, and reduces drag on dry areas​.

Additional considerations for oiling out include: Increased Yellowing Risk: Applying unpigmented oil may increase the likelihood of yellowing over time, particularly if the oil used (e.g., linseed) is prone to oxidative discoloration. This risk is supported by conservation findings and sources like Mayer’s Artist’s Handbook​. Interference with Dry Media Dynamics: The use of a couch may reduce the tactile feedback and resistance valued in certain application strategies (e.g., Analog Brush Load Strategy), and may alter opacity control. Conservative Application Required: Excess oil can weaken paint film integrity or delay drying. Instructional guidance stresses applying only the minimum necessary to restore the appearance without overloading the surface​.

In practice, oiling out should be undertaken only when the underlying paint is fully dry to the touch, and the surface is free from curing disruptions. While effective for in-progress corrections and aesthetic unity, its use should be measured and context-sensitive, always considering the long-term stability and optical behavior of the paint film.”

Opacity

“The optical property of a material that prevents light from passing through it, resulting in a fully obstructed view of objects behind it. Unlike transparency, which allows light to pass through unobstructed, or translucency, which permits partial light diffusion, opaque materials completely block light transmission, reflecting or absorbing incoming light instead. Common examples of opaque materials include wood, metal, stone, and thick paint layers, where visibility through the material is entirely obstructed.

In visual perception and rendering, opacity plays a crucial role in defining solid forms, controlling depth relationships, and influencing light interaction within a scene. In painting and digital media, opacity is often adjusted to control layering effects, glazing techniques, and the buildup of color density, allowing artists to manipulate surface depth and material qualities. Understanding opacity in relation to transparency and translucency is essential for accurately depicting a wide range of materials and achieving realistic or stylized visual effects.”

Opalescent Color

“A somewhat cloudy, semi-translucent visual effect characterized by scattered internal light and subtle spectral shifts, similar to what is observed in natural opal gemstones. Unlike interference or pearlescent effects, which rely primarily on surface-layer reflection and structural interference, opalescence involves subsurface light scattering through multiple layers of microscopic inclusions or spheres suspended within a translucent medium. As light enters the material, it is diffused, scattered, and partially refracted—producing a glowing effect that often shows soft, cool bluish tones in reflected light and warmer, reddish tones in transmitted light (a phenomenon related to Rayleigh scattering).

The term comes from the appearance of precious opal, where hydrated silica spheres arranged in near-regular patterns cause diffraction and scattering that yield both milky diffusion and flashes of spectral color. In manufactured materials, opalescence is often simulated in glass, ceramics, glazes, and some plastics—and occasionally in specialty paints or coatings. Unlike interference colors, which are angle-sensitive and metallic in nature, opalescent effects are typically soft, cloudy, and light-dependent, producing a gentle luminosity rather than sharply defined chromatic shifts.

Common uses of opalescent finishes include art glass (e.g., Tiffany lamps), opalized jewelry, glazed pottery, dental ceramics, and occasionally decorative surface treatments in architecture or packaging. In fine art, opalescence is rarely pursued directly through paint but can be suggested through layering translucent glazes with suspended particulate matter or through mixed-media applications.

As with pearlescent effects, opalescent surfaces can be affected by surface dulling, binder yellowing, or improper light conditions, all of which can obscure the desired depth and glow. Additionally, in manufactured materials, particle size and distribution must be carefully controlled to avoid unevenness or unwanted opacity.

In summary, opalescent color is defined by cloudy translucency with internal spectral scattering, producing a glowing, clouded appearance rather than sharp color shifts. It is distinct from pearlescent (which is more reflective and surface-based) and iridescent/interference effects (which are structurally reflective and angle-sensitive), offering a uniquely ‘ethereal’ visual quality associated with diffusion and internal light play.”

Open Composition (Pictorial)

“A pictorial arrangement in which visual elements appear to extend beyond the boundaries of the image, suggesting a continuation of space, movement, or narrative outside the frame. Unlike closed compositions—which are self-contained and inwardly focused—open compositions are characterized by partial forms, directional cues, and spatial openness that imply connection to a broader environment.

This type of composition often includes figures or objects cropped at the edges of the image. It can utilize diagonals, directional movement, or gaze lines in an attempt to lead the viewer out of the frame. It can also emphasize asymmetry, dynamic imbalance, or fragmentation, often creating a more spontaneous or naturalistic feel.

In perceptual terms, open compositions engage the viewer’s sense of continuity with the surrounding world. Rather than resolving visual attention within a contained structure, open compositions encourage exploration, inference, and contextual imagination.

Historically, open compositions are prominent in genres like landscape, genre painting, and narrative scenes, especially in the Baroque and modern eras, where movement and momentariness were emphasized. Within the Waichulis framework, open composition is recognized as a strategy that leverages ecological expectations and peripheral stimulation, often enhancing realism by mimicking how we experience incomplete, ambient information in natural vision​.

In sum, an open composition invites the viewer to participate in a world that exists beyond the edges of the image, contrasting the enclosed, self-referential nature of a closed composition.”

Opponent Process Theory

“A model of human color vision proposing that perception is governed by three opposing neural channels: red-green, blue-yellow, and black-white. This theory, developed by Ewald Hering in the 19th century and later confirmed through modern neurophysiology, explains how antagonistic interactions between photoreceptor signals contribute to color perception. The presence of one color in a pair inhibits the perception of its opponent (e.g., strong red input suppresses green perception). This mechanism contributes significantly to phenomena such as afterimages, simultaneous contrast effects, and color constancy, playing a crucial role in both artistic color theory and practical applications like digital color correction.”

Optic Flow

“The dynamic pattern of apparent motion across the visual field that occurs as an observer moves through an environment. It was first formally articulated by James J. Gibson as part of his ecological approach to visual perception, wherein the structure of the retinal image during movement provides reliable cues for spatial orientation, navigation, and self-motion​.

The basic structure of optic flow depends on the observer’s direction and speed of motion relative to environmental surfaces. For example: as you walk toward a fixation point, the visual scene appears to expand radially from that point (optic expansion), if you move away, a pattern of optic contraction occurs. Lateral movement creates flow patterns where objects shift in opposite directions based on their depth.

These motion gradients vary with depth: the farther an object is from the fixation point, the more rapidly it appears to move across the retina. This provides a reliable cue to relative depth, even from monocular input​.

Importantly, optic flow also allows for the perception of self-motion, including both direction and speed. The focus of expansion in the optic flow field indicates where the observer is heading. This capacity underlies behaviors like balance maintenance, path correction, and navigation in complex environments​.

In artistic contexts, cues drawn from optic flow can be strategically deployed to imply motion, guide visual attention, or simulate environmental immersion. For instance, directional textures, radiating forms, or implied velocity fields can mimic real-world optic flow to anchor the viewer’s gaze, reinforce compositional thrust, or simulate depth via motion-parallax analogues. These cues are often seen in dynamic compositions that seek to induce perceptual momentum or tension. Artists exploiting such dynamics are not imitating physical motion per se, but recruiting the brain’s sensitivity to expected motion patterns—an empirical shortcut to perceived movement, orientation, and immersion.

Thus, optic flow is both a natural perceptual mechanism and a pictorial tool. In both realms, it organizes the visual field through structured change, enabling the perception of spatial layout, self-movement, and attentional focus in a visually dynamic world.”

Optical Mixing

“A perceptual phenomenon in which distinct colors/colorants remain physically separate, but their spatial arrangement and viewing distance cause the brain to interpret them as a new color. Unlike physical (subtractive) mixing, where pigments combine and alter the wavelengths of light being reflected, optical mixing preserves the original chroma of each color, often resulting in more vibrant and luminous effects. This perceptual blending occurs due to the way the brain integrates small, closely spaced areas of color into a unified experience rather than perceiving each one individually. It is a key principle in pointillism, halftone printing, textile design, and digital imaging.”

Optics

“The branch of physics concerned with the behavior and properties of light, including its interactions with matter and the instruments used to manipulate it. In the context of visual perception and image-making, optics plays a critical role in explaining how light behaves as it travels through space, reflects off surfaces, refracts through transparent media, and ultimately forms images on retinal, sensor, or substrate surfaces.

Optics is traditionally divided into several subfields: Geometrical optics, which models light as rays and focuses on principles like reflection, refraction, and lens behavior; Physical optics, which deals with the wave nature of light, including interference, diffraction, and polarization; Physiological optics, which studies how the eye and brain respond to optical stimuli—a major focus of vision science; Ecological optics, as developed by James J. Gibson, which emphasizes the structure of optical information in the environment (the ambient optic array) and its role in perception without requiring internal reconstruction​.

In visual art, understanding optics is essential for the realistic rendering of form, light, and space. Knowledge of optical behavior informs techniques such as: simulating the effects of specular vs. diffuse reflection, rendering refractive distortion in glass or water, and creating depth cues through linear perspective and atmospheric attenuation.

From a perceptual standpoint, optics provides the initial conditions for visual experience. The retinal image—the 2D optical projection of a 3D scene—is not a faithful record of the external world, but rather a collapsed and ambiguous signal. The brain must resolve this ambiguity through inferential processes based on prior exposure to the structure of optical stimuli (see inverse problem and empirical vision).

The Waichulis Curriculum incorporates principles of optics not merely for technical accuracy but to cultivate an intentional awareness of light behavior as it relates to perception and pictorial construction. This includes exercises that explore light-matter interactions, cast shadow logic, and the perceptual consequences of varied illumination geometries.

In sum, optics is not only the physical foundation for image formation—it is the interface between the world and the eye, and thus a key domain of knowledge for any visually literate practitioner.”

Orbital Sander

“A power tool used to sand or smooth surfaces through a random orbital motion—a pattern that combines rotation with slight elliptical oscillation. This dual movement minimizes visible swirl marks and prevents repetitive abrasion patterns, making it particularly effective for even surface preparation on wood panels, hardboard, and gessoed substrates.

Orbital sanders are commonly used in art studio settings to: smooth rigid supports (e.g., hardboard or MDF) prior to priming, level gesso or oil grounds after priming is complete, or, for some, in between coats, or to create a uniform surface texture that promotes consistent media behavior and adhesion.

The tool uses round sanding pads that attach via hook-and-loop (Velcro-like) or adhesive backings and operate at variable speeds depending on the model. The random orbit pattern prevents the abrasive from following a fixed path, thereby reducing the risk of gouging or directional scoring.

It is important to distinguish an orbital sander from a rotary sander, which spins in a fixed circular motion and is more prone to leaving directional scratches. Orbital sanders are preferred when the goal is to maintain surface flatness while removing material in a controlled, contextually less-aggressive manner.

In curriculum-aligned practices, an orbital sander can be a critical part of support preparation protocols, ensuring that the working surface meets the standards of planarity, absorption control, and surface feel required for representational media applications.”

Organoleptic Property

A sensory attribute of a material substance that can be directly perceived by one or more of the sense organs—typically sight, touch, taste, smell, or hearing. These properties are intrinsic to the physical material and are evaluated through direct sensory engagement rather than instrumental measurement.

In visual art and conservation contexts, organoleptic properties refer specifically to observable and experiential qualities of materials—such as the color of a pigment, the glossiness of a varnish, the texture of a support, or the viscosity of a binder. These attributes influence both aesthetic decisions and material behavior in practice.

Some examples include: the color of a paint mixture as seen on a palette is an organoleptic property when evaluated as the appearance of a physical substance. The tactile texture of a ground surface (e.g., tooth or smoothness) is an organoleptic property relevant to how a medium responds under application. The smell of a solvent or sound of a medium (e.g., dry media moving across a surface) may also be considered under this category in certain contexts (e.g., conservation, material testing, or sensory design).

However, it is important to distinguish this material-based use from perceptual attributes like color, shape, or motion as experienced in pictorial space. For example, color in a painting is no longer an organoleptic property when considered as a depicted perceptual phenomenon governed by ambient light, chromatic adaptation, and contextual contrast. In that context, it becomes a component of visual coding, not a property of a substance.

Thus, while some properties (like color or texture) can appear in both material and perceptual domains, they only qualify as organoleptic when directly tied to the sensory characteristics of a physical substance.

Understanding this distinction is critical for disciplines such as conservation science, materials education, and studio practice, where differentiating between the material behavior of substances and their visual representations informs both evaluation and execution.”

Original

“A term used across visual art, design, and authorship domains to denote primacy (i.e., the condition of being first in origin, sequence, or importance relative to a set of alternatives) of creation, but which can carry varied and context-dependent meanings. In general, an original refers to either a work created firsthand by its author, the initial iteration of a work, or the unique artifact from which derivatives or reproductions are made. However, the functional meaning of original shifts depending on whether one is addressing authorship, material objecthood, conceptual development, or legal ownership. Common usages include:

Authorship/Creative Origin: In this context, ‘original’ refers to the work as originated by the artist, distinguishing it from copies, prints, or derivative works. This may apply regardless of medium (e.g., a digital file may be the original despite its replicability). The term emphasizes creative authorship, intentionality, and source-level generation, not necessarily uniqueness in a material sense.

Material Objecthood (i.e., the condition of existing as a tangible, bounded artifact with physical presence and spatial coherence): Within conservation and physical curation, an original refers to the primary physical artifact—the object first made by the artist’s hand, as opposed to a print, cast, or reproduction. This is particularly important in contexts where material authenticity (e.g., brushwork, pigment composition, substrate) is relevant to valuation, attribution, or preservation.

Precedent Within a Series: In iterative processes, such as studies, prototypes, or preliminary designs, ‘original’ may denote the first version or initiating design, which may later be modified, elaborated, or refined. Here, ‘original’ functions chronologically, not necessarily hierarchically.

Legal and Intellectual Property Contexts: In copyright and intellectual property law, originality refers to a work that is independently created and possesses a minimal degree of creativity, qualifying it for legal protection. This usage does not require novelty in a broader sense—it need not be unique in idea or execution—but must be authored and not copied.

Cultural or Conceptual Usage: In casual or critical discourse, ‘original’ may be used to describe something perceived as novel, unconventional, or highly individualized—though this meaning is interpretive and often subjective. In this usage, originality is sometimes equated with distinctiveness, though it may have no direct bearing on whether the work is derivative or not.

It is important to note that a work may be original in one sense but not in another. For example, an oil painting may be the original physical object (materially), but may incorporate compositional structures or visual motifs derived from preexisting works or cultural conventions—raising questions about its creative originality. Likewise, a digital artwork may be fully original in authorship but endlessly reproducible without degradation—complicating assumptions that ‘original’ implies ‘singular’.

In training environments like the Waichulis Curriculum, understanding this distinction is vital for: clarifying attribution (e.g., student-generated vs. master copies), establishing feedback criteria (e.g., when evaluating conceptual originality), or documenting process (e.g., original study vs. refined execution.)

In short, ‘original’ should always be interpreted relative to context, and educators and artists alike are encouraged to qualify the term—specifying whether it refers to creative authorship, material primacy, or conceptual innovation.”

Originality

“The perceived novelty, distinctiveness, or non-derivativeness of a work, process, or idea relative to existing precedents. Originality is not an inherent property of a work but a relational judgment, shaped by cultural context, viewer familiarity, and domain-specific expectations. It reflects the extent to which a visual, structural, or conceptual element is experienced as deviating meaningfully from the familiar, while still retaining a degree of coherence or intelligibility.

In perceptual and aesthetic terms, originality is often attributed when a work violates or reconfigures established compositional, symbolic, or procedural norms, introduces unexpected combinations or novel structures, or demonstrates unconventional approaches to familiar subject matter.

However, originality is distinct from mere complexity or difference. A highly unusual form that lacks structural coherence or communicative intent may be confusing or illegible, rather than original. Similarly, a work that is entirely derivative in form may still feel original through reinterpretation, contextual reframing, or novel execution.

In skill-building environments like the Waichulis Curriculum, originality is not treated as an isolated goal, but as a property that emerges when perceptual fluency, technical control, and intentional variation intersect meaningfully. A focus on originality too early in training can lead to premature stylization or symbolic overreach; however, as fluency develops, originality becomes a powerful vehicle for personal voice, visual problem-solving, and communicative distinctiveness.

In intellectual property law, originality refers more narrowly to a work that is independently generated and minimally creative, which qualifies it for copyright protection. This legal usage does not require artistic novelty—only that the work is not copied.

In summary, originality is best understood not as a static trait but as an emergent condition (i.e., a system-dependent state that arises through the interaction of multiple components, but remains context-sensitive, temporally contingent, or interpretive—unlike an emergent property, which stabilizes as a functional trait)—a perceptual and cultural response to structured deviation, grounded in intention, execution, and audience interpretation.”

Originality/Fluency Problem

“A cognitive and aesthetic conflict that arises when an artist’s pursuit of originality—defined as visual, conceptual, or procedural deviation from convention—interferes with the viewer’s ability to fluently process the work. The problem emerges from the empirically supported observation that many positive aesthetic responses are driven by fluency—the ease and efficiency with which information is perceived, organized, and interpreted. Characteristics such as clarity, coherence, symmetry, rhythm, and perceptual predictability often contribute to positive evaluations precisely because they reduce cognitive effort and increase processing speed.

In contrast, originality often requires the disruption of fluency by introducing unfamiliar elements, unexpected forms, or novel configurations. While such disruptions can lead to deeper engagement or reappraisal, they also risk inducing interpretive friction, ambiguity, or resistance, particularly when fluency thresholds are exceeded.

The Originality/Fluency Problem thus identifies a structural tension in artmaking: Fluency maximizes accessibility, comfort, and aesthetic ease. Originality aims to differentiate, challenge, or surprise, yet many of the perceptual and affective rewards associated with successful images—such as elegance, balance, or resonance—are rooted in perceptual fluency, not innovation per se.

This problem is especially relevant in training environments, where artists are encouraged to ‘develop a personal voice’ or ‘innovate,’ yet may prematurely prioritize stylistic deviation at the expense of clarity, structural coherence, or skillful modulation. It is also relevant in advanced critique, where originality is often overemphasized as a value, without accounting for its potential cost to readability or aesthetic pleasure.

While the tension between originality and fluency cannot be eliminated, it can be intentionally managed. Several strategies have proven effective in preserving perceptual legibility while supporting innovation:

Localized Innovation within Familiar Frameworks: Introduce novel or experimental features at the level of detail (e.g., texture, edge behavior, chromatic deviation), while maintaining broader structural fluency in subject, composition, or spatial hierarchy. (See: Novel-Familiarity Balance Heuristic.)

Schema Subversion with Redundant Support: Subvert common visual schemas (e.g., lighting conventions, spatial cues), but provide reinforcing cues elsewhere to ensure the work remains navigable and interpretable.

Delayed Fluency: Employ controlled ambiguity or complexity that initially adds strategic resistance to interpretation but resolves with continued engagement—rewarding the viewer with eventual fluency (common in layered narratives, symbolic structures, or spatial puzzles).

Strategic Familiar Anchors: Embed easily readable elements (e.g., faces, bodily gestures, or clear tonal hierarchies) within a composition that employs atypical visual organization or structural deviation. These elements provide perceptual entry points, support figure-ground assignment, and help stabilize attention within more novel or ambiguous regions.

Progressive Modulation: Gradually introduce deviation across compositional scale or sequence (e.g., from center to periphery or foreground to background), preserving early processing fluency while allowing for depth and novelty over time.

These strategies do not eliminate the conflict but harness its productive potential, allowing for works that are both distinctive and engaging, both challenging and coherent.”

Origin-Destination Line Exercise

“The Origin-Destination Line Exercise is the first core perceptual-motor task in the Waichulis Curriculum, designed to train deliberate, confident, and controlled mark-making. The exercise requires the artist to draw a single, fluid line connecting two predetermined points: an origin (start) and a destination (end). The goal is to produce a smooth, uninterrupted stroke that reflects both directional intent and pressure control, eliminating hesitation, segmented strokes, or ‘searching’ behaviors common to early-stage learners.

This exercise marks the beginning of the artist’s transition from low-confidence, detail-focused mark-making to global perceptual processing. Most notably, it is the curriculum’s first structured introduction to perceptual and cognitive chunking—the process by which discrete, low-level stimuli (such as short line segments) begin to be perceived and executed as unified wholes. Early learners often view long lines as sequences of disconnected movements, typically bounded by the limits of their perceptual attention or ‘cone of focus’. Through repetition and guided refinement, learners begin to process and execute larger structures more holistically, resulting in smoother lines and greater mark confidence​.

The Origin-Destination Line also introduces important physical dynamics of mark delivery, including grip experimentation, directional variability, and the use of a ‘gliding stroke’ (often described as the airplane dynamic—landing before and lifting after the stroke). This movement pattern is foundational to both drawing and painting workflows throughout the curriculum.

Additionally, the exercise incorporates the Diagnostic Wheel, a self-assessment strategy used to evaluate directional inconsistencies. This fosters early development of adaptive feedback and error correction—critical skills for managing line quality across all orientations.

In sum, the Origin-Destination Line Exercise is not merely an introduction to line—it is the learner’s first structured engagement with intentionality, motor planning, and perceptual chunking, forming the cognitive and physical foundation for increasingly complex visual tasks to follow.”

Ornament

“Visual or structural elements added primarily for aesthetic appeal, rather than for communicative or functional necessity. In the context of visual art and design, ornamentation may include decorative motifs, patterns, embellishments, or symbolic flourishes that enhance surface interest without altering the core function or structure of the object or image.

Historically, ornament has played shifting roles across artistic movements. In classical architecture and decorative arts, it signified status, craft, and cultural identity. In contrast, modernist schools like the Bauhaus rejected ornament for its own sake, advocating for functional clarity and ‘material honesty’ (i.e., the practice of allowing a material to visibly retain its natural properties or structural role rather than concealing, imitating, or altering its inherent character).

In the Primer on Pictorial Composition, ornament is conceptually defined within a quadrant model that considers aesthetic quality and communication efficacy as two axes. A visual product that possesses aesthetic attractiveness but does not communicate discernible content may be classified as ornament—distinguished from utility (informative but unattractive), art (both effective communication and aesthetic qualities), or trash (neither communicative nor aesthetic)​.

It is crucial to recognize that ornament is not a negative label. In many cases, it reflects cultural values, personal expression, or pattern generation (recognition) biases that appeal to human perception. However, when ornament is applied without regard to structural coherence, perceptual legibility, or intentional communication, it risks becoming superfluous visual noise.

Within the Waichulis Curriculum, the use of ornament is encouraged only when it serves defined visual or promotes a communicative purpose—as a device that enhances, rather than distracts from, the core perceptual goals of the image.”

Orthogonal

“In its most formal mathematical sense, orthogonal means perpendicular—that is, intersecting at a 90-degree angle. Two lines, planes, or vectors are orthogonal if the angle between them is exactly 90°, and in vector math, orthogonality can also imply independence (i.e., the dot product of two orthogonal vectors equals zero).

In visual art, particularly in linear perspective drawing, the term orthogonal is often used (though somewhat imprecisely) to describe lines that appear to recede into space and converge toward a vanishing point on the horizon line. For example, the parallel edges of a road or building may be labeled as ‘orthogonals’ in perspective diagrams, even though they are not orthogonal to anything within the depicted image plane. This use of the term comes from traditional perspective terminology and should be understood as a convention rather than a strict geometric description.

In technical or perceptual terms, an orthogonal projection is a method of depicting three-dimensional forms using lines that are perpendicular to the projection plane. In a coordinate system, the x, y, and z axes are mutually orthogonal, forming the foundational framework for Cartesian space.

In representational drawing and painting, understanding true orthogonality can help artists assess the relationships between edges and planes in three-dimensional form, accurately structure perspective grids, and distinguish between parallel, converging, and perpendicular relationships within a pictorial construction.

While orthogonal is often colloquially applied to ‘converging lines in perspective,’ the more precise usage refers to angular relationships that define form and spatial construction both within and outside of projection systems.”

Outline

“A consistently applied boundary line that encloses a shape without depicting depth, light interaction, or surface variation. Outlines define an element in a flat, two-dimensional manner, emphasizing shape. Unlike contour lines, which vary in weight, curvature, and detail to suggest three-dimensional form and surface undulations, outlines remain uniform and static, reinforcing graphic clarity rather than depth. The absence or presence of an outline significantly affects the visual language of an artwork, influencing its perceived realism, stylization, or abstraction.”

Oval

“A closed, curved shape that resembles an elongated or compressed circle but lacks a single, precise mathematical definition. While often used interchangeably with terms like ellipse in casual speech, an oval can refer to a wider class of rounded forms that are not necessarily symmetrical or governed by strict geometric rules.

In formal geometry, an ellipse is a specific type of oval defined as the set of all points for which the sum of the distances to two fixed points (foci) is constant. An oval, by contrast, may include asymmetrical curves, composite arcs, or freehand constructions that do not meet this definition.

In visual art and drawing, ovals are frequently used to approximate the circular cross-sections of cylinders, heads, eyes, and other rounded forms when seen in foreshortened or angled views. Unlike a true ellipse, which may be mechanically constructed, ovals in drawing are often intuitive, perceptual constructions that depend on context, orientation, and visual intention.

Ovals serve critical roles in: constructing pictorial ellipses (e.g., in cylinders, bowls, and wheels), defining volumetric relationships in form modeling (especially in portraiture), and managing rotational symmetry and curvilinear motion in layout and composition.

Because the term lacks a single geometric standard, it is important to understand oval in drawing and painting as a functional visual surrogate—a flexible, responsive shape used to simulate curvature and spatial continuity. In training contexts, artists are often guided to assess ovals not by ideal geometry, but by alignment, proportion, curvature continuity, and spatial consistency relative to perspective and form.

In short, an oval is a visually strategic shape, often free of rigid definition, that enables artists to represent complex curvatures and rotating planes in a perceptually legible manner.”

Overlapping Planes in Composition

“A compositional strategy where multiple layers of shapes or forms are arranged to create depth, hierarchy, and spatial separation within an image. Overlapping planes enhance depth perception by leveraging occlusion cues—when one object partially obscures another, the brain interprets the occluded object as being farther away. This powerful depth cue is independent of perspective or shading cues, making it a fundamental tool in both representational and abstract compositions. Artists use overlapping planes to create spatial relationships, direct focus, and build visual tension, while designers and filmmakers employ layering techniques to reinforce hierarchy and depth in visual storytelling.”

Oxidation

“In the context of oil painting, oxidation refers broadly to the chemical reaction by which the unsaturated fatty acids in a drying oil (such as linseed oil) react with atmospheric oxygen. This initial uptake of oxygen begins the transformation of the paint film from a fluid state to a solid one. Oxidation triggers the formation of hydroperoxides and unstable intermediates that lead to subsequent reactions such as polymerization and cross-linking. While the term describes any interaction involving the loss of electrons to oxygen, in oil painting, it serves as a general umbrella for the oxygen-driven processes that begin film curing. Importantly, oxidation includes—but is not limited to—the specific mechanism of auto-oxidation.”