This series looks at two contrasting groups of paintings featuring reflections: those of figures seen mostly in planar mirrors arranged vertically, such as that mounted on a dressing table, and those of landscapes seen reflected by a horizontal water surface like a lake. When intended to be faithful to nature, these should all adhere to the same optical principles.
Introduction

Optical effects as a theme in the Northern Renaissance, as seen in Jan van Eyck’s most famous painting The Arnolfini Wedding, completed in 1434 (above), and in the landscape behind his Madonna of Chancellor Rolin, probably painted the following year (below).

Optics
Any faithful depiction of reflections on water should show the following:
- a line joining any point on the original with its equivalent on the reflection will be vertical;
- an object behind another object in the original will also remain behind that object in the reflection, as reflections preserve depth order;
- the further back that an original object is from the water’s edge, the more its reflection will be cropped vertically;
- vertical cropping loses the lower section of the original from the reflection, and the upper section remains in the reflection;
- the view of each part of the original seen in the reflection will be that as seen from the points of reflection, those being lower than the observer and closer to the original;
- what is seen on the (observer’s) left of the original appears on the left of the reflection, and what is seen on the right remains on the right of the reflection;
- because the reflection is vertically inverted, what is seen at the top of the original appears at the bottom of the reflection.
Analogous principles apply to reflections in a vertical mirror.
Reflection in a vertical mirror
Selfies
Self-portraits almost invariably rely on painting the reflection seen in a plane mirror.

The Venus Effect
Defined by Marco Bertamini, Richard Latto and Alice Spooner as occurring “every time the observer sees both an actor (eg Venus) and a mirror, not placed along the observer’s line of sight, and concludes that Venus is seeing her reflection at the same location in the mirror that the observer is seeing.” They were intrigued by “the situations in which we as observers read the scene in a certain way, but the mirror itself is used (deliberately or not) to lead us down the wrong path. More specifically, the mirror shows us something that we accept as the view available to the actor in the scene. However, the actor has a different vantage point from us and therefore the laws of optics imply that he/she cannot be seeing what we see in the mirror.”

Mirror Play
Where the artist manipulates a reflected image for an effect, whether or not that image remains faithful to optical principles.

Pierre Bonnard 1899-1908
Early mirror play by Pierre Bonnard (1867-1947).

Pierre Bonnard 1909-1946
Later mirror play by Pierre Bonnard (1867-1947).

Extending the image
Where the artist uses a reflection to show more of the motif than can be seen directly, often to add information when developing a story.

Reflection on a horizontal water surface
Northern landscapes
Paintings by:
Albrecht Dürer (1471-1528)
Aelbert Cuyp (1620–1691)
Nicolas Poussin (1694-1665), Landscape with a Calm (c 1651)
Claude Lorrain (1604/5–1682)
Canaletto (1697–1768)
Claude-Joseph Vernet (1714–1789)

Constable and Turner
Paintings by:
John Constable (1776–1837)
Joseph Mallord William Turner (1775–1851)

Realism in the late 19th century
Paintings by:
Gustave Caillebotte (1848–1894)
Martín Rico y Ortega (1833–1908)
Eilert Adelsteen Normann (1848–1918)
Laurits Andersen Ring (1854–1933)
Frits Thaulow (1847–1906)
Kazimierz Sichulski (1879–1942)

Impressionism
Paintings by:
Jean-Baptiste-Camille Corot (1796-1875)
Claude Monet (1840–1926)
Alfred Sisley (1839–1899)

Divisionism
Paintings by:
Georges Seurat (1859–1891)
Camille Pissarro (1830-1903)
Paul Signac (1863-1935)
Théo van Rysselberghe (1862-1926)

Cézanne
Paintings by Paul Cézanne (1839-1906)

Hodler and Klimt
Paintings by:
Ferdinand Hodler (1853–1918)
Gustav Klimt (1862–1918)

References
Brook Taylor (1719) New Principles of Linear Perspective, or the Art of Designing on a Plane the Representations of All Sorts of Objects, in a more General and Simple Method than has been done before, London. (Not available online, and later editions omit much of the material on reflections.)
Cole, Rex Vicat (1921) Perspective, Seeley, Service and Co, London. (Available in various reprints, and Archive.org.)
de Piles, Roger (1708) Cours de Peinture par Principes, Paris. (Available at Archive.org.)
de Valenciennes P-H (1820) Élémens de Perspective Pratique à l’usage des artistes, 2nd edn., Paris.
