La il·luminació i la proporcionalitat numèrica
 (Velázquez)

“La belleza no es casual. Sorprende ver la multiplicidad de cálculos y proporciones que hay en un cuadro de Velázquez y la belleza que a través de ello transmite. ¿Hay quizá una sensación de armonía universal en las proporciones que los matemáticos descubrieron, y los artistas lo aplicaron, que puede explicar que este concepto de belleza no casual? […] La organización del cuadro queda definida por unas líneas y rectángulos con proporciones pitagóricas y áureas. ¿Ingenio o técnica del pintor?”

“Light can reflect from a subject as a diffuse reflection, direct reflect, or polarized reflection. Most surfaces produce some of each of these three types. The proportions vary with the subject, and it is the proportions of the reflections in the mix that make one surface look different from another”.

“alcarraza, alcarraça, , arcarrasa. (Del ár. al-karrāz.) f. Vasija de arcilla porosa y poco cocida, que tiene la propiedad de dejar rezumarse cierta porción de agua, cuya evaporación enfría la mayor cantidad del mismo líquido que queda dentro”.

“Direct reflection strictly obeys the Law of Reflection, which states that the angle incidence equals the angle of reflectance. […] The surface of a photographic subject, however, is made up of an infinite number of points. A viewer looking at that surface sees each of these many different points as a slightly different angle. Taken together, these different angles make up the family of angles that cause direct reflection. […] Lighting glass, on the other hand, requires attention to the edges. Withoud good edge definition, transparent subjects tend to blend with de background. […] dark-field method… we now want the edge of the glass to be bright, there must be light at the far limits of the family of angles. The effective size of the background is the single most important […] The background must, of course, be large enough to fill the field of view. But if is it too large, it will extend into the family of angles that produce direct reflection on the edge of the glass. […] Ideally, the background should exactly fill the field of view the camera , no more and no less, Fortunately, this ideal is not strictly necessary in practice”.