There is a popular, half-jokey saying “that it is all done with mirrors” but there is a serious truth behind it in terms of pinning the three dimensional world down on a surface, a mirror is truly helpful. Before the invention of photography it was used in four important steps forward for art. For really accurate work Brunelleschi, who was a goldsmith by training and the inventor of modern perspective, chose to use polished silver as his mirror. This has two advantages - first that a sharp steel scribber can be used to plot the point where one plane turns to another with great accuracy. An obvious advantage for his first experiment in perspective, the drawing of the octagonal building of the Baptistry in Florence. Second the thickness of the glass of a normal mirror would have made this accurate plotting more difficult as one could not draw on the image itself. This use of burnished silver is confirmed by Manetti’s description of the painting, which he claims to have held in his hand many times.
For the other three examples a much bigger mirror is needed and I suggest a composite mirror or a large polished metal surface such as copper or pewter might have been used. What I take to be the first example of a large mirror image in a painting is now in the Louvre (a clad warrior with two mirrors c.1529 by Savoldo). Rembrandt was producing self-portraits from 1629 onwards but his first certain use of a large mirror would be the back view of Gertje Dircz (soon after 1642) where we see the mirror frame which is tall but not wide enough for some of my examples which need a mirror 8 ft wide. With Velasquez’s Las Meninas 1656 we need the same width but it is not difficult to imagine the royal Hall of Mirrors providing such a mirror though there is no record of the dimensions of those mirrors. Vermeer’s “The Love Letter” c.1670 shows us a mirror we take for a doorway but it has a normal mirror frame and heavy curtain to prevent light damage to the silver when the mirror is not in use. The mirror is around two and a half foot wide, which is enough for his purposes.
Rembrandt’s use of the mirror gave him the one advantage of getting a variety of images from one seat in the studio without disturbing the group from which his students were also working. In fact there is no doubt that the resulting works were nearly always inferior to those drawn direct from life.
Velásquez on the other hand gained a good deal. He had proved himself an exquisite observer of portraits but an unsure organiser of space (see Las Lanzas). His Las Meninas is regarded as his masterpiece achieved at the age of 56 it has been praised as “the theology of painting” yet he achieved it “more quickly than ever before” (J.Goudiol). Clearly the mirror helped him – in composition, by allowing him to compose the group within the mirror frame by moving his actors until he was satisfied they provided him with the optimum distribution in the room and within the limited space of the picture because he saw the image of the finished picture from the start – no guessing. The loss of light in a 17th C mirror gave him the further advantage of a limited range of tone closer to the range allowed by his paint.
With Vermeer using two mirrors the tonal range of light was doubly diminished ; two mirrors gave him the added advantage of being able to match his paint to the image seen in the second smaller mirror on his easel. So it is little wonder that he is admired for his mastery of light. The camera-obscura would also have had this advantage but the added disadvantages of very limited field and major complexity in operation (see Vermeer’s Camera by Steadman). I believe Vermeer used the camera-obscura solely for observing light out of focus.
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