After I posted various reports about the documentary film Tim’s Vermeer, a few readers encouraged me to give a scholarly assessment of Jenison’s claim that Vermeer had used an optical device called a comparator mirror as an aid to his painting. Given my limited knowledge of the use of optics in seventeenth-century painting, I found it more appropriate to examine the issue from a technical viewpoint, since I am by profession a painter. The fact that I have studied Vermeer’s painting technique and attempted to emulate his manner for over 40 years, I hope, might give me a discreet edge over non-painters in evaluating if Jenison’s device is or is not compatible with what we know of Vermeer’s pictorial strategy and technical procedures.
Following some lively discussions with Mr. Jenison on the finer points of Vermeer’s painting procedures, I was able to meet him in Texas and experiment with the comparator mirror on the premises of a full-scale mockup of scene of Vermeer’s Music Lesson which Jenison had built in order to test his hypothesis by paintings his own Vermeer.
My first attempt to use the comparator mirror was frustrating. Not only was I unable to produce acceptable pencil outlines of a black and white photograph with which Jenison had used in his first experiments, I was utterly incapable of matching on paper any of the photograph’s tonal values. To use the comparator, at least as I was attempting to use it at the moment, one is constrained to work within an extremely small area of the drawing, along a thin edge where the image of the comparator mirror abuts on the drawing below and the two can be compared. Initially I found this procedure mentally and visually stressing, and at odds with my experience in conceiving and making paintings.
With a little more practice I was able to produce a few acceptable contours, even though they lacked any sort of artistic quality. However, seeing that I am not particularly skilled with a pencil, I though it best to test the device with paint and brush with which I have greater familiarity, even though on first consideration the oil painting technique seemed even more at odds with the mirror’s limitations than with dry drawing.
Surprisingly, I made rapid progress with the oil medium. Although with a certain fatigue, I learned to define first simple and then complex contours with a fine-tipped brush and began, even more surprisingly, I marveled at how it was possible to match with utmost precision both the chromatic and tonal values of my painting with those of the mirror in a completely objective manner.
Having made substantial progress in coordinating mind, eye, brush and mirror after a few painting sessions, I started afresh and began to depict a small portion of Jenison’s Vermeer mockup Vermeer room following what I have come to understand of Vermeer’s multi-step painting technique. Beginning with a schematic line drawing which served to fixed the most salient contours of the scene, I first underpainted the lights and darks with monochrome brown (raw umber plus black) and white paints without, however, systematically consulting the comparator mirror. I was, in fact, interested in testing how close I could get to the correct values on my own.
Once the underpainting was thoroughly dry, I began to apply the final colors over it using thick opaque paint in the lights and thinner paint in the shadows, according to seventeenth-century prescription. In order to render a given passage I first mixed, as all painters do, the proper paints on the palette attempting to match them as closely as possible to the color and tonal value combining what I perceived in nature with I had learned through practice. I then applied the mixture to the canvas and compared the values of my paint to those of the corresponding passage in the mirror. I sometimes discovered that both the color and tone of my mixture were very close to those seen in the mirror, but just as often I was struck by how poorly I had interpreted nature notwithstanding my decades of experience. In a back and forth manner I was able to register the erred values of my work with those of the mirror and return to painting. Once the proper values were firmly in place, I freehanded most of the modelling as I would have done without using an optical aid, taking care to verify the accuracy of my progress via the comparator mirror at regular intervals. The comparator mirror was also of help in verifying difficult contours and defining the smallest details that I had been unable to capture by freehand.
In any case, once I had registered the values of my painting with those of the mirror, the passage appeared much more true to life (painters simply say “right”).
Although the set of mirrors and lens (Jenison’s used a double convex lens of the camera obscura in coordination with a concave mirror and a comparator mirror) requires periodic adjustments in order to view the different areas of the scene, this does not unduly interrupt the painting process once one has acquired the necessary skill maneuver them.
Conclusion
Given Jenison’s complete lack of painting experience, he painted his Vermeer employing the comparator mirror, as would be expected, in the most literal of manners. He painstakingly matched what he saw in the mirror with paint applied directly, alla prima, forgoing any sort of layering techniques that we know Vermeer and his more accomplished colleagues sometimes employed. This aspect of Jenison’s approach provoked considerable criticism, including my own. It was reasoned that Vermeer could not have used the comparator mirror because Jenison’s essentially paint-by-numbers technique, and the consequential one-layer paint structure gotten by such an approach, is completely at odds with the multi-layered structure of Vermeer’s paintings.
According to my experience the comparator mirror neither dictates nor limits the painter to any fixed procedure or techniques, including those used by Vermeer. Certainly, it would interfere no more with the creative painting process than a systematic use of the camera obscura.
If it is used in a “painterly” manner, as any experienced painter would be naturally inclined to do, the comparator mirror opens the possibility to study color more precisely than can be done with the camera obscura alone and allows the artist to match with remarkable efficacy the illusive tonal values of nature, which in effect are crucial to Vermeer’s unique brand of realism. Furthermore, I discovered that the erred tonal values of my monochrome underpainting did not compromise the rendering of the proper tones and colors of the final paint layers. The aim of seventeenth-century underpainting, as I understand it, was not to establish the precise tonal values of the final work from the very beginning, but rather to approximate the distribution of darks and lights thereby creating a sort of compositional blueprint which provided a solid base on to which the successive layers of colored paint could be applied in a more efficient manner. Although I used the glazing technique in only one passage (red madder over an underpainting of vermillion), it was evident that with some practice it would be relatively easy for any practiced painter to anticipate the tonal and chromatic values of the colored underpainting so they might eventually match those made visible in the mirror once the passage had been glazed with the final color.
The use of such a simple device as the comparator mirror in tandem with the camera obscura lens, in my opinion, is technically compatible with Vermeer’s known painting techniques (to be distinguished from his “pointillist” mannerism), and it is in line with what Lawrence Gowing appropriately called the artist’s “optical way” as well as the artist’s search for absolute tonal authenticity.