TEST CASE 2: Van Eyck's Portrait of Cardinal Albergati 1431-2

Pictures were being copied very accurately around AD 1430. Did the artist have to use a lens or a mirror to make an accurate copy? Or were there simpler means that did not require optics? These questions allow us to explore if artists were using optical devices at that time.

Hockney and Falco identify in this painting the use of a concave mirror.

Sketch of Cardinal Albergati, van Eyck, 1431
Portrait of Cardinal Albergati, van Eyck, 1432
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Copies do exist of a portrait of Cardinal Albergati by the artist van Eyck. The Cardinal visited Bruges briefly in AD 1431, during which time van Eyck sketched him in silverpoint. Subsequently van Eyck used this sketch to paint a portrait of the Cardinal in oil paint, some 40% larger. When a copy of the sketch, enlarged by 40%, is superimposed on the painting, the agreement is exact, with two slight exceptions (discussed below). According to Falco and Hockney, such exact copying by van Eyck would only be possible using a concave mirror. Hockney's web site shows how this was achieved. This technique is that used in the modern epidiascope. A picture is illuminated and an image of it is formed using a concave mirror. The magnification achieved depends on the distance of the mirror from the subject and the image.

Hockney infers that van Eyck used the concave lens both to sketch the Cardinal and again later to enlarge the sketch to make the oil painting. As mentioned above, the sketch and the painting fail to match in two small regions - around the Cardinal's ear and around his collar. Either the sketch or the painting was knocked twice by accident during the transfer of the image. In both cases the displacement was no more than 4 mm. Then the match between the sketch and painting is exact overall, as shown on the web site.

Stork challenges Hockney and Falco's conclusion

Stork argues that accurate copies were possible by simpler means. Mirrors were not needed. Stork considers various options.

  1. It was drawn by eye. The agreement between the sketch and the painting is astonishingly good. Each minor and major feature agrees to within 1 mm. This seems impossible to achieve freehand. Before this possibility can be considered, it has to be demonstrated practically.
  2. It was drawn using the same type of grid that Durer used. Stork attributes the two displacements found in the matching of the sketch and the painting result from mis-counting of grid lines. The data do not support this. The displacements are not orthogonal and the numbers do not match. This notwithstanding, the grid only becomes a possible contender when its capability to produce an accurate copy is shown practically.
  3. It was drawn using a mechanical device - a pantograph or a Reductionszirkel. The pantograph is eliminated because it was not developed until 1600, The Reductionszirkel produces an inaccurate image.


Falco and Hockney have used a concave mirror to trace an image of a subject. They have yet to demonstrate that exact copies can be traced using this technique. Others have yet to demonstrate that exact copies can be produced using other techniques. We lack the information to make an informed decision. It does seem that van Eyck could have used a concave mirror to produce his portraits of Cardinal Albergati. At this time, no alternatives have been demonstrated.

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