plein air landscape painting
Painting From Life vs. From Photos

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What is behind the illusion of transparency? How can artists make use of the effect?

I noticed the illusion of transparency in this photograph and it reminded me that the question of how we perceive transparent things is a hot topic in visual science.

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Scientists use stimuli like those below to study the question. The consensus is that the visual system will make an interpretation of transparency when it detects two independent types of forms in the same place. Gratings like those below are useful in this type of research because the repeating patterns construct a sense of a continuous surface that can be seen through. The repeating patterns of the waves in the photo above produce the required effect nicely.

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My colleague Robert Shapley of NYU pointed out to me that artists in ancient times used this same principle of repeating patterns to create the illusion of transparency. In this ancient Greek vase, the cloth appears transparent (perhaps translucent is a better word.) The effect is constructed by repeating patterns of the folds of the cloth, against which one can see the contour of the leg, for example.

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Transparency through pattern as a technique for creating illusion should hold a lot of potential for contemporary artists, but it has to be done properly to create the effect. Here is an example from David Hockney that, despite a lot of cues, produces a only a weak transparency effect. We can recognize a pool filled with water, but the figure seems more entangled in the white reflections on the surface than submerged under them. The bluish cast and lower contrast of the figure are not in themselves particularly compelling in creating the transparency illusion. Perhaps that was Hockney’s intention; I think the light lines in the water are patterns of sunlight reflecting off the bottom of the pool and the figure, not the surface of the water. If so it is not surprising that these lines “break” a transparency effect. By using a more convincing repeating surface pattern for the water, he could have created a stronger illusion of transparency if he wanted to.

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Have you ever created transparency effects using repeating patterns like the water ripples in the first photo or the cloth folds on the Greek vase as the primary transparency cue?