“With the metaperceptual helmets, we have tried to make aperfect loop of looking and being looked at, the project taking as a startingpoint the pioneering experiments in perceptual adaptation carried out bypsychologist George Malcolm Stratton. Wearing the helmets, the visitor becomesa hybrid creature: part human, part machine, part animal, but also part work ofart. A work of art that challenges those who contemplate the helmet– fromthe inside or from the outside– to take a new perspective on the world.” –Anne Cleary & Dennis Connolly, artist collaborators
This helmet was a new version of a technique originallypresented in 1988 at the Bristol ECVP that explored what the world looked likein pure colour, without the dark and light contrasts, and the contours, motionand depth given by luminance (Cavanagh, Adelson, &Heard, 1992). This is not easy to achieve because the same cones that giveus colour also let us see luminance. To do so, the information coming to thevisual system from the L and M (red- and green-sensitive) cones was blockedusing a bright yellow light covering the entire visual scene (e.g., Stiles, 1959; Wald, 1966). The Land M cones together provide luminance information, and the bright yellowdrives them to saturation, so they no longer respond differentially to spatialvariations that would normally activate them. With the L and M cones saturated,the only spatially varying signal came from the S cones (blue-sensitive) that supportprincipally the blue–yellow opponent-colour pathway (e.g., Eisner & MacLeod,1980). The visual information was also passed through a bluefilter to limit variations that would stimulate the L and M cones. This versionwas installed in a theatre in Bristol with the observers separated from thestage by a curtain, made of a deep blue filter and a veil lit from the auditorium side with intense yellow light. The audience could see objectsthrough this, but only in shades of equilumininous white and yellow. They couldmake out objects and people on the stage, but most observers saw the depth as flat, as if the scene were printed on the curtain. Motion slowed, often dramatically. A spinning wheel appeared to slow or even stop completely. Faceswere difficult to recognise. Subsequently, this stage version was presented atthe ChromaFest at the MIT Media Lab in 1990 and at VSS in Florida in 2004.
In our project, we built a helmet using a miniature versionof this technique. The first prototype was adapted from a welder’s mask. Theregular welding filter was replaced with one designed to behave like theequiluminising curtain of the stage versions. At the front, facing the scene,was a deep-blue filter (Lee 071). The filter had to cope with a range oflighting conditions, from artificial light to full sunlight, so we used twolayers of deep blue film, the second as a flap that could be pulled down insunlight. Behind this, we put an 8-mm-thick plexiglas panel, the surface scoredwith a 1 mm grid of lines (vertical lines on the front, horizontal lines on theback). Along the upper and lower edges of this panel, we installed LED strips(20 cm SMD-8020 LEDs 320-390 lm warm white) with yellow filters (Roscolux,Supergel R10), lighting the plexiglass so that the etched lines in the surfacelet out the internally reflected light and appear bright yellow, like the veilin the stage experiments.
We placed a dimmer switch on the outside to allow users tovary the intensity of the light so that it just saturated the L and M cones,making motion slow and depth collapse. We added a battery pack with eight 1.5 Vbatteries in series to provide 12 V to drive the LEDs. To give extra lightingcontrol, we added a switch to activate the top and bottom lights independently.The welder’s mask blocked the light from the front, other than that comingthrough the viewing screen, and we added a black shroud on the back to preventlight leaking in from behind.
The helmet appears to havecaptured the main properties reported for the much larger stage versions. Itcould help to explore the properties of S cone-based vision in natural scenesand may be a useful addition to teaching and research projects at the universitylevel concerning colour and vision at equiluminance (Gregory, 1977;Cavanagh, Anstis, &MacLeod, 1987).