Shade Variation and the Cornsweet Illusion: A dilemma of the Metal Composite Panels Manufacturing Industry

The Facade Installation Industry is abuzz with the discussion that concerns Shade Variation in Metal Composite Panels. Often confused with Colour Fading, Shading Variation is the occurrence of slight variations in aesthetics and appearances that are observed in different batches of the same Metal Composite Panels.

Before investing in Metal composite Panels, users must always keep in mind, these Check-Points that ensure long-lasting aesthetics:

1. The front-facing top part of the Metal Composite Panels must always be coated with PVDF or Lumiflon paint in 70:30 ratio of PVDF and Acrylic-based paints.
2. The Metal Composite Panels should always have a Two Coat paint application typically of 25-28 micron thickness or a Three Coat paint application of 30-35 micron thickness.
3. The Metal Composite Panels must be coated with high-quality paints that have been sourced from reputed brands like Hylar or Kynar.
4. Metal Composite Panels must be coated with paint using the Double Coat Double Bake methodology that ensures longevity and high staying power.
5. Metal Composite Panels can be installed using only Non-Bleeding Weatherproof Silicone Sealants.
6. Metal Composite Panels must be ordered as per the full requirement, at one go. For example, if there’s 1000sqm requirement for a particular shade of white-hued Metal Composite Panels, it must be ordered together and not in instalments so as to avoid Batch Variation in the shades.

If the chosen Metal composite Panels are as per the points mentioned above and even then also there seems to be a kind of shade variation like situation then the user must also check for the below points once.

If the chosen Metal Composite Panels match the checkpoints mentioned above and even then there seems to be a kind of shade variation like situation, then the user must also check for the below-mentioned pointers once:

1. Are there any curves/turns on the surface of the installation?
2. Is the façade straight or due to any manual/Fabrication error the Metal Composite Panels are not in a straight line?  

Cornsweet Illusion and Visual Perception

The above-mentioned pointers are major causes of Visual Illusion in Metal Composite Panels. The curved edges of Metal Composite Panels are the perfect example of Cornsweet Illusion.

In the1960’s Cornsweet Illusion was described by Tom Cornsweet and the topic was further described when published in 1970 in “Visual Perception”. The Cornsweet Illusion is an example of the way the brain uses the edges of shapes to impart information to the surrounding areas. It occurs due to the way nerve impulses travel through the visual cortex. The retina interprets what it sees using specific luminance profiles. Cornsweet image is processed with nearly identical codes, which the cortex then integrates and arrives at the same perceptual result. In other words, the brain is used to seeing things a certain way, and often interprets information within those parameters.

To refer to the picture above, both are the same shade of grey, and because of our brain’ perceived luminance distribution, one looks darker than the other. This effect usually happens when one panel is kept slightly above the other panel at a turn or curve.

The Cornsweet Illusion will be higher in metallic colours as compared to the solid colours due to the intensity of pigments and aesthetical differences.

Refer to the following images of the 3D Façade Installation which are a classic example of Cornsweet Illusion.

Image 1

Image 2