Why Red and Blue Were Common in Old 3D Glasses: An In-Depth Exploration

(preview image: )

The Current Norm for Anaglyph 3D

The current standard for Anaglyph 3D technology utilizes red and cyan filters, with red primarily assigned to the left eye. Historically, cheaper filter materials used in the monochrome era dictated the choice of red and blue for convenience and cost efficiency.

The Science Behind Eye Sensitivity

To understand why red and blue filters have dominated, consider the trichromatic theory of color vision. Human eyes contain three different types of photoreceptors: red, green, and blue (or blue, green, and red). While these receptors respond most strongly to their respective colors, they also have significant overlap:

Red and Green Receptors Response to Light

Red receptors respond strongly to red light and moderately to green light. Green receptors respond primarily to green light and moderately to both red and blue light. Blue receptors respond most strongly to blue light and moderately to green light.

This means that if you want to filter light from a picture, using red and blue ensures that each eye sees only one color. Both colors will similarly allow white light to pass through, making them suitable for the Anaglyph 3D effect.

The Evolution of 3D Display Technology

When displaying 3D images comes down to the use of three primary color sources: red, green, and blue. Yellow is created from an equal mixture of red and green. Orange light will appear bright when seen through a green filter and green light will appear distinct when seen through an orange filter, suggesting that neither pair (orange/green, purple/green) would be ideal for stereoscopic vision.

Interestingly, color blindness is more prominent among red-green color deficiencies. However, filtered red and green still work well for the most common forms of color blindness, making them a practical choice for 3D viewing.

Chromatic Cancellation and Ghosting

The red and cyan filters used in Anaglyph 3D rely on the principle of chromatic cancellation. When red light is seen through the cyan filter, it appears white, while cyan light seen through the red filter appears black. This allows the eyes to perceive two different images from one two-dimensional picture, effectively creating a 3D effect.

Efficiency and Image Crosstalk

In the visible spectrum, and among commonly available dyes and pigments, red and cyan are the most efficient for cross-cancelling each other, minimizing image crosstalk (ghosting). Ghosting refers to the faint appearance of the non-filtered view in each eye.

Comparison with Other 3D Technologies

While anaglyph 3D uses chromatic cancellation, other 3D technologies like polarized use different methods for cross-cancelling. For superimposed 3D systems, minimizing crosstalk is crucial, as filters must prevent each eye from seeing the view intended for the other eye.

Conclusion

Red and blue filters have long been a standard in 3D glasses due to their effectiveness in chromatic cancellation and their practicalities. While red and cyan have become the current norm, understanding the science and evolution of this technology helps explain why past 3D glasses were predominantly red and blue, setting the stage for the digital advancement we see today.