[Paper Review] Visible Light-Based Human Visual System Conceptual Model

Lee Prangnell|arXiv (Cornell University)|Sep 15, 2016

Visual perception and processing mechanisms11 references3 citations

TL;DR

This paper proposes a Visible Light-Based Human Visual System (VL-HVS) conceptual model to reframe color perception in digital imaging by integrating physics of visible light, photoreceptor physiology, and cortical processing. It challenges the conventional focus on luma alone by advocating for balanced utilization of luma and chroma in image and video processing, enabling improved quantization and artifact reduction techniques grounded in a more accurate model of human color perception.

ABSTRACT

There exists a widely accepted set of assertions in the digital image and video coding literature, which are as follows: the Human Visual System (HVS) is more sensitive to luminance (often confused with brightness) than photon energies (often confused with chromaticity and chrominance). Passages similar to the following occur with high frequency in the peer reviewed literature and academic text books: "the HVS is much more sensitive to brightness than colour" and/or "the HVS is much more sensitive to luma than chroma". In this discussion paper, a Visible Light-Based Human Visual System (VL-HVS) conceptual model is discussed. The objectives of VL-HVS are as follows: 1. To provide a deeper theoretical reflection of the fundamental relationship between visible light, the manifestation of colour perception derived from visible light and the physiology of the perception of colour. That is, in terms of the physics of visible light, photobiology and the human subjective interpretation of visible light, it is appropriate to provide comprehensive background information in relation to the natural interactions between visible light, the retinal photoreceptors and the subsequent cortical processing of such. 2. To provide a more wholesome account with respect to colour information in digital image and video processing applications. 3. To recontextualise colour data in the RGB and YCbCr colour spaces, such that novel techniques in digital image and video processing, including quantisation and artifact reduction techniques, may be developed based on both luma and chroma information (not luma data only).

Motivation & Objective

• To provide a deeper theoretical foundation linking visible light, retinal photoreceptors, and cortical processing in human color perception.
• To offer a holistic understanding of color information in digital image and video processing applications.
• To reframe RGB and YCbCr color spaces by integrating luma and chroma data more equitably for improved processing techniques.
• To enable novel quantization and artifact reduction methods based on both luma and chroma, moving beyond luma-centric models.

Proposed method

• Develops a conceptual model integrating the physics of visible light, photobiological responses of retinal photoreceptors, and neural processing in the visual cortex.
• Analyzes the distinction between luminance (luma) and photon energy (chromaticity/chrominance) to clarify perceptual sensitivity.
• Recontextualizes color spaces such as RGB and YCbCr by emphasizing the equal importance of chroma alongside luma in perceptual modeling.
• Proposes that perceptual models should account for the full spectrum of visible light interactions with photoreceptors, not just luminance-based metrics.
• Uses theoretical and physiological evidence to argue against the dominance of luma in coding standards and suggests a paradigm shift in processing design.

Experimental results

Research questions

• RQ1 How do the physical properties of visible light and photoreceptor responses jointly shape human color perception?
• RQ2 Why is the current emphasis on luma over chroma in image and video coding potentially misleading?
• RQ3 What theoretical and physiological foundations support a more balanced treatment of luma and chroma in digital color representation?
• RQ4 How can a revised conceptual model of the human visual system improve quantization and artifact reduction in digital image and video processing?

Key findings

• The Human Visual System's sensitivity is fundamentally rooted in the interaction between visible light, photoreceptors, and cortical processing, not solely in luminance or brightness.
• The conventional assumption that the HVS is more sensitive to luma than chroma is oversimplified and potentially misleading when based on conflated terms like brightness and chromaticity.
• A more accurate model of human color perception requires integrating photoreceptor responses (especially S-cones) and spectral power distributions of light.
• Reframing color spaces to treat luma and chroma as equally important can lead to more perceptually accurate image and video compression techniques.