There is a reduction in the visual adaptation rate to changing light intensities due to age. Recent research has shown that the number of older people affected with visual impairments causing low vision keeps growing. It has also been established that older adults have difficult seeing under low illumination and at night. Whilst notable eye diseases such as macular degeneration and glaucoma account for a larger percentage for causing visual impairments amongst the old, there has been an increase in people becoming visually impaired even in the absence of ocular diseases. The major effect on the aspect of multimedia processing is that they cannot have the full and enjoyable access to the multimedia and other digital contents that are available on conventional devices such as PCs, PDAs or even mobile phones. This document presents a tone mapping model that presents accurate simulations of temporal visual processing at different ages, and goes further to give a roadmap for adaptation of digital contents in MPEG-21 multimedia environment. Our approach in this research culminates from Pattanaik’s tone-mapping model by making extensions to temporal visual filtering with the help of decay functions, thereby simulating a reduction of visual response which comes with age. Our filtering model paves way and lays a foundation for future research to develop a more effective adaptation model that may further be used in developing visual content adaptation aids, and guidelines in MPEG 21 environment. We demonstrate our visual model using a High Dynamic Range image and the experiment results are in conversant with the psychophysical data from previous vision researches. We also present a visual adaptation model for the older population at specific ages.
The first part of this thesis document presents accurate perceptually-based visual simulations of High Dynamic Range images and the effect that age has on the temporal visual adaptation rate to various luminance intensities in nature.We envisage that this approach will enable visual aid manufacturers better understand the Human Visual System fostering efficient, and appropriate design of visual aids for different age-groups. The second presents an adaptation framework to varying luminance intensities in the real environment after a person has been initially statistically adapted to light of a constant intensity, e.g. darkness. The adaptation framework pointed out in this thesis is strictly conceptual and is yet to be verified with clinical experiments using real human subjects. However, it shows much potential as it conforms to the psychophysical data that has been found from previous vision researches. It is to be mentioned that the work on adaptation to high dynamic range image streams is in its infancy.
