The preferred system gamma is primarily determined by the ratio of dynamic range of the original scene and the displayed image.

Authors: Kane, D., Grimaldi, A., Zerman, E., Bertalmlo, M., Hulusic, V. and Valenzise, G.

Journal: IS and T International Symposium on Electronic Imaging Science and Technology

eISSN: 2470-1173

DOI: 10.2352/ISSN.2470-1173.2018.14.HVEI-508

Abstract:

The dynamic range of real world scenes may vary from around 102 to greater than 107, whilst the dynamic range of monitors may vary from 102 to 105. In this paper, we investigate the impact of the dynamic range ratio (DRratio) between the captured scene and the displayed image, upon the value of system gamma preferred by subjects (a simple global power law transformation applied to the image). To do so, we present an image dataset with a broad distribution of dynamic ranges upon various subranges ofa SIM2 monitor. The full dynamic range of the monitor is 105 and we present images using either the full range, 75% or 50% of this, while maintaining a fixed mid-luminance level. We find that the preferred system gamma is inversely correlated with the DRratio and importantly, is one (linear) when the DRratio is one. This strongly suggests that the visual system is optimized for processing images only when the dynamic range is presented correctly. The DRratio is not the only factor. By using 50% of the monitor dynamic range and using either the lower, middle or upper portion of the monitor, we show that increasing the overall luminance level also increases the preferred system gamma, although to a lesser extent than the DRratio. (Formula presented.) Arguably the greatest concern when displaying an ungraded real world image upon a given monitor is the mismatch between the dynamic range of a monitor and the original scene/image. For the professional SIM2 monitor it is common for images to be of a substantially lower DR than the monitor (the inverse tone-mapping problem), and for monitors that are currently in widespread usage, images frequently have a much greater dynamic range (the tone-mapping problem). The multiplication required to increase the dynamic range of the lowest dynamic range image in the Fairchild database for presentation on the SIM2 is 323, whilst the division needed to present the highest dynamic range image on a CRT is 152500. This may in part explain why a simple power law appears to be sufficient to solve the inverse problem [5], but not the tone-mapping problems where an array of more complex algorithms has been proposed. For the rest of this paper we shall define the dynamic range ratio DRratio as the dynamic range of the original scene over the dynamic range of the display device.

http://eprints.bournemouth.ac.uk/30367/

Source: Scopus

The preferred system gamma is primarily determined by the ratio of dynamic range of the original scene and the displayed image

Authors: Kane, D., Grimaldi, A., Zerman, E., Bartalmio, M., Hulusic, V. and Valenzise, G.

Conference: Human Vision and Electronic Imaging Conference, IS&T International Symposium on Electronic Imaging (EI 2018)

Dates: 29 January-1 February 2018

Abstract:

The dynamic range of real world scenes may vary from around 102 to greater than 107 , whilst the dynamic range of monitors may vary from 102 to 105 . In this paper, we investigate the impact of the dynamic range ratio (DRratio) between the captured scene and the displayed image, upon the value of system gamma preferred by subjects (a simple global power law transformation applied to the image). To do so, we present an image dataset with a broad distribution of dynamic ranges upon various subranges of a SIM2 monitor. The full dynamic range of the monitor is 105 and we present images using either the full range, 75% or 50% of this, while maintaining a fixed mid-luminance level. We find that the preferred system gamma is inversely correlated with the DRratio and importantly, is one (linear) when the DRratio is one. This strongly suggests that the visual system is optimized for processing images only when the dynamic range is presented correctly. The DRratio is not the only factor. By using 50% of the monitor dynamic range and using either the lower, middle or upper portion of the monitor, we show that increasing the overall luminance level also increases the preferred system gamma, although to a lesser extent than the DRratio.

http://eprints.bournemouth.ac.uk/30367/

Source: Manual