Description

With the advent of computational photography, most cellphones include High Dynamic Range (HDR) modes or “apps” that capture and render high contrast scenes in-camera using techniques such as multiple exposures and subsequent “addition” of those exposures to render a properly exposed image. The results from different cameras vary. Testing the image quality of different cameras involves field-testing under dynamic lighting conditions that may involve moving objects. Such testing often becomes a cumbersome and time-consuming task. It would be more efficient to conduct such testing in a controlled, laboratory environment. This study investigates the feasibility of such testing. Natural exterior scenes, at day and night, some of which include “motion”, were captured with a range of cellphone cameras using their native HDR modes. The luminance ratios of these scenes were accurately measured using various spectro-radiometers and luminance meters. Artificial scenes, which include characteristics of the natural exterior scenes and have similar luminance ratios, were created in a laboratory environment. These simulated scenes were captured using the same modes as the natural exterior scenes. A subjective image quality evaluation was conducted using some 20 observers to establish an observer preference scale separately for each scene. For each natural exterior scene, the correlation coefficients between its preference scale and the preference scale obtained for each laboratory scene were calculated, and the laboratory scene with the highest correlation was identified. It was determined that while it was difficult to accurately quantify the actual dynamic range of a natural exterior scene, especially at night, we could still simulate the luminance ratios of a wide range of natural exterior HDR scenes, from 266:1 to 15120:1, within a laboratory environment. Preliminary results of the subjective study indicated that reasonably good correlation (0.8 or higher on average) was obtained between the natural exterior and laboratory simulated scenes. However, such correlations were determined to be specific to the type of scene studied. The scope of this study needs to be narrowed. Another consideration, how moving objects in the scene would affect the results, needs further investigation.

Date of creation, presentation, or exhibit

1-31-2017

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Comments

This paper was presented at the IS&T Symposium on Electronic Imaging 2017.

Document Type

Conference Proceeding

Department, Program, or Center

School of Photographic Arts and Sciences (CAD)

Campus

RIT – Main Campus

Share

COinS