Cameras, especially cameraphones, are using a large panel of technologies, such as multi-frame stacking and local tone mapping to capture and render scenes with high dynamic range. ISO defined charts for OECF estimation and visual noise measurement are not really designed for these specific use cases, especially when no manual control of the camera is available. Moreover, these charts are limited to one measurement. We developed a versatile laboratory setup to evaluate image quality attributes, like autofocus, exposure and details preservation. It is tested in various lighting conditions, with several dynamic ranges up to 7EV difference within the scene, under different illuminants. Latest visual noise measurements proposed by IEEE P1858 or ISO-15739 are not giving fully satisfactory results on our laboratory scene, due to differences in the chart, framing and lighting conditions used. We performed subjective visual experiments to build a quality ruler of noisy grey patches, and use it as a dataset to develop and validate an improved version of a visual noise measurement. In the experiments we also studied the impact of different environment conditions of the grey patches to assess their relevance to our algorithm. Our new visual noise measurement uses a luminance sensitivity function multiplied by the square root of the weighted sum of the variances of the Lab coordinates of the patches. A non-linear JND scaling is applied afterwards to get a visual noise measurement in units of JND of noisiness.
With the publication of the second edition of the ISO 15739 Standard [1] in 2013 the measurement of “visual noise” became a normative part of the standard. Over the years the algorithm has proven to be useful and reliable for the judgement of the visibility of noise in images captured by digital cameras. Nevertheless a few aspects of the measurement procedures were questioned by some experts like e.g. the relation of the contrast sensitivity function (csf) for the luminance and the two chrominance channels. And the resulting weighting factors for the three channels also depend on the csf relation. In addition, some experts would like to use the more common CIELAB space instead of CIELUV. For these reasons the responsible ISO technical committee 42 working group 18 is looking into a revision of the visual noise section of the standard. This paper describes the procedure the group is undertaking to solve the remaining issues in the upcoming revision.