This study presents a methodology of forming contextually valid scales for subjective video quali... more This study presents a methodology of forming contextually valid scales for subjective video quality measurement. Any single value of quality e.g. Mean Opinion Score (MOS) can have multiple underlying causes. Hence this kind of a quality measure is not enough for example, in describing the performance of a video capturing device. By applying Interpretation Based Quality (IBQ) method as a
Image evaluation schemes must fulfill both objective and subjective requirements. Objective image... more Image evaluation schemes must fulfill both objective and subjective requirements. Objective image quality evaluation models are often preferred over subjective quality evaluation, because of their fastness and cost-effectiveness. However, the correlation between ...
Stereoscopic technologies have developed significantly in recent years. These advances require al... more Stereoscopic technologies have developed significantly in recent years. These advances require also more understanding of the experiental dimensions of stereoscopic contents. In this article we describe experiments in which we explore the experiences that viewers have when they view stereoscopic contents. We used eight different contents that were shown to the participants in a paired comparison experiment where the task of the participants was to compare the same content in stereoscopic and non-stereoscopic form. The participants indicated their preference but were also interviewed about the arguments they used when making the decision. By conducting a qualitative analysis of the interview texts we categorized the significant experiental factors related to viewing stereoscopic material. Our results indicate that realitylikeness as well as artificiality were often used as arguments in comparing the stereoscopic materials. Also, there were more emotional terms in the descriptions of the stereoscopic films, which might indicate that the stereoscopic projection technique enhances the emotions conveyed by the film material. Finally, the participants indicated that the threedimensional material required longer presentation time, as there were more interesting details to see.
We present an effective method for comparing subjective audiovisual quality and the features rela... more We present an effective method for comparing subjective audiovisual quality and the features related to the quality changes of different video cameras. Both quantitative estimation of overall quality and qualitative description of critical quality features are achieved by the method. The aim was to combine two image quality evaluation methods, the quantitative Absolute Category Rating (ACR) method with hidden reference
ABSTRACT To understand the viewing strategies employed in a quality estimation task, we compared ... more ABSTRACT To understand the viewing strategies employed in a quality estimation task, we compared two visual tasks-quality estimation and difference estimation. The estimation was done for a pair of natural images having small global changes in quality. Two groups of observers estimated the same set of images, but with different instructions. One group estimated the difference in quality and the other the difference between image pairs. The results demonstrated the use of different visual strategies in the tasks. The quality estimation was found to include more visual planning during the first fixation than the difference estimation, but afterward needed only a few long fixations on the semantically important areas of the image. The difference estimation used many short fixations. Salient image areas were mainly attended to when these areas were also semantically important. The results support the hypothesis that these tasks' general characteristics (evaluation time, number of fixations, area fixated on) show differences in processing, but also suggest that examining only single fixations when comparing tasks is too narrow a view. When planning a subjective experiment, one must remember that a small change in the instructions might lead to a noticeable change in viewing strategy. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
ABSTRACT The Dynamic Reference (DR) method has been developed for subjective image quality experi... more ABSTRACT The Dynamic Reference (DR) method has been developed for subjective image quality experiments in which original or undistorted images are unavailable. The DR method creates reference image series from test images. Reference images are presented to observers as a slide show prior to evaluating their quality. As the observers view the set of reference images, they determine the overall variation in quality within the set of test images. This study compared the performance of the DR method to that of the standardized absolute category rating (ACR) and paired comparison (PC) methods. We measured the performance of each method in terms of time effort and discriminability. The results showed that the DR method is faster than the PC method and more accurate than the ACR method. The DR method is especially suitable for experiments that require highly accurate results in a short time.
ABSTRACT The most common tasks in subjective image estimation are change detection (a detection t... more ABSTRACT The most common tasks in subjective image estimation are change detection (a detection task) and image quality estimation (a preference task). We examined how the task influences the gaze behavior when comparing detection and preference tasks. The eye movements of 16 naïve observers were recorded with 8 observers in both tasks. The setting was a flicker paradigm, where the observers see a non-manipulated image, a manipulated version of the image and again the non-manipulated image and estimate the difference they perceived in them. The material was photographic material with different image distortions and contents. To examine the spatial distribution of fixations, we defined the regions of interest using a memory task and calculated information entropy to estimate how concentrated the fixations were on the image plane. The quality task was faster and needed fewer fixations and the first eight fixations were more concentrated on certain image areas than the change detection task. The bottom-up influences of the image also caused more variation to the gaze behavior in the quality estimation task than in the change detection task The results show that the quality estimation is faster and the regions of interest are emphasized more on certain images compared with the change detection task that is a scan task where the whole image is always thoroughly examined. In conclusion, in subjective image estimation studies it is important to think about the task.
This study presents a methodology of forming contextually valid scales for subjective video quali... more This study presents a methodology of forming contextually valid scales for subjective video quality measurement. Any single value of quality e.g. Mean Opinion Score (MOS) can have multiple underlying causes. Hence this kind of a quality measure is not enough for example, in describing the performance of a video capturing device. By applying Interpretation Based Quality (IBQ) method as a
This study presents a methodology of forming contextually valid scales for subjective video quali... more This study presents a methodology of forming contextually valid scales for subjective video quality measurement. Any single value of quality e.g. Mean Opinion Score (MOS) can have multiple underlying causes. Hence this kind of a quality measure is not enough for example, in describing the performance of a video capturing device. By applying Interpretation Based Quality (IBQ) method as a
The subjective quality of an image is a non-linear product of several, simultaneously contributin... more The subjective quality of an image is a non-linear product of several, simultaneously contributing subjective factors such as the experienced naturalness, colorfulness, lightness, and clarity. We have studied subjective image quality by using a hybrid qualitative/ quantitative method in order to disclose relevant attributes to experienced image quality. We describe our approach in mapping the image quality attribute space in three cases: still studio image, video clips of a talking head and moving objects, and in the use of image processing pipes for 15 still image contents. Naïve observers participated in three image quality research contexts in which they were asked to freely and spontaneously describe the quality of the presented test images. Standard viewing conditions were used. The data shows which attributes are most relevant for each test context, and how they differentiate between the selected image contents and processing systems. The role of non-HVS based image quality analysis is discussed.
Subjective quality rating does not reflect the properties of the image directly, but it is the ou... more Subjective quality rating does not reflect the properties of the image directly, but it is the outcome of a quality decision making process, which includes quantification of subjective quality experience. Such a rich subjective content is often ignored. We conducted two experiments (with 28 and 20 observers), in order to study the effect of paper grade on image quality experience of the ink-jet prints. Image quality experience was studied using a grouping task and a quality rating task. Both tasks included an interview, but in the latter task we examined the relations of different subjective attributes in this experience. We found out that the observers use an attribute hierarchy, where the high-level attributes are more experiential, general and abstract, while low-level attributes are more detailed and concrete. This may reflect the hierarchy of the human visual system. We also noticed that while the observers show variable subjective criteria for IQ, the reliability of average subjective estimates is high: when two different observer groups estimated the same images in the two experiments, correlations between the mean ratings were between .986 and .994, depending on the image content.
Image evaluation schemes must fulfill both objective and subjective requirements. Objective image... more Image evaluation schemes must fulfill both objective and subjective requirements. Objective image quality evaluation models are often preferred over subjective quality evaluation, because of their fastness and cost-effectiveness. However, the correlation between ...
Test image contents affect subjective image-quality evaluations. Psychometric methods might show ... more Test image contents affect subjective image-quality evaluations. Psychometric methods might show that contents have an influence on image quality, but they do not tell what this influence is like, i.e., how the contents influence image quality. To obtain a holistic description of subjective image quality, we have used an interpretation-based quality (IBQ) estimation approach, which combines qualitative and quantitative methodology.
The estimation of image quality is a demanding task, especially when estimating different high-qu... more The estimation of image quality is a demanding task, especially when estimating different high-quality imaging products or their components. The challenge is the multivariate nature of image quality as well as the need to use naïve observers as test subjects, since they are the actual end-users of the products. Here, we use a subjective approach suitable for estimating the quality
The verbalization of one&... more The verbalization of one's thoughts has been shown to impair judgment and decision making in some cases, particularly when targets are perceptual. This finding has been attributed to the fact that non-verbal processes are sometimes difficult to verbalize, which may cause a shift in processing that is maladaptive to the task. The study shows that concurrent written explanations can also enhance judgment and decision making in certain visual choice tasks. This finding suggests that the effect of verbalization on perceptual tasks is not dependent on whether the targets of the judgment are verbal or perceptual but rather on whether there is adequate vocabulary to execute the task and whether the task benefits from a more analytic approach.
This study presents a methodology of forming contextually valid scales for subjective video quali... more This study presents a methodology of forming contextually valid scales for subjective video quality measurement. Any single value of quality e.g. Mean Opinion Score (MOS) can have multiple underlying causes. Hence this kind of a quality measure is not enough for example, in describing the performance of a video capturing device. By applying Interpretation Based Quality (IBQ) method as a
Image evaluation schemes must fulfill both objective and subjective requirements. Objective image... more Image evaluation schemes must fulfill both objective and subjective requirements. Objective image quality evaluation models are often preferred over subjective quality evaluation, because of their fastness and cost-effectiveness. However, the correlation between ...
Stereoscopic technologies have developed significantly in recent years. These advances require al... more Stereoscopic technologies have developed significantly in recent years. These advances require also more understanding of the experiental dimensions of stereoscopic contents. In this article we describe experiments in which we explore the experiences that viewers have when they view stereoscopic contents. We used eight different contents that were shown to the participants in a paired comparison experiment where the task of the participants was to compare the same content in stereoscopic and non-stereoscopic form. The participants indicated their preference but were also interviewed about the arguments they used when making the decision. By conducting a qualitative analysis of the interview texts we categorized the significant experiental factors related to viewing stereoscopic material. Our results indicate that realitylikeness as well as artificiality were often used as arguments in comparing the stereoscopic materials. Also, there were more emotional terms in the descriptions of the stereoscopic films, which might indicate that the stereoscopic projection technique enhances the emotions conveyed by the film material. Finally, the participants indicated that the threedimensional material required longer presentation time, as there were more interesting details to see.
We present an effective method for comparing subjective audiovisual quality and the features rela... more We present an effective method for comparing subjective audiovisual quality and the features related to the quality changes of different video cameras. Both quantitative estimation of overall quality and qualitative description of critical quality features are achieved by the method. The aim was to combine two image quality evaluation methods, the quantitative Absolute Category Rating (ACR) method with hidden reference
ABSTRACT To understand the viewing strategies employed in a quality estimation task, we compared ... more ABSTRACT To understand the viewing strategies employed in a quality estimation task, we compared two visual tasks-quality estimation and difference estimation. The estimation was done for a pair of natural images having small global changes in quality. Two groups of observers estimated the same set of images, but with different instructions. One group estimated the difference in quality and the other the difference between image pairs. The results demonstrated the use of different visual strategies in the tasks. The quality estimation was found to include more visual planning during the first fixation than the difference estimation, but afterward needed only a few long fixations on the semantically important areas of the image. The difference estimation used many short fixations. Salient image areas were mainly attended to when these areas were also semantically important. The results support the hypothesis that these tasks' general characteristics (evaluation time, number of fixations, area fixated on) show differences in processing, but also suggest that examining only single fixations when comparing tasks is too narrow a view. When planning a subjective experiment, one must remember that a small change in the instructions might lead to a noticeable change in viewing strategy. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
ABSTRACT The Dynamic Reference (DR) method has been developed for subjective image quality experi... more ABSTRACT The Dynamic Reference (DR) method has been developed for subjective image quality experiments in which original or undistorted images are unavailable. The DR method creates reference image series from test images. Reference images are presented to observers as a slide show prior to evaluating their quality. As the observers view the set of reference images, they determine the overall variation in quality within the set of test images. This study compared the performance of the DR method to that of the standardized absolute category rating (ACR) and paired comparison (PC) methods. We measured the performance of each method in terms of time effort and discriminability. The results showed that the DR method is faster than the PC method and more accurate than the ACR method. The DR method is especially suitable for experiments that require highly accurate results in a short time.
ABSTRACT The most common tasks in subjective image estimation are change detection (a detection t... more ABSTRACT The most common tasks in subjective image estimation are change detection (a detection task) and image quality estimation (a preference task). We examined how the task influences the gaze behavior when comparing detection and preference tasks. The eye movements of 16 naïve observers were recorded with 8 observers in both tasks. The setting was a flicker paradigm, where the observers see a non-manipulated image, a manipulated version of the image and again the non-manipulated image and estimate the difference they perceived in them. The material was photographic material with different image distortions and contents. To examine the spatial distribution of fixations, we defined the regions of interest using a memory task and calculated information entropy to estimate how concentrated the fixations were on the image plane. The quality task was faster and needed fewer fixations and the first eight fixations were more concentrated on certain image areas than the change detection task. The bottom-up influences of the image also caused more variation to the gaze behavior in the quality estimation task than in the change detection task The results show that the quality estimation is faster and the regions of interest are emphasized more on certain images compared with the change detection task that is a scan task where the whole image is always thoroughly examined. In conclusion, in subjective image estimation studies it is important to think about the task.
This study presents a methodology of forming contextually valid scales for subjective video quali... more This study presents a methodology of forming contextually valid scales for subjective video quality measurement. Any single value of quality e.g. Mean Opinion Score (MOS) can have multiple underlying causes. Hence this kind of a quality measure is not enough for example, in describing the performance of a video capturing device. By applying Interpretation Based Quality (IBQ) method as a
This study presents a methodology of forming contextually valid scales for subjective video quali... more This study presents a methodology of forming contextually valid scales for subjective video quality measurement. Any single value of quality e.g. Mean Opinion Score (MOS) can have multiple underlying causes. Hence this kind of a quality measure is not enough for example, in describing the performance of a video capturing device. By applying Interpretation Based Quality (IBQ) method as a
The subjective quality of an image is a non-linear product of several, simultaneously contributin... more The subjective quality of an image is a non-linear product of several, simultaneously contributing subjective factors such as the experienced naturalness, colorfulness, lightness, and clarity. We have studied subjective image quality by using a hybrid qualitative/ quantitative method in order to disclose relevant attributes to experienced image quality. We describe our approach in mapping the image quality attribute space in three cases: still studio image, video clips of a talking head and moving objects, and in the use of image processing pipes for 15 still image contents. Naïve observers participated in three image quality research contexts in which they were asked to freely and spontaneously describe the quality of the presented test images. Standard viewing conditions were used. The data shows which attributes are most relevant for each test context, and how they differentiate between the selected image contents and processing systems. The role of non-HVS based image quality analysis is discussed.
Subjective quality rating does not reflect the properties of the image directly, but it is the ou... more Subjective quality rating does not reflect the properties of the image directly, but it is the outcome of a quality decision making process, which includes quantification of subjective quality experience. Such a rich subjective content is often ignored. We conducted two experiments (with 28 and 20 observers), in order to study the effect of paper grade on image quality experience of the ink-jet prints. Image quality experience was studied using a grouping task and a quality rating task. Both tasks included an interview, but in the latter task we examined the relations of different subjective attributes in this experience. We found out that the observers use an attribute hierarchy, where the high-level attributes are more experiential, general and abstract, while low-level attributes are more detailed and concrete. This may reflect the hierarchy of the human visual system. We also noticed that while the observers show variable subjective criteria for IQ, the reliability of average subjective estimates is high: when two different observer groups estimated the same images in the two experiments, correlations between the mean ratings were between .986 and .994, depending on the image content.
Image evaluation schemes must fulfill both objective and subjective requirements. Objective image... more Image evaluation schemes must fulfill both objective and subjective requirements. Objective image quality evaluation models are often preferred over subjective quality evaluation, because of their fastness and cost-effectiveness. However, the correlation between ...
Test image contents affect subjective image-quality evaluations. Psychometric methods might show ... more Test image contents affect subjective image-quality evaluations. Psychometric methods might show that contents have an influence on image quality, but they do not tell what this influence is like, i.e., how the contents influence image quality. To obtain a holistic description of subjective image quality, we have used an interpretation-based quality (IBQ) estimation approach, which combines qualitative and quantitative methodology.
The estimation of image quality is a demanding task, especially when estimating different high-qu... more The estimation of image quality is a demanding task, especially when estimating different high-quality imaging products or their components. The challenge is the multivariate nature of image quality as well as the need to use naïve observers as test subjects, since they are the actual end-users of the products. Here, we use a subjective approach suitable for estimating the quality
The verbalization of one&... more The verbalization of one's thoughts has been shown to impair judgment and decision making in some cases, particularly when targets are perceptual. This finding has been attributed to the fact that non-verbal processes are sometimes difficult to verbalize, which may cause a shift in processing that is maladaptive to the task. The study shows that concurrent written explanations can also enhance judgment and decision making in certain visual choice tasks. This finding suggests that the effect of verbalization on perceptual tasks is not dependent on whether the targets of the judgment are verbal or perceptual but rather on whether there is adequate vocabulary to execute the task and whether the task benefits from a more analytic approach.
Uploads
Papers by Jenni Radun