f = CFF
E = eccentricity in degrees
Li = retinal illuminance in Troland (Td = 10,000 cd/m2),
d = stimulus diameter in degree
f = CFF
E = eccentricity in degrees
L = eye luminance in Troland,
d = stimulus diameter in degree
p = pupil area in mm2
ScepticMatt wrote:centered eye: CFF = 89 Hz
35 degree right/left: CFF = 127 Hz
Chief Blur Buster wrote:So I'm pretty curious:
-- Are there any major studies done on the "1%" of the most sensitive humans (e.g. people least tolerant to CRTs, people least tolerant to VR, people least tolerant to motion blur, etc)
-- Are there any major studies done on the persistence-versus-motion-blur tradeoff? More specifically any discomfort caused by flicker, versus any discomfort caused by motion blur?
The weekly incidence of headaches among office workers was compared when the offices were lit by fluorescent lighting where the fluorescent tubes were operated by (a) a conventional switch-start circuit with choke ballast providing illumination that pulsated with a modulation depth of 43-49% and a principal frequency component at 100 Hz; (b) an electronic start circuit with choke ballast giving illumination with similar characteristics; (c) an electronic ballast driving the lamps at about 32 kHz and reducing the 100 Hz modulation to less than 7%. In a double-blind cross-over design, the average incidence of headaches and eyestrain was more than halved under high-frequency lighting. The incidence was unaffected by the speed with which the tubes ignited. Headaches tended to decrease with the height of the office above the ground and thus with increasing natural light. Office occupants chose to switch on the high-frequency lighting for 30% longer on average.
ScepticMatt wrote:About motion blur, I'm not sure. A quick search only turned up some studies of the headache inducing effects of ghosting in stereo vision.
Within this zone of comfortable viewing, visual discomfort may still occur to an extent, however, which is likely to be caused by one or more of the following three factors: (1) temporally changing demand of accommodation-vergence linkage, e.g., by fast motion in depth; (2) 3D artifacts resulting from insufficient depth information in the incoming data signal yielding spatial and temporal inconsistencies; and (3) unnatural blur.
ScepticMatt wrote:Relying on anecdotal evidence is a slippery slope, and should only be used in lieu of more solid evidence. All too often selection bias, preference, placebo or self-fulfilling prophecy ruin the cogency of the results.
ScepticMatt wrote:Looking a bit more into it, so far inability to accommodate could be the explanation for eye strain and fatigue caused by screen blur.
Here is a study showing the effects of out of focus screens:
http://www.cs.sfu.ca/CourseCentral/820/ ... ort-09.pdf
Any idea what additional research keywords for "motion blur" I could look for?
Chief Blur Buster wrote:-- Any other papers you've found, based on search terms I've suggested, that are new enough to cover strobe backlight behavior?
-- Any scientific paper on any adjustable-persistence displays?
-- Any scientific paper on fast-response displays where GtG/transition/pixel movement is an insignificant factor and persistence is the dominant factor of motion blur? (e.g. squarewave transitions)
-- Any scientific paper that contains/confirms the simple persistence formula (or a derivative thereof) that I've discovered, 1ms persistence = 1 pixel of motion blur during 1000 pixels/second? (I've begun to call this a Blur Busters Law, due to its reliably repeatable observations on strobe-backlight monitors).
Liquid crystal displays (LCD) are currently replacing the previously dominant cathode ray tubes (CRT) in most vision science applications. While the properties of the CRT technology are widely known among vision scientists, the photometric and temporal properties of LCDs are unfamiliar to many practitioners. We provide the essential theory, present measurements to assess the temporal properties of different LCD panel types, and identify the main determinants of the photometric output. Our measurements demonstrate that the specifications of the manufacturers are insufficient for proper display selection and control for most purposes. Furthermore, we show how several novel display technologies developed to improve fast transitions or the appearance of moving objects may be accompanied by side–effects in some areas of vision research. Finally, we unveil a number of surprising technical deficiencies. The use of LCDs may cause problems in several areas in vision science. Aside from the well–known issue of motion blur, the main problems are the lack of reliable and precise onsets and offsets of displayed stimuli, several undesirable and uncontrolled components of the photometric output, and input lags which make LCDs problematic for real–time applications. As a result, LCDs require extensive individual measurements prior to applications in vision science.
Due to the sample-and-hold nature of liquid crystal display (LCD) image formation, LCDs suffer from motion picture blur. This is especially evident during scenes containing fast motion due to the inherent sample-and-hold nature of LCD image formation. Using models for the human visual system (HVS) we take a signal processing approach to solving this problem by pre-processing the data before it is sent to the display. Whereas previous pre-processing approaches either apply a simple high pass filter or an iterative deconvolution algorithm, this work uses a small collection of efficient linear FIR filters to reduce the amount of perceived motion blur. Specifically, we develop a two-channel non-perfect reconstruction filter bank to reduce the motion dependent low pass effects of the HVS. Perceptual tests indicate that our algorithm reduces the amount of perceived motion blur on LCDs at a lower complexity than the existing deconvolution approach.
Motion blur is one of main challenges for using LCDs in television applications. An effective method for reducing the motion blur by blind signal processing was proposed. In this method, the LCD motion blur images are obtained by the MPRT(Motion Picture Response Time), and the motion vectors are estimated using the cepstral method, then the motion vectors are used in a pre-model for LCD motion blur image, and finally an initialization point spread function(PSF) of blind deconvolution can be constructed. The simulation results show that the proposed blind deconvolution can significantly reduce the visible blurring artifact on LCD.
It has been recognized for some time now that LCD displays will introduce blur when showing moving objects or moving images. Common motion-blur measurement methods permit to picture the blurred profile of an edge moving with a constant velocity. A normalized blurred edge width is then measured for several gray- to-gray transitions to give a motion-blur score of the display under test. However, these objective measurements are partly based on the behavior of the human visual system and it is an open question how well they correlate with subjective experience of observers. In this study, we develop a subjective experiment in order to assess the annoyance and the acceptance of motion-blur. Results are given and compare with measurements data.
Abstract— Compared to the conventional cathode-ray-tube TV, the conventional liquid-crystal TV has the shortcoming of motion blur. Motion blur can be characterized by the motion-picture response-time metric (MPRT). The MPRT of a display can be measured directly using a commercial MPRT instrument, but it is expensive in comparison with a photodiode that is used in temporal-response (temporal luminance transition) measurements. An alternative approach is to determine the motion blur indirectly via the temporal point-spread function (PSF), which does not need an accurate tracking mechanism as required for the direct “spatial” measurement techniques. In this paper, the measured motion blur is compared by using both the spatial-tracking-camera approach and the temporal-response approach at various backlight flashing widths. In comparison to other motion-blur studies, this work has two unique advantages: (1) both spatial and temporal information was measured simultaneously and (2) several temporal apertures of the display were used to represent different temporal PSFs. This study shows that the temporal method is an attractive alternative for the MPRT instrument to characterize the LCD's temporal performance.
One of the image quality issues of LC TV is the motion blur. In this paper, the LCD motion blur is modeled using a frequency domain analysis, where the motion of an object causes temporal component in the spatial/temporal spectrum. The combination of display temporal low-pass filtering and eye tracking causes the perception of motion blur. One way to reduce motion blur is to use backlight flashing, where the shorter "on" duration reduces the display temporal aperture function, thus improves the temporal transfer function of the display. The backlight flashing was implemented on a LCD with a backlight system consisting of an array of light emitting diodes (LED). The LED can be flashed on for a short duration after LCD reaches the target level. The effect of motion blur reduction was evaluated both objectively and subjectively. In the objective experiment, the retina image is derived from a sequence of captured images using a high speed camera. The subjective study compares the motion blur to an edge with a simulated edge blur. The comparison of objective and subjective experiments shows a good agreement. Both objective measurement and subjective experiment shows clear improvement in motion blur reduction with synchronized backlight flashing.
Abstract—Liquid crystal display (LCD) devices are well known for their slow responses due to the physical limitations of liquid crystals. Therefore, fast moving objects in a scene are often perceived as blurred. This effect is known as the LCD motion blur. In order to reduce LCD motion blur, an accurate LCD model and an efficient deblurring algorithm are needed. However, existing LCD motion blur models are insufficient to reflect the limitation of human eye tracking system. Also, the spatiotemporal equivalence in LCD motion blur models has not been proven directly in the discrete two-dimensional spatial domain, although it is widely used. There are three main contributions of this paper: modeling, analysis and algorithm. First, a comprehensive LCD motion blur model is presented, in which human eye tracking limits are taken into consideration. Second, a complete analysis of spatio-temporal equivalence are provided and verified using real video sequences. Third, an LCD motion blur reduction algorithm is proposed. The proposed algorithm solves an l1-norm regularized leastsquares minimization problem using a subgradient projection method. Numerical results show that the proposed algorithm gives higher PSNR, lower temporal error and lower spatial error than motion compensated inverse filtering (MCIF) and LucyRichardson deconvolution algorithm, which are two state-of-theart LCD deblurring algorithms.
The extent of perceived blur produced by a moving retinal image is less when the image motion occurs during pursuit eye movements compared to fixation. This study examined the effect of this reduced perception of motion blur during pursuit on spatial-interval acuity. Observers judged during pursuit at 4 or 8 deg/s whether the horizontal separation between two stationary lines was larger or smaller than a standard. Three different line separations were tested for each pursuit velocity. Each observer performed these judgments also during fixation, for spatial-interval stimuli that moved with the same mean and standard deviation of speeds as the distribution of eye velocities during pursuit. Spatial-interval acuity was better during pursuit than fixation for small or intermediate line separations. The results indicate that a reduction of perceived motion blur during pursuit eye movements can lead to improved visual performance.
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