Μotion blur σε lcd tv's.Μύθος ή αλήθεια πλέον;

[gstriftos]

Ένα πολύ ενδιαφέρον άρθρο εδώ,για το εν λόγω φαινόμενο.

Σταχυολογόντας:

Although all display technologies have their own unique strengths and steadily improve over time, users' memories of their initial weaknesses and limitations can plague them forever. The best examples of this effect are plasma displays, with their so-called "burn-in" problem (which is actually uneven aging), something that was technically overcome many years ago but which lingers like an 800-pound gorilla that still threatens to kill this excellent technology. Plasma manufacturers bear much of the blame because they have chosen to avoid this issue in their marketing rather than confronting this widely held perception.
LCDs have their own gorilla: limited response time, which causes motion blur. As with plasmas and burn-in, this was a significant problem many years ago, and it too is no longer an issue now. But unlike plasma manufacturers, makers of LCDs have turned this into a brilliant marketing strategy, offering increasingly sophisticated and enhanced motion processing and ever higher 120- and 240-Hz screen refresh rates to repeatedly oversell a solution to a problem that is no longer a problem.

Findings Highlights

• <LI itxtvisited="1">Response time not a useful spec for indicating picture blur. <LI itxtvisited="1">Motion enhancement technologies can actually degrade image quality.
• Motion blur may be detectable in moving still images but not in even fast-moving video.

LCD Response Time and Motion Blur

Motion blur is a well-known issue with LCDs. It arises because the liquid crystal, the active element within an LCD, is unable to change its orientation and transmission rapidly enough when the picture changes from one frame to the next. Because the standard video rate is 60 frames per second (fps), a pixel is expected to be able to fully update its light transmission opacity within 16.7 ms (one-60th of a second). If it takes any longer than that, the image will show some degree of lag, which appears as a trailing smear or blur whenever there is motion. It also affects the visibility of the leading portions of moving objects.
LCD motion blur is generally evaluated with an industry-standard specification called response time. Unfortunately, it's not a particularly good indicator for real picture blur because it measures the time a pixel needs to go from black to peak-intensity white and then back again.

Figure 1 shows 11 HDTVs in the DisplayMate Technologies Demo Lab. Included are eight LCDs, two plasmas, and one Sony Professional HD Trinitron Studio Monitor, a CRT we used as the reference standard. This was an in-depth scientific study that included precise calibrations, comprehensive spectroradiometer measurements, and a large number of jury panelists that viewed test patterns, test photos, and high-quality HD video.

 

[gstriftos]

Σε κινούμενα patterns:

Moving Test Patterns
The first step in evaluating motion blur is to use specialized moving test patterns in order to cleanly examine and analyze the blur and related artifacts. To generate the moving test patterns and photographs we used DisplayMate Multimedia with Motion Bitmaps Edition, which includes 25 proprietary motion test patterns and 35 test photos that can be moved in different directions and speeds on screen. This digital video was fed simultaneously to all of the HDTVs, which were compared side by side in a shoot-out configuration as shown in Figure 1.

We used a Nikon D90 D-SLR to photograph the moving test patterns and photographs. The screenshots were taken with a shutter speed of 1/160th second, which is less than the refresh cycle time. These screenshots objectively measure the LCD display's own hardware blur, artifacts, and response time, and are consistent with what a human observer actually sees

Kινούμενες φωτογραφίες:

Moving Photographs
Test patterns are also perfectly valid images, no different in principle from any other image or picture content. Absolutely every effect, artifact, and defect that you see in any test pattern also appears in every image and picture. The difference is that test patterns are often constructed to maximize the visibility of specific effects, artifacts, and defects. That is the definitely the case with the DisplayMate motion test patterns used in the previous section, which were carefully designed and optimized to show the motion blur and artifacts.

Photographic images, on the other hand, typically consist of a very complex and varied admixture of blended picture elements. With so much going on in an image, motion blur is easily obscured and lost within the complex variegated imagery of a typical photograph. In particular, the photographs lack the uniform backgrounds used in the test patterns, which make it easier to see the motion blur trails. Still, from what we learned with the test patterns we expect to be able to see the effects of motion blur most easily when there are sharp bright-to-dark or black-to-dim transitions or strong-to-weak color saturation transitions.

Ζωντανή μετάδοση:

Though moving test patterns and photographs are very interesting and enlightening for studying motion blur and artifacts, live video is what consumers actually watch on their HDTVs. With even more screen activity we expect to visually detect much less motion blur in live video than with either the moving static photographs or test patterns. The first issue to consider is that there is no such thing as "typical" live video because of the incredible variety and diversity of content. Fortunately, we know from the moving test patterns and photographs what kinds of picture content are most likely to produce visible motion blur. And of course there needs to be lots of on-screen motion.

Most of the live video sources we chose were sports-based because they have lots of motion and most have brightly colored uniforms and background content. We recorded them on an all-digital high-definition Tivo from full-bandwidth over-the-air ATSC broadcast television. It directly records the original broadcast MPEG data stream without any processing or degradation. Note that satellite and cable video sources have reduced signal bandwidth that introduces additional motion artifacts because of the extra compression needed whenever there is motion in the picture. We also didn't use any film-based content, because it's shot at 24 fps and requires considerably more interpolation and motion processing than video cameras with 60 fields per second.

Συμπερασματικά:

Response time specifications are not a scientifically accurate or meaningful indicator of picture blur. In fact, in our tests the LCD with the shortest response time had the greatest motion blur. You'll see published values down to as little as 2 ms, but the motion blur we measured with moving test patterns on the top-of-the-line HDTVs was over 40 ms, which is more than a factor of 10 greater than the manufacturer's specifications.

We also found that the proprietary motion enhancement processing technologies provided in most HDTVs actually just introduce ugly motion artifacts into the image rather than reducing the overall visual motion blur. The best picture quality was obtained with the motion enhancement processing minimized or turned off.

After extensive side-by-side objective testing with moving test patterns, moving photographs and live video we found that there was no visually detectable difference in motion blur performance for current mid to top-of-the-line LCD HDTVs, regardless of their response time, 60- or 120-Hz refresh rates, strobed LED backlighting, or motion enhancement processing. While there was considerable motion blur in the moving test patterns, motion blur was simply not visually detectable in real live video content during our extensive side-by-side testing.

As a result, our bottom-line recommendations are: If you stick with the mid- to top-tier models from the reputable brands, you should ignore response time specifications, not worry about LCD motion blur, and not spend extra for 120-Hz or higher refresh rates, strobed LED backlighting, or advanced motion blur processing.

Ωρε τί λέει τούτος?

Dr. Raymond Soneira is president of DisplayMate Technologies Corporation of Amherst, New Hampshire, which produces video calibration, evaluation, and diagnostic products for consumers, technicians, and manufacturers.

Εσείς έχετε παρατηρήσει διαφορές,είτε προς το καλό ή το κακό όταν εφαρμόζονται τα ''κόλπα'' του πολλαπαλσιασμού των Hz για ομαλοποιήση της κίνησης?

Πρόσωπικά,με εξαίρεση τα 200άρια της Σόνυ,βρίσκω διαφορές,ειδικά σε αθλητικό τηλεοπτικό σήμα,πρός τομ χειρότερο.
Βέβαια σε αυτό ίσως και να φταίει το τηλεοπτικό μας σήμα.
Τι λέτε λοιπόν?:144:

 

[ironman]

Απάντηση: Μotion blur σε lcd tv's.Μύθος ή αλήθεια πλέον;

Σήμερα μιλούσα με φίλο που βλαστημά την ώρα και τη στιγμή που άλλαξε 37αρα φτηνή LG με 42 LΗ4000 αφού το τηλεοπτικό σήμα είναι απελπιστικά κακό.

Γενικός κανόνας: Δεν μπορούμε να τα έχουμε όλα ούτε -λυπάμαι αλλά έχω πάνω από 15 χρόνια στο hi fi & hi end και 10 στο home cinema, ΔΕΝ υπάρχουν giant killers...

Δεν έχω δει καλύτερο σύστημα από το Motionflow 200hz σε συνδυασμό με το Bravia Engine 3.

Από τη στιγμή που φύγαμε από τις "απλές" 50Hz το παιχνίδι παίζεται πολύ στο κομμάτι των ηλεκτρονικών. Τώρα δε που μπήκε και στο παιχνίδι και ο φωτισμός...

Θα ξεχωρίσουν οι άντρες από τα αγόρια...

It's an engineers game...