3D Vision Blog

A normal user's look into the world of 3D Stereo Technologies

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More on Ghosting and Brightness of the Asus VG278H 3D Monitor

November 9th, 2011 · 26 Comments · GeForce 3D Vision

The new Asus VG278H 3D Vision-ready 120Hz LCD monitor has an interesting option in the OSD menu that allows you to control the level of the 3D Lightboost and thanks to that I was able to try some interesting things. In the review of the Asus VG278H 3D monitor I have already mentioned that there are some things that you can do in order to improve the results you will get when using the monitor. One example for that is to reduce the Contrast level from the default setting of 76 to 55 in order to reduce the level of ghosting/crosstalk in stereo 3D mode without sacrificing too much of the brightness and that is possible thanks to the 3D Lightboost technology that increases the brightness level. I’ve used a colorimeter to measure the level of brightness with the different settings of the Contrast level with the Lightboost set to the maximum level and here are the results:

Contrast 100: 202 cd/m2
Contrast 76: 160 cd/m2
Contrast 55: 111 cd/m2

And here is the level of brightness with the default setting for Contrast of 76 and different level of the Lightboost setting, from completely off to the maximum:

Off: 85 cd/m2
+1: 90 cd/m2
+2: 95 cd/m2
+3: 102 cd/m2
+4: 111 cd/m2
+5: 120 cd/m2
+6: 128 cd/m2
+7: 136 cd/m2
+8: 144 cd/m2
+9: 152 cd/m2
Max: 160 cd/m2

Notice that from the Off state of the Lightboost technology to the maximum level there is almost a double increase of the brightness level and what Nvidia was saying for the new technology was that it will increase the brightness twice. So you can say that this claim is true. Notice that the level of brightness you get with the decreased Contrast to a setting of 55 is the same as the +4 state of the Lightboost setting together with the default setting for Contrast. So you are kind of halving the effectiveness of the Lightboost technology in order to further reduce ghosting/crosstalk.

In order to further reduce the ghosting in 2D mode as well you can also play with the Trace Free option of the monitor. The default setting of 60 is quite Ok (the left part of the image above), but increasing it to the maximum value of 100 you get better results (the right part of the image above). You can see from the high-speed photos taken from the PixPerAn test software that the fast moving objects are looking better and have less ghosting with a higher value of the Trace Free function.

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More About the Strange White Banding Within Recent 3D LCD Monitors

February 4th, 2011 · 5 Comments · GeForce 3D Vision

If you remember the review of the 23″ Planar SA2311W 3D monitor I did not too long ago, you should also remember the interesting effect I’ve observed in the photo above (the banding on the white color). After testing a more recent model, namely the 27-inch Acer HN274H 3D monitor I have also observed the same strange effect with my extreme stereo 3D crosstalk test photos…

The photo above is of the monitor showing the 3D test photo and not through the lens of the shutter glasses, so don’t use it to judge for level of ghosting as it is not intended for that, but it is to investigate the strange gradation of white I’ve noticed. This test 3D photo uses black on white for the two eyes as this makes the strange color gradation of the white to be most apparent and it turns out that this issue is somewhat related to the OverDrive function as well as the current level of brightness (the contrast setting) of the monitor. If I disable the OverDrive through the system menu the problem with the gradation of the white disappears, but in turn I get a lot of crosstalk which is to be expected. If I push the contrast setting (the brightness) of the display higher or lower there is also difference in the banding of the white with the white turning out to be completely even after a specific value.

Of course the black on white stereo 3D crosstalk test photos are an extreme case that should not normally happen in real world use scenarios or it will be very hard to be seen with normal stereoscopic 3D content displayed on the screen. Nevertheless I wanted to know exactly what is causing this strange behavior, how exactly it is related to the use of OverDrive and why it was not present in the previous 3D-capable LCD monitors that I’ve tested already. So I’ve been in contact with Planar to get the answers to this questions and they were very helpful in explaining the exact reasons, also confirming my observations regarding the OD and contrast settings. I’m going to quote the exact response I’ve got from Planar below:

I’m going to try to explain why banding can be seen with certain stereo test patterns on Planar’s 3D Vision monitor. First, the goal of stereoscopic visualization is to show the left image only to the left eye and the right image only to the right eye. We want to prevent residual of the left image showing up when the right image is displayed, and visa-versa. Because lines addressed near the top of the display have more time to settle than lines at the bottom of the screen, the display electronics need to drive pixels more aggressively to switch from left to right as you get closer to the bottom of the screen. The display electronics has some limitations, where it can’t change the “aggressiveness” on a line by line basis. There are finite steps that the current drive electronics can control. This causes the banding, which can be seen on test images with constant gray values in one eye and high contrast in the other eye. However, as you stated in the article, this artifact is difficult to see in normal stereoscopic images because you would very rarely have large areas of a common gray level with high contrast between the left and right eye. If such an image were exhibited it would be uncomfortable to view (on any 3D monitor) because of the large discrepancy between the two eyes. This banding issue is below the threshold of visibility in real world images; just when guys like you or me test the extremes.

You asked why banding can be seen in test images on the new panel and not on the older ones. The older panels used one overdrive value for the entire display. This resulted in low stereo crosstalk in the middle of the display, but noticeable ghosting at the top and bottom of the screen. The new SA2311W monitor has low stereo crosstalk across the entire screen.

As for the reason that changing the contrast setting can eliminate banding, consider that with a low contrast setting you would drive a normal image from 0 to 85% (for instance) of the range available. This leaves some headroom for LCD overdrive which is used to improve 3D quality by reducing stereo crosstalk. In this case, you would see banding when a black image is shown in one eye and a high gray level (white) image is shown in the other. When you increase the contrast setting, you eliminate the headroom for overdrive. All the white values may be driven near 100% so that banding disappears, but then you observe ghosting. In general, a lower contrast setting results in better 3D quality for normal images.

The bottom line is that the appearance of this strange effect is a result from the efforts being applied in order to reduce the level of crosstalk/ghosting we are getting on the more recent 3D monitors and in order to have less ghosting at the top and bottom of the screen as compared to the earlier models. As it was already mentioned, this strange behavior is observed only with extreme test conditions and should not be easily noticeable in real world usage scenarios. And the white banding in these test photos will most likely be something that we are going to be seeing a lot from now on in the new 3D monitors that are about to come later this year, but you should not be worried about that fact. The important thing is that we are getting less and less crosstalk/ghosting with newer 3D-capable LCDs, right… ;)

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Stereo 3D Display Crosstalk Test Photos With Some Results

December 14th, 2010 · 29 Comments · GeForce 3D Vision

I’ve prepared two sample stereoscopic 3D photos in a Side by Side (JPS) format for testing the level of crosstalk/ghosting on 3D-capable displays, you can see how the files look like in the small versions above and in order to download the JPS files just right click on them and and select “Save Target As”. As you can see the test photos contain a photo only in one side and the other side is filled with white and black color in order to make the level of crosstalk/ghosting more apparent and easily viewable. Just open the two photos and look only through the left lens (close your right eye) in order to see the part of the image that is “leaking” from the one intended for the other eye. You can take a photo through the left lens and post the results below, just like the following examples…

Here is how the two test photos look like through the 3D Vision glasses’ left lens on a Samsung 2233RZ 3D-capable LCD monitor. As you can see there is ghosting visible with both test photos and there is a bit more at the top and bottom of the screen. The crosstalk you see here is due to the slower response time of the pixels on the screen and it is different due to the difference in transition between the displayed color on the photo and the white and black (the two extremes).

The situation with the test photos on Panasonic Viera VT20E 3D HDTV is a bit different, as there is no visual ghosting seen in the transition to white, but there is some ghosting visible with the transition to black (with some yellowish tint due to the glasses). Generally the plasma TVs have faster response time, but they are not completely ghosting free either, still the situation is better than on 3D LCD monitors as you can see comparing to the results from the Samsung monitor above.

You are also more than welcome to download, try, document the results on your 3D-capable display and then post the photos in the comments below, so that we can get a batter comparison between different 3D computer monitors and 3D TV sets…

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