| Author | Message | ||
     Anonymous Rating: N/A |
saw this over at guru3d.com Hitachi 17-inch LCD for gamers Hitachi America announced a new 17-inch CML174 LCD monitor with claimed twice lower response time than most of current LCDs. Rise time is 12 ms, Fall time 4 ms, the contrast ratio is a cool 400:1 and a recommended resolution of 1280x1024@75 Hz or 60 Hz. Shipments can be explected around November 8th with a suggested price of (yikes) .. $699 While it's not enough for stereo, a true 60Hz LCD flat panel is a good step forward. | ||
| Anonymous Rating: N/A |
A step but I don't know if you could call it a good one. I'd guess you're gonna have pretty much flicker. | ||
| Anonymous Rating: N/A |
even at acceptable refresh rates of 85 Hz or higher, it still wouldn't work. Aren't they inherrently different to the point that they will never work without serious changes? | ||
| Anonymous Rating: N/A |
Not sure about the heavy flicker, the 3D TV/DVD glasses that are selling are made for TVs running at 60Hz, which is far better than the 60Hz on a VGA screen. The technologies are different, you can't compare apples with bananas. | ||
| Anonymous Rating: N/A |
What about the ghosting? Won't it be the problem on every LCD monitors? | ||
| Andreas Schulz Rating: N/A |
I guess we're talking about shutter glasses here - nobody thought about the polarizers ? I've just got one TFT, but a handful of different shutter glasses to check: With all but the old Wicked3D glasses, the TFT screen through the glasses is almost pitch black (so no need to worry about ghosting ;-), since the polarizers of TFT and glasses are crossed. Don't know if there is any standard for the outgoing polarization of TFT's, so for other TFT's the situation may be reversed (or tilted somehow). Guess that's what Anonymous-08:33 was thinking about. | ||
| nichky Rating: N/A |
yes, that was me and that is what I am thinking about. The polarization needs to be reversed, which is a process i am not familiar with, nor have i heard anything about. If it were possible to adjust the polarization, it may be possible to begin using shutter glasses on the high end LCDs that are capable of 85+ hz | ||
| Anonymous Rating: N/A |
There has to be some 3D LCD glasses that work. It's not a problem to rotate the lenses and I can't believe that all hundreds (ok, maybe not that many) 3d glasses models are polarized in the same direction. | ||
| Andreas Schulz Rating: N/A |
OK, I was thinking about arbitrary combinations of shutter glasses and TFT screens in general. Rotating the panels 90 deg. in stock glasses I wouldn't call easy ;-) Of course, if a TFT company should start selling glasses bundled with their monitors (as e.g. ADI tried some time with some CRT monitors), they should be able to get the polarization right. Shutters with TFTs will even have the advantage that you will not loose brightness (as with CRTs), since the TFT's output comes polarized already. Ghosting wouldn't be a problem either, as long as screen and glasses are in sync, since the speed should be similar (except for ghosting caused by glasses not getting 100% black), in contrast to the afterglow of CRT monitors. That leaves first the problem of flicker - with 85Hz page-flipped, all you get is 42.5Hz per eye, resulting in noticable flicker (to say the least) - though I occasionally play stereo games at 1280*960/85Hz, it's not much fun... Last, but definitely not least at all, comes the way the incoming video signal (digital or analog) is processed by the TFT controller, i.e. how an incoming page-flipped stream will reach the TFT pixels. If the TFT controller isn't optimized for page-flip display, I'm afraid it may drop or interpolate frames, thus destroying the stereo information (any detailed information about this, anyone ?). Hmm, first thought that putting the stereo drivers on my wife's new PC (with TFT) was pointless, but I guess I will have to convince her to let me do some testing at least.. | ||
| Anonymous Rating: N/A |
The flicker problem is unknown for LCD panels, because running 60Hz on a TV or VGA screen is very different, where the VGA is much more flickerish. I've tried 3D glasses on CRT projectors too running at below 90Hz which I thought was about as good as 100+Hz on a VGA screen. You can't compare 2 different technologies straight up. Yeah, singnal processing might be a huge problem, maybe there is none if you use a digital input and match the refresh of the panel. | ||
| nickyj Rating: N/A |
andreas, please keep us posted with your testing. I'm very keen to hear if you make any progress. | ||
| Andreas Schulz Rating: N/A |
Well, for a start some findings about polarized output of TFT's; I've checked a few different brands at the office and in a shop: Only one or two had vertical (or horizontal) polarization like my wife's 333 EUR 15", i.e. they would match perfectly with my old Wicked3D glasses, but fail with most other glasses. Most other TFTs had diagonal, usually ca. 45 deg, orientation, except for one pivot-able Philips 18" model with ca. 30 deg. | ||
| nickyj Rating: N/A |
That's very interesting, but wicked 3D used the H3D hardware, and that technology is still being utilized by many of the manufacturers today. Also, did you actually try your wicked glasses out on them and if so, did it work, it simply had more than tolerable flicker? | ||
| Andreas Schulz Rating: N/A |
Not yet, just had a glance at the TFTs through the inactive glasses to check the polarization. Have to sort out some lockup and sound problems with my wife's PC first, but at least her GF2MX provides the power for the Revelator emitter... | ||
| anonymoose Rating: N/A |
Unfortunately the rise and fall times given in LCD specs only refer to 90% full on to 90% full off and vice versa. Transitions between gray levels are always *much* slower, which means ghosting problems would occur with LCDs and stereo glasses even with very fast refresh rates. By the way, what you would to do with active glasses is remove the front polarizers from the LCD shutters in the glasses - which can be done but risks damaging the LCDs - and make sure the rear polarizers are at 45 degree angles. An alternative is to tape a retarding film from Endmund Scientific on the front of the LCD display (or your glasses for that matter). This detroys the linear polarization of the light coming out of the LCD display (it makes it circulrly polarized) and allows the glasses to work, but it cuts down the brightness by 50%. But why bother - the image is still going to suck because of ghosting. There is a technique that a few companies are working on which employs a blanking field between the image fields - that is, they drive the entire screen to black fast, at higher than normal voltage, to erase the previous image *completely* before the new one forms. This requires operation at 120 Hz to display 60 Hz images, though, because you need to add the extra fields to write the black images. I don't think that it is being used in any commercial products yet. | ||
| Andreas Schulz Rating: N/A |
OK, been there, done that, no cigar ;-) To start with the good news, it basically _does_ work. At my 15"'s native resolution of 1024x768, it allows refresh rates between 60-75Hz. Apparently it faithfully samples and renders the incoming (analog) video signal all over this range. Both (L/R) frames are visible superposed on the screen without glasses; down to 60Hz, the frame alternation becomes noticable. With glasses (old Wicked3D with ELSA emitter, which happen to be perfectly aligned with the monitor's polarization, so there is no loss in brightness when wearing the glasses), at 75Hz flicker is present, but acceptable. Going down to 60Hz, flicker becomes a pain (as should be suspected, at least as long as you haven't watched stereo on TV only up to now)... Talking about pain, we're now coming to ghosting - and that's where the good news finally ends. Ghosting is very strong, even at 60Hz (at least for the NVidia stereo test app, which has quite dark background), and gets even worse when going up to 75Hz. Not much of a surprise, again. Though my discount TFT monitor came without detailed technical specs, they quite sure won't be better than Sharp's current production line. Sharp's data sheets state typical response times of 5ms for black-white and 20ms for white-black transition. Considering that at 60Hz, the duration of a frame is just 16ms, there's not really sufficient time for bright structures to turn into dark background before the next frame starts, resulting in very strong ghosting. All in all, I'd say that TFT's need significant improvements in response times (especially decay time) before combination with shutter glasses becomes reasonable. @moose: Having a degree in physics and some electronics experience (which doesn't make me a LCD expert, though, so I may be wrong), some of your statements sound a little confusing. For response times, I would consider a full black-white (resp. vice versa) transition to be the worst case; everything less (like e.g. 40% gray to 60% gray) would require less re-orientation of the LC's and less capacitive charge change (in case that counts) and thus a) should be faster b) contributes less to ghosting anyway Note that it's just by definition that response time is the time between 10% and 90% output signal level, which is easier to determine; the input transition is of course full 0%-100%. Removing the front polarizer from shutter LCD panels I would consider as a quite ambitious DIY project, and not really necessary as long as you either - can keep the shutter's front polarizer aligned with the TFT's output (which your DIY mod will have to achieve with the shutter's back polarizer anyway) or - can keep the shutter's polarizer at 45 deg rotation w.r.t. the display's (which, to my previous findings, seems to be the default for most shutter glasses and upper-class TFT monitors) and accept approx. 50% loss in intensity. A circular polarizer isn't really necessary in this case. [proofreading reduced due to extensive length, so don't complain about typos ;-)] | ||
| Andreas Schulz Rating: N/A |
apology to moose : W.r.t. greyscale response time problems, I just learned that they _do_ exist, see e.g. this Mitsubishi paper | ||
| nickyj Rating: N/A |
wouldn't LCD manufacturers think to do that as the LCD evolves? It can't truly be a gaming LCD unless they get rid of the ghosting, which would be apparent to the hard core gamer even without stereo. | ||
| Anonymous Rating: N/A |
Thanks for your site! | ||
| Anonymous Rating: N/A |
SarahBell ( ) wrote: |
