| Author | Message | ||
     Anonymous Rating: N/A |
I recieved a sample SilverFabric screen yesterday and started my first polarize 3D experiment. I have only one DLP projector. I put plastic looking linear square polarized filter just at the front of projector and looked at the silver screen. I was expecting to see nothing when I shut one of my eyes. Of course there was considereble difference btw right and left eye images but I could still see some pale images on the screen. I wonder if this is usual situation with passive stereo or using better screen material or polarizer filters can reduce or completely prevent unwanted ghosting in passive stereo? | ||
| M.H. Rating: N/A |
What you see is absolutely normal ... You can use filters with higer polarization, but they will absorb more light. When you will run real polarized stereo projection you will see that the ghosting is close to zero ... My company is renting screens from SilverFactory materials and there was only positive reaction from clients ... | ||
| Anonymous Rating: N/A |
Then, what is real polarized stereo projection? Can we do it at home? | ||
| Hd Rating: N/A |
@anonymous Of course you can do it at home, but need 2 projectors with a special polarization filter, a speacial non-polarization screen and passive eyeglasses matching your 2 projector filters for left and right eye;) just do a search on goolge if you want to know more about this technique.. | ||
| Alatar Rating: N/A |
I concur. In practice a SilverFabric screen with good polarizers on both the projector and the glasses has almost no ghosting. Sorry if you just omitted this from your post because it was obvious, but you didn't mention that you had a polarizer in front of your eye as well. I trust that you do realize that both are neccessary (and another two for the other eye)? | ||
| Jim Rating: N/A |
Hello all. I think this is an important thread to address, because I was also quite perturbed to find incomplete filtering by the polarizers as mentioned in the first message. I actually believe that it is due to failure of maintenance of polarization by the silver screen. Evidence to this is that the filters I have will 100% extinguish all light if crossed by 90 degrees, so I don't think that they "leak" light. This said, I also agree that the ghosting is surprisingly minimal (or non-existant) given that polarization does not completely eliminate the "bleedthrough" that was described in the original post message. It's the ratio of the two eyes that's the significant issue (basically a form of contrast ratio). When the opposite polarized light is projected onto the dimmed one, the bleedthrough becomes rather insignificant. (it's like beaming a 1000 lumen projector on top of an image of a 200 lumen projector, you don't see squat of the weak projection). I would like to dispel a couple of myths that I came across while I was trying to figure out what equipment to buy (this will have a bearing on the original post at the end). 1. LCD works fine for me (you don't have to go DLP). 2. You don't need 2 of the same projector (mine are different brands completely). 3. You don't need extremely bright projectors (1000 lumens works well, and I am projecting a 10' diagonal) Sure, the brightness is halved after polarization, but then you've got two projectors beaming on the same spot, so you're back to where you started. Anyway, turn out the lights...better experience. 4. You don't need the images exactly overlapped (I have a ceiling and ground mount for my two, and they even have opposite keystoning, which I don't correct because digitally correcting keystoning means losing resolution). With respect to the original thread, the one problem that I experienced with ghosting is that my projectors are 1200 lumens and 2000 lumens. The 2000 lumen Sanyo has enough "bleedthrough" to the other eye that it rivals the other projector's lumens. So, ghosting can be a problem if one projector is perhaps more than 50% greater brightness than the other. To solve this, I placed two polarized filters in front of the Sanyo lens. Oriented in the same direction they do not cause any noticeable dimming of the light. However, rotating each filter in opposite directions will slowly filter more and more light (go to 90 degrees and you filter all of the light, so don't do that). This way, the bleedthrough can be slowly "turned down" until ghosting is no longer an issue. You need to rotate both filters opposite directions because LCDs have inherent polarization of the different colors, and you want to filter these colors equally. If anyone has questions about my system, I can explain my materials. I spent $800 on each of two XGA projectors (overkill), $200 on the 100" diagonal Dalite silver screen, and $30 on filters (you can get the filters cheaper). I got this thing up and running in about 15 minutes after I received the silver screen. Of course glitches occur all of the time still. jim.wilson@knology.net |
