DLP + 3D Vision = no Ghosting, but why?

[mcx]

Can somebody answer this question?

I'm thinking about the option to buy one of these new 3d DLP projectors for 2 reasons: 1. no ghosting and 2. bigger screen = more cinematic 3d feeling

Currently I'm using the Sony GDM-FW900 with my 3d vision where the 3d effect is good but there is sometimes (depending on some footages) ghosting noticeable...


thx
MCX

[Likay]

Since it seems that dlp's never causes ghosting with 3d-vision it should mean that the sync between glasses and displaysignal is good but some displays lacks ability to shift image fast enough, hence the ghosting. It's a cautious assumtion from my side though.

[Gae43]

That's an interesting observation which I have noticed with my system too. I get zero ghosting on my DLP Infocus X1 but when viewed on my CRT monitor, the same material quite often has ghosting.

Gae43

[vrekks]

Because it wobbulates silly...

But seriously, unlike LCD pixels which have to change from one color to another (as can be seen by the "response time" specification) a DMD (digital micromirror device) is constantly changing many hundreds times per second (something in the ballpark of 60Hz * 6 color wheel segments = 360 refreshes of the tiny mirrors on a DMD per second). Another factor to consider is that since wobbulation is used, this number must be doubled to provide both halves of the screen's pixels (or the left and right eye views of a 3d video). So the reason why DLP sets do not ghost is because it is inherent to the nature of the technology to be extremely precise. If the TV was miscalibrated to cause as little as 1/720 second delay then the house of cards would come tumbing down. I am just drawing off of my knowledge of DLP which could have changed so you should just wiki it.

[Likay]

The liquid crystals themselves has no problems switching fast (shutterglasses uses liquid crystals..). The problem with lcd is that the signal needs to be read into a memory and then "shipped" to the display. This "shipping" can only be done with a certain bandwidth limited by the lcd-monitors electronics. If manufacturers improve the electronics of an lcd it should be capable of a good image in 3d.

A dlp or crt monitor usually draws the image "as is" in the signal without delay and that's why they works decent with shutters. Crt's have their phosphoric decay which cause some ghosting.

[vrekks]

Excellent point about lcds having to process the signal before displaying but shutter glasses are a different beast than a color lcd when it comes to response time in regards to processing and displaying images because of shutter glasses' binary nature and single pixel display.

"LCD technology is not usually rated by frames per second but rather the time it takes to transition from darkness to brightness and back to darkness, in milliseconds. In order to achieve an equivalent minimum refresh rate of 120 Hz, an LCD must be able to transition at a speed of not more than 8.33 ms." -wikipedia lcd shutter glasses

I'm not sure you would be able to find any lcd that can process and display a specific color for 2,073,600 pixels in 8.33 ms besides ones specifically designed for S3d that would be prohibitively expensive.

"Today, many DLP projectors being built for the home theater market incorporate a six-segment color wheel which has two sequences of red, green, and blue. This wheel still spins at 120Hz or 7200 RPM, but because the red, green, and blue is refreshed twice in every rotation rather than once, the industry refers to this as a 4x rotation speed. This further doubling of the refresh rate has again reduced the number of people who can detect them [rainbows]." -projector central

So IMO due to the seperate nature of the image producing agent (the dmd and the lamp) and the color providing agent (the color wheel and the lamp) as well as their sychronicity, DLP is better at producing a new image faster than color lcd, ie better response time, thus leading to less ghosting. By no means do I disagree that monochrome lcd is slower because if it was my 3d vision glasses would be ghosting rather than the DLP display.

In response to the more cinematic feel of a large screen projector I would reconsider this if you plan on playing competitive online games because of having to shift your eyes left, right, up and down constantly rather than let your view settle over the entire screen at once. You can sit further to allow for less eye movement but then what is the point of the gigantic screen unless you have a bunch of friends over watching as well. My maximum comfortable view without too much eye movement is about 65-70 inches at about 6-7 feet. A 60 inch at 7 feet is very comfortable for me.