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Hi all! While watching movies with medium to fast pans, my VT-540 has a lot of "motion blurring". That is to say that while panning, the picture gets blurry and hard to view but then becomes quite clear once the pan has completed. I'm using my HTPC as the source for this projector. So, my questions are:


1) Is this an inherent problem with this model, or the nature of LCD projectors?


2) Are other technologies susceptible to this?


3) Can I do anything to improve or eliminate this blurring?


Thanks for any information you can provide!!!


Jeff
 

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I was at the theatre yesterday. I did see motion blur on 35mm film. So why should all DVD transfers be motion blur free. Don't ask me. Check the material first. Maybe it is not the PJ atfterall.
 

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Well, in the past, LCDs have been known to have slow decays, so it could be the projector, but the quickest thing to try is to pause some action frames and see how much different it looks. One can get a general idea of the persistence in the particular LCD unit by moving the mouse around quickly.


Film often has motion blur as well.
 

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Blurring is a characteristic of some LCDs when the LC material can't change polarization states rapidly enough. Often panels designed for graphics, not motion video, don't switch quickly enough. But MPEG-2 encoding/decoding can create similar problems, too. And, as noted, it occurs from other sources. It's even a problem with retinal/optic nerves when neurons can't transmit signals rapidly enough. -- John
 

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35mm will have some motion blur due to the length of the exposure, but also keep in mind it's 24fps, which sucks with panning. 24fps is barely enough to trick the mind into thinking the images displayed are moving without flicker. Once you start panning, you begin to see flickering.


You might want to make sure your scaler is set to 72hz refresh rate (24fps x 3), which should eliminate any problems the projector should introduce.
 

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I don't know how fast (or slow) VT540 panel response time is but it seems quite fast. If anyone has these numbers, please post.


Quick test by using PC is to move window around screen. I have tested and it seems pretty good. Some blurring can be seen but I have seen much worse. One thing about refresh rates is that 60Hz is the only one that works with VT540. All other refresh rates causes tearing.
 

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Pj LCD panels (and DLP panels, and LCOS panels) all have an inherent refresh rate of 60Hz.


Some newer LCD monitors have refresh rates of 75Hz and 85Hz. Once this refinement finds it's way into pj's, things should be a bit clearer.
 

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Quote:
Originally posted by Jim Scarbrough
Pj LCD panels (and DLP panels, and LCOS panels) all have an inherent refresh rate of 60Hz.
I didn't mean that refresh rate. It is true that most LCD/DLP projectors convert everything to 60Hz but there is also panel refresh rate.


I've seen some manufacturers specs claiming that LCD panel refresh rate is something like 25 to 50 ms typically. (If panel refresh rate is something like 50ms there will be a lot of smearing during camera pannings.) That's the number I am looking for here.
 

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It is a combination of problems:


1. 24 frames per second isn't enough for good action. It is a bare minimum. But to shoot at that rate, the camera operator uses a rather long exposure time/aperture. This causes some blurring. If the exposure time is left real short, like Saving Private Ryan, the images are very crisp but the image becomes "jerky" to watch.


2. As already mentioned, the response time of LCD's is hardly finite and this isn't a completely bad thing (helps hiding static type noise). Response time for LCD projectors is rarely mentioned but the numbers I remember were in the 25ms to 35ms range. This means that LCD projectors start to struggle with 60 frames per second material.


If I were you I would try to play a video game (or Saving Private Ryan) on your projector to see if you are still getting the blurring.


-Mr. Wigggles
 
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