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Thread: are video projectors replacing laser projectors for graphics?

  1. #101
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    Not to mention the mutlicolored rainbow effect when shifting view. I don't know how people can stand that. Talk about triggering epileptic seizures. If I ever bought a projector, it sure as hell wouldn't be DLP. I would buy LCD only.
    I chose the projector for its ability to produce the highest contrast (I found the DLPs were significantly better here) along with the most light output. The blinking rainbow effect is visible to me (and annoying) only when I am looking at the projector and invisible when I am looking at the screen.

    The projector I am using is a Acer P7500. I got it a couple of years ago at New Egg for around $1,600.
    The reason the graphic should not change brightness when going from a low scan rate of say 20K to say 60 K is that the only difference is the number of times/second that the entire image is over written. The same number of photons/second strike the screen.

    m0f,
    All very good points.

    As a tangent, I want to say I repainted my large projection screen this week. The area is too large to make a commercial screen affordable and when I bought the projector I constructed this screen and after perusing the forums (especially AVS) I had used a DIY mix to paint this screen called "magic mud". This paint claims to have gain of one. I was afraid of the high gain paints because I did not want to have to wear the projector as a hat to see an even projection without hot spots. The screen worked well for video (lots of HS kids, party/movies) and for lasers as well. After accumulating a few dings I decided to repaint and went with a particular commercial screen paint ( I won't hawk it here) with a claimed gain of 3.6 and...holly cow! It looks like a 1920 x 1080 monitor on steroids! It is now larger than our local theater and at least as bright and I actually decided to turn down the lasers (I never thought I'd say that). The dreaded hot spots did not appear and the viewing angle is still much wider than the room will accommodate. I suspect that an even high gain might be possible and this could improve the performance of video projections when the surface is dedicated for that purpose.

  2. #102
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    I actually do this a lot. When you adjust the software parameters on Beyond to optimize the projector such as min/max points and blanking. The most important adjustment is the trade off for speed. The faster, the less blinking, but the more rounding of corners and artifacts. I do not notice a change in brightness as I slide up and down on the scan rate.

    I have to stand by my example. I believe it is fair, but it is intentionally the most extreme limit of the two systems that I use to illustrate that the two systems are fundamentally different. As the projection area (total illuminated fraction of the screen increases) there will be a crossing point where the video projector will actually equal the brightness of the laser. In my example that will occur @ around 40%. Beyond this point the video will appear brighter.

    Have you seen large raster images generated by a laser? They are pretty dim and do not compete with the video projector. The graphics generated by a laser are basically line drawings that match well with the scanned point source of the laser. Video projections are basically area filling images that take advantage of the video's re-imaging of the DLP chip
    Last edited by planters; 08-23-2014 at 13:25.

  3. #103
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    Yep clearly LCD/DLP is the better choice compared to scanners, why is this even a question? Plus you have infinite possibilities with DLP/LCD, laser is so last century!

  4. #104
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    Quote Originally Posted by solidude View Post
    The point is, the projected graphic is less bright, or dimmer than a single point and this is why i think it's not fair to compare the full brightness of that single laser beam point with the brightness of one pixel from a video projector, like I said.
    And I still don't understand why we are comparing a single pixel only with a laser point either. That will look shit even leaving the whole brightness thing aside.
    Because if you draw a thin line such as an outline animation such as you would a laser, then the video projector in projecting that will only have the number of pixels needed to light up the line lit, and thus it will only be using a very small percentage of it's overall brightness.

    Also, you can't just discard coherence. I use Light Converse which is supposed to be one of the most accurate lighting simulation programs on the market and is aimed mostly at non coherent lighting although it does lasers as well.

    Now above I believe you mentioned somewhere above about a video projector at 7,000 lumens have the same number of lumens as a laser.

    What I can tell you is that in order for me to get a realistic brightness out of LC for my 3W laser in simulation, I set it to around 250,000 lumens.

    That should give you some measure of the effects of coherent vs non coherent light sources.

  5. #105
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    Solitude,
    The scans really don't get brighter and they shouldn't. You seem to suggest that it's a little like a strobe light-all the light concentrated into a single scan. It doesn't work that way. A 1 watt beam produces gobs of photons, but let's just say it is 1000 photons per second for the sake of this example. The drawing rate is not once/second say its 10times/second on slow then its 100 photons/ scan times 10 scans = 1000 photons. Now draw the same exact pattern at 50 scans/second. You place 20 photons with each scan and with 50 scans you have placed the same 1000 photons on the same pattern. No more or less photons are deposited in either example. The eye responds to the average photons in any given period of time when the speed is sufficient to produce a useable image. Now, if you waited a minute and drew the pattern with 60,000 photons in one shocking projection then yes this would appear brighter as a strobe light seems brighter, but these laser projectors don't operate so slowly that that effect can be generated. One scan per second is way out of the normal range and would look terrible, but maybe then it might look brighter? Not to the point, however.

  6. #106
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    Solitude,
    @planters: I dont know how theres even a need to argue this. You're saying if the scanner projects 30000 points per second, each point will be as bright as a single beam point ?

    Of course not,you miss my point entirely, probably my fault for not explaining this clearly. No matter how fast you draw THE SAME CIRCLE with the same laser it will not get any brighter or dimmer. There is no issue of my believing you or not. Of course, a point will be brighter than a circle when drawn by a laser, but that's comparing two completely different projections just like a projection on a screen at 1M is brighter than a huge projection at 10M.

    Now, I think you need to get a hold of a laser projector and a video projector and actually run them with a variety of output. Run beams and graphics, in a dark room with haze and without haze. The comparison is more complex than you might think. The issue with a focal plain vs colimated light that m0f brought up is significant. I mean this, you need to run these experiments yourself.

  7. #107
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    Quote Originally Posted by planters View Post
    I mean this, you need to run these experiments yourself.
    THANK YOU!!! As I had stated earlier. We have all answered his questions to a point of inane redundancy. I tip my hat to you, Eric. Your patience goes miles beyond mine. Hell, it goes A.U.s beyond mine! Thanks for the information though.
    If you're the smartest person in the room, then you're in the wrong room.

  8. #108
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    Quote Originally Posted by solidude View Post
    I already said, I won't be just converting the vector frames to 1-pixel wide raster lines in a raster frame. That would be retarded and no way would emulate the laser feel. I already explained what I'd do, which Beyond does partially itself.
    It doesn't need to be just 1 pixel. We've already explained that in a video projector, the projector only lights the pixels in use.

    If you have a video projector with HD resolution, you have 2,100 pixels (2.1 MP).

    Each pixel is lit individually either by LED or by mirror (DLP).

    So if you draw a character made up of an outline graphic like a typical laser projector then if it's 4 pixels wide, you're using 4 pixels x the length of the circumference of the line. So, if for the sake of argument the line is 80 pixels in length, you're using / have lit 4 deep x 80 pixels long = 320 pixels.

    Given that full brightness is achieved at 2,100 pixels you have 320/2100 = 15% brightness.

    So far as LC Converse is concerned, I'm reporting the simulation not the real world, although generally it's accepted as very accurate in it's simulation. I put the difference down to coherence.

    In relation to BB and 500mw laser comment, that was made in reference to beams not graphics and you're losing less visible photons over short distance with beams because the haze means that everything that leaves the aperture is reflecting back to the viewer off the haze whereas with graphics lost photons aren't seen, only the ones that strike the projection surface as a part of the drawn figure are what are actually perceived. I believe there's comment elsewhere as well that Simulated Laser doesn't work well at distance as too many photons are lost resulting in poor brightness and large divergence at distance.

    My own experience with laser is that 3W off a white wall or screen with graphics from 10 feet or so away, can be so bright as to be too painful to watch. I've never had that experience with video projectors even when at the front of the cinema with projectors of huge proportions and brightness.

  9. #109
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    " 15 characters"
    Last edited by Laser Wizardry; 11-13-2015 at 12:09.

  10. #110
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    Quote Originally Posted by solidude View Post
    Even better that it was made in reference to beams, most people here dismiss video projectors for beam shows right off the bat. You're right with the haze the photons are "reflecting" off the haze particles to the viewer, but this does mean there's enough photons coming out from the video projector to get reflected like that and appear as bright as if you were looking at a 500 mW projector beam and not have the beam fade away after few meters. Test was done at a distance one of the main people of this industry find good enough.
    ..and he also comments that they're trying to find ways around the poor brightness with narrow beams (caused by the fact that only a fraction of the brightness is used when you project a small object).

    Look at this video - you can clearly see that close up sheets etc are fine but "pencil" style beams are of poor brightness:

    30 secs is the 1st instance where the individual beams are dim

    The larger effects such as fans etc are reasonable.


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