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I can see the difference when projecting a computer screen (e.g., Windows desktop, start menu, etc) in a 800x600 Vs. 1280x800 resolution for example. But when watching movies is there going to be a difference? It seems you will not lose any part of the picture regardless of resolution. Is this correct?

  • If you cross your eyes while watching the movie, is any information lost? – Michael Feb 27 '15 at 17:15
  • Color rendition can have as much impact to perceived picture quality as spatial resolution. The ability to notice the picture details will depend on the source material, viewing distance and your eye sight. The emphasis on a display's resolution is driven by TV marketing hype. There's always a specification de jour to sell new TVs. Nowadays it's "4K", and previously it has been "480/240/120Hz" (refresh rates), "3D", "LED" and "1080p". – sawdust Feb 27 '15 at 20:03
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Of course it matters. Even at smaller projected sizes, the resolution makes a huge difference.

HD video is between 1 and 2 million pixels, if the projector cannot display all of them, there will be a loss in video quality. Additionally, depending on the distance from the image and the size of the image, you may be actually able to see the pixels on the projection location. A 1280x800 projector will display all the pixels of 720p video. An 800x600 projector will display less than half of them.

At a distance of 20ft, I can easily see the difference between 720p and 1080p on a 50" display, and on a large projection surface (say 150"+), I can see the individual pixels of a 1080p projector. More pixels is better.

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That is correct. The picture will be scaled to fit in a given resolution.

It might not be the same picture though. Like when the movie's resolution is greater than the projector's. It makes sense that detail, or call it resolution, will be lost.

Using a 1280x720 resolution movie as an example, a projector set at 800x600 will have to throw away a lot of information, since it's new job is to display 921,600 pixels (1280•720) with less than half that available to it. The 1280x800 setting can comfortably fit everything in its workspace.

Still though, for projecting movies, the thing that matters is up to you when you're sitting in your seat. If you have a 4:3 screen that can only accommodate 1280x800 by shrinking the image far beyond the size of how 800x600 compensates with the movie, then maybe 800x600 is better.

But if you're talking about details, and not cropping, it matters a lot.

  • Does this mean that a 720p movie will not lose picture quality in a 640x480 projector? And that it will only lose quality when played in a 1920x1080 projector? – IMB Feb 27 '15 at 8:10
  • @IMB No, sorry... I have to think of a better way to explain it. They'll both lose quality in that case, your media player probably offers you various resizers to minimize this. As a general tip, if you find resizers don't use "nearest neighbor" and project at the higher resolution. If it's hard to read things, look for DPI/scaling settings at the OS level. – Louis Feb 27 '15 at 8:11
  • @IMB But if you're thinking about this, think about how 1280x800 won't lose quality in that case, but 1920x1080 will. Once you start resizing, up or down, the quality drops. At 1280x800 it actually doesn't resize at all. So you can see why there's no simple answer... – Louis Feb 27 '15 at 8:22
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The most basic concept in resolution is that the further you are away from the projector, the less the pixel density. Let's say that your projector lense is 4" in diameter. If you focus on a screen that's 1 mile away, guess what you will see? If the number of lumins isn't beyond all reason, you won't see anything and your pixel density on the huge screen will be virtually less than 1 pixel give or take. Basic physics teaches about focal points and distance from source. I assume that my home projector has a much better pixel density than what I see at a movie theatre for 1 reason. The typical distance from the projector in the theatre to its screen is over 70'. In my home theatre, we sit about 15'-16' away from the screen.

  • 1
    You're right that there's a relationship between size and distance (and brightness). But this doesn't really answer what was asked in the question. – fixer1234 Mar 5 '17 at 2:51
  • Please read the question again carefully. Your answer does not answer the original question. – DavidPostill Mar 5 '17 at 11:25

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