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Projector Resolution

486 Views 8 Replies 6 Participants Last post by  hhelmut
I am confused about resolution of projector.

I heard some say that it is better to buy XGA for more pixil resolution. Some say that for DVD that is not need as SVGA is good enough. Also some tell me that for XGA, it will requires expensive line doubler to pay 480p signal from DVD.

So at the end, what is the truth? Or I totally mixed up the issue?

Your advice is most appreciated!
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The resolutions of a projector follow basically the same characteristics as your computer monitor. XGA supports 1024x768 while SVGA supports 800 x 600. Obviously, XGA has smaller pixels, but more of them.

Some people suggest that since the resolution of the image stored on the DVD is less than either of XGA or SVGA, that there is no value in paying for the higher resolution. I don't agree with that, since I would rather see 4 smaller pixels than 1 large pixel, even if the information is the same. Individual pixels become much less visible with XGA. The real concern here, is the fill-factor, which is the ratio of actual lighted pixel VS. the dark space between the pixels. Theoretically, the SVGA panel could have less total dark space since there are less total pixels.

As far as the line doubler, an XGA display does not neccessarily require anything special. As long as the projector can handle 480p, it will directly handle the output of a standard progressive DVD player.

Be careful when reading projector specifications. Be sure to differentiate between INPUT signal capabilities, and actual OUTPUT panel resolutions. For instance, just because it says it is HDTV-compatible(1080i), doesn't guarantee that there is a place for every pixel in the actual displayed image.
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All that you said is true (and false). It really depends more on the Projector then anything else. The Projector needs to take the image coming in, and map it to the size and type it can display (XGA / SVGA most common). How this mapping is done will affect the picture. This (mapping circuitry) is one place where the projector manufacturers can cut cost and it won't show in the specs. That is the reason that people use a line doublers or other devices to bring the image to native rate (1 to 1 mapping, so you bypass the internal circuitry) Since there is a bigger difference between 480p and XGA, the internal circuits play a bigger role, and therefore (chances are) can benefit more from an external doubler (but necessity would depend on how finicky you are and the quality of the internal circuitry).

Also, don't mistaken native resolution with maximum resolution. Native resolution=what is the resolution you see, Maximum resolution = what you can input in the projector (i.e. you get the opposite of line doubling for all resolutions between Native and Maximum)
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Yeah, but I used smaller words;)

Although AnthonyP did make a good point about the internals (electronics, scalers) having to play a bigger part in an XGA projector, simply because there is a bigger difference between the input signal and the output device. Consequently, an XGA projector with a poor internal scaler, may indeed benefit more from an external scaler, than would an SVGA. And, of course, that point becomes even more important as the actual panel resolution approaches SXGA or higher.

My original comments were aimed more at the apparent misinformation to the new member that an XGA projector required an external scaler for 480p. Clearly, that is not the case.
mostly the same stuff but then again we were answering the same question :)

I just think that there is no clear answer to what format will give the best image, and what is not said about the projector (what can be seen with the eyes) is MUCH more important then the specs written on a piece of paper. That was the main point I wanted to make (it might be easy to generalize and say XGA will give a better image because.... or SVGA will give a better image because....) but I think when all is said and done there is no absolute answer (which was what the original poster was asking). And since I was adding that I go why not confirm what Jim had said


All that you said is true (and false).
was meant to the original posters question and not Jim's response
@ AlienAlien

it isn´not so complicated as it seems.

Let us get to the basisc of resolution. All the other things like LCD or DLP, contrastratio a.s.o will another point.

I will not going into deep technical details, I try give you a simmple answer

The only think you have to mention will be the native resoltion of the panel of the pj, the rest will be scaled (using less native resolution than the signal will recommended, you will loss some information)

In the following I give some information, which resoltion will be needed for the different signals

a) 4:3 signal interlaced or progressive just like normal TV ->native resolution of the pj 800x600;

b) 16:9 signal comming from a DVD and will be interlaced or progressive (480i/p) the native resolution of the pj will be 848x480

c) 16:9 signal like DVD in PAL interlaced or progressive (576i/p)

-> the native resolution of the pj should be 1280x720 (WXGA),

d)720p signal given by cable is an progressive Signal -> the native resolution of the pj should be 1280x720 (WXGA)

d) 1080i signal the native resolution is still not avaibel (the panel must be 1280x1080)

When you have a look at thes e panel size, than you can do the following decision

a) panel 800x600 is good enough for 4:3 format all the other formats will be scaled

b) a NTSC Signal in the Format 16:9 will be presented exatly by 848x480

c) PAL ist not common in the States therfore no rec.

d) 720P (which is still the better signal than 1080i because it is progressive)

you have too choose 1280x720, when you will use a XGA-panel with 1024x768 you will loose information

a) 1080 there is still no pannel arround

maybe, this will give you help to your question; In your case you should get a pj which will work with a natitv panel of 848x480 or XGA (1024y768) or if your wallet will give take 1280x720 or an D-Ila with 1280x1024 because this will windowresizing

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As everyone here has stated, an XGA pj with a good internal deinterlacer/scaler will make a great picture without the need for an external box. Look for pj's using the DVDO 504 chip or Faroudja DCDi chip. The Pixelworks chip generally does a good job as well, but not to the level of the 504 or DCDi.

Unfortunately, many pj's don't list the chip in the specs.
@ AlienAlien

Adding to Jim recommodation, the signals given by TY, DVD, VCR are normaly interlaced (not the 720p); Therefore a pj using such an internal deinterlacer/scaler will give your picture from normal TV, VCR or TV a spped up, it will be just night and day;

for the beginning, start at minimum with an 848x480 as native resoltion (but with an built in deinterlacer like piano or LS 100 or similar modells) or get an XGA with an build in deinterlacer/scaler like 753 or similar modells.

Then IMO you hve all option also for the future and wonßt waste to much money for the beginning - BTW it becomes later more and more a very wllet used hobby

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