Projector Connection & Screen Placement

[Doug S]

DVI,Component,Composite, is that the order from best to worst?.I was told that unless you were watching in HD that DVI doesn't make that much difference.Then component is the way to go? Well on the 4805 for instance you can go with component hookup but running it from my PC I only have one component jack so then I can go component to VGA? I was told that wouldn't work either I mean with VGA being from PC end. So then is VGA to VGA the best way to go? better than S-video I'm told. I'm confused Any suggestions or thoughts on this guys?


Also has anyone ever used a screen over a picture window?...Kinda killing two birds with one stone so to speak. Would that be a good idea or not? Just thinking about these things ahead of time. Thought I would run them by you guys for imput......thanks, Doug

[JonMarsh]

Best to worst depends a bit on the characteristics and idiosyncrasies of both your projector and source unit.

From an absolute signal bandwith viewpoint, technically RGBHV may have the widest bandwith, regarding color signals, and since it's analog, can represent a wider range of values- there are components with 10bit and 12bit video DAC's. Some diplays still digitize an RGB signal (well, obvioiusly, most digital displays do), so the resultant quality is dependent on the internal A/D.

DVI byapsses this, and gives you the DVI digital signal at the nominal bit depth used- nominally 8 bit, though component can have 10 bit with reduced chroma bit depth.

BUT, there's a difference in nominal DVI levels between CE gear and computers, and not everyone keeps that straight even in one category. As a result, many early DVI components have issues with black crush (not transmitting the correct levels for very low level signals- resulting in loss of detail) (Samsung comes to mind, for example), or white crush- using the wrong reference level for 100 IRE, and losing shading control in the brightest whites (Zenith DVB318 is an example there).

For many of the Samsung and Zenith models you can actually get the highest fidelity signal overall through the component outputs into a good projector- especially a CRT projector which doesn't digitize the signal.

Are you getting a bit of a headache from all this? Believe me, I do, too, and I'm a double E.

Then, there's the matter of tradeoffs between luminance bandwidth (black and white), and color bandwitdth (chroma).

Composite has the worst capability in this regard, because of how the signal is stored. While the luminance bandwidth of a composite signal can extend up to 3.7 to 4 MHz (about 400 TVL), the color bandwith is effectively only about 40 - 50 lines of resultion (imagine trying to reproduce alternating lines of cyan and pink at the same luminosity- this is where composite really falls down.

S-Video transmits the chroma composite signal separately, instead of mixed in with the luminance, and chroma bandwith roughly doubles- 100-120 TVL typical.


Component connections, with two seperate color difference signals, improve things futher, but still cut the chorma bandiwth by half compared with the luminance. Still, with good source, on a good display, the results can be very good. A lot still depends on the A/D in the projector, if present, and subsequent processing.

If you're running from your PC, you should set it up for native resolution on the projector, and use RGBHV (VGA) mode. Don't forget to calibrate brightness and contrast using a good test disk, like AVIA or Video Essentials. There may be separate brightness/contrast contols on the overlay for DVD output on your PC; set those to default and adjust the display first.

Regrettably, every output device, whether PC, DVD player, or HDTV tuner seems to have slightly different output voltages, and so when using analog connections into an A/D, you want to be sure they're setup right.

This is where DVI, when it actually works, is a good thing, because there should be any such issues assuring that the little bits don't get lost.

Oh, I didn't mention those units that use DVI inputs, convert it to analog, then re-digitize? They're a lot more common than you'd think, due to the way companies have to "patch togeher" different processing chip sets, like scalers, etc, inside a projector.

~Jon