There are two versions of this reply - Basic and Advanced. I offer both so that no matter where you are on the 'Techie-O-Meter', you can get direction on this often misunderstood subject:
First, the comments and question raised by a reader of mine, Scott Steffan:
My only comment on scan converters is that you will always lose resolution quality in the conversion from computer-RGB to S-video or composite video. At least this is my experience and I have only spent 200.00 on a scan converter.
Are there very good scan converters that you would have to split hairs to see the resolution quality difference when it makes it to screen?
- Scott Steffan
There is always a loss when down-converting (Scan Converting) from computer to video. However, a $200 scan converter is going to degrade the image severely. So, yes, there are very good scan converters that are offer only a slight loss of quality from the original computer image.
The RGB (usually HD-15 pin serial connection) is based upon a computer resolution input. In other words, you hook up the output of the computer to a box (Distribution Amplifier - like a P2/DA2) so that one output continues to the computers' monitor and the other runs out to the projector.
The quality of this image is based upon the output resolution of the computer. It is not uncommon to have 640 x 480 or 800 x 600 or even 1024x768 as computer outputs. The higher these numbers, the better the resolution (nice and crisp, not blocky).
It is best to find out what the "native resolution" of the projector is (usually 800 x 600 or 1024 x 768), and send the exact same output resolution from the computer to the projector. This will yield the best looking-image for that projector.
The SCAN CONVERTER comes in when you want to run a video signal to the projector (not RGB HD-15 pin). Why do this?
Let's assume you have a VCR, a DVD player and a computer that all need to be projected. To make "seamless" (no glitches, no blue or black screens in between) transitions between the DVD, VCR and computer, we need to 'agree' on a standard type of signal.
Since Computer signals are completely different from video signals, we need to make the computer common (scan convert) bringing it down to video. Now we can use a video mixer (switcher) to dissolve, cut, wipe and key in video - because all three sources (in our example) are now video.
In the above scenario, we lost resolution coming down from computer to video. But what if resolution is paramount? Glad you asked...