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DVI to VGA - noticeable quality loss?

Tags:
  • Tuner Cards
  • DVI
  • LCD Monitor
  • VGA
  • Graphics
Last response: in Graphics Cards
January 19, 2010 6:00:26 PM

Hi there,

I can't seem to find a solid answer to this question.

Firstloy, I have a DVI LCD monitor that looks awesome when hooked up in DVI mode. When hooked up with a VGA adapater I can instantly see the difference (mostly blurry text).

However, if I were to take DVI to VGA adapter (DVI side jacked into my video card - VGA jacked into the monitor) would it be the same as running a plain VGA cable, or would I keep the DVI sharp quality.

Hope this makes sense.

More about : dvi vga noticeable quality loss

January 19, 2010 6:13:35 PM

As far as I understand it, DVI jacks actually have dedicated pins that provide analog VGA-style signals out them. When connecting an analog monitor through a DVI-VGA adapter, you will be using the analog signal, and getting the analog quality. Keep in mind some DVI ports do not have these pins and you will simply not get any video. Hope this helps :) 
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January 19, 2010 6:16:47 PM

nanert said:
As far as I understand it, DVI jacks actually have dedicated pins that provide analog VGA-style signals out them. When connecting an analog monitor through a DVI-VGA adapter, you will be using the analog signal, and getting the analog quality. Keep in mind some DVI ports do not have these pins and you will simply not get any video. Hope this helps :) 


I'm testing it now and to be honest, I can't tell the difference between this and straight up DVI to DVI. What you're talking about is DVI-I and yes, my video card port supports that.

Remember that this monitor has both a VGA and DVI ports.
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January 19, 2010 6:23:14 PM

Just found an answer that I think solves this.

"Yes. You will see no difference in quality.

Your video card deals in digital signals.
The old CRT VGA monitors required analog signals just as the old CRT TVs did. These signals were directly used to drive the "color guns" on the CRT.

So video cards have (or had) to convert these digital data to analog before sending them to the CRT monitor through the VGA connector. This is what the RAMDACS (or just DACS, for short) on your video card are for.
The DVI connector on your video card has both analog pins from the dacs and digital pins which skip the dacs.
Your DVI to VGA adapter just uses the analog pins and wires them to a 15-pin D-sub connector, AKA "VGA connector".

Now while it's TECHNICALLY true that DAC conversions are prone to error, the error rate is so low and fleeting that it is just flat out impossible for the human eye to detect them when compared to pure digital.

So to reiterate, yes, you will get every bit as good quality with your adapter as you will with the raw digital."

So according to that, DVI to DVI is the same as DVI to VGA. However VGA to VGA is still noticeably different.

Any experts on here agree?
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January 19, 2010 6:39:02 PM

Ive heard that many people can tell a difference between DVI and VGA but only at the higher resolutions like 1920x1080 or 2550x1600. only a handfull say they can see it at 1650x1050.
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January 19, 2010 8:57:43 PM

There is very little to difference to none with respect to quality of display. That is assuming all the cabling and connectors are working well.

If the DVI works that the recommended interface. Use DVI.

DVI(being digital) has better immunity to noise than the analog VGA cable. To site you an example VGA extension cable normally results to ghosting on CRTs.
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January 19, 2010 9:41:06 PM

90% of the time when you have a blurry signal over vga to an LCD it's because you have your refresh rate set incorrectly.

I'm guessing you have it set to 75hz. Try setting it to 60hz.

Basically what's happening is your lcd can't really use the 75hz signal so it's down grading it to 60hz and in the process it gets blurry. If it's 60hz to begin with it'll stay sharper.
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January 19, 2010 10:57:33 PM

Generally text has a small bit of ghosting on VGA at higher screen resolutions. It should not be too bad, but it can be seen. Its not notices on images and stuff, but on pages of text, i can see it for sure.
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