Date: Wed, 2 May 2007 02:29:07 -0700 From: "Ted Mittelstaedt" <tedm@toybox.placo.com> To: "Victor Engmark" <victor.engmark@gmail.com> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: RE: How to find HorizSync / VertRefresh rates? Message-ID: <BMEDLGAENEKCJFGODFOCCEALCAAA.tedm@toybox.placo.com> In-Reply-To: <7d4f41f50705020205q24d452efpde5e4e1867d99864@mail.gmail.com>
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> -----Original Message----- > From: owner-freebsd-questions@freebsd.org > [mailto:owner-freebsd-questions@freebsd.org]On Behalf Of Victor Engmark > Sent: Wednesday, May 02, 2007 2:06 AM > To: Ted Mittelstaedt > Cc: FreeBSD Questions > Subject: Re: How to find HorizSync / VertRefresh rates? > > > On 5/2/07, Ted Mittelstaedt <tedm@toybox.placo.com> wrote: > > > > I feel the need to remind folks that the concept of refresh rates is > > completely meaningless with LCD panels. Flatpanels do not have a single > > scan gun that draws lines at a specific time and rate of speed across a > > phosphor. > > > Well, the rates are both related to the video card, not the > display. I'm not > sure how the card feeds the image to an LCD display, but I guess > that would > depend on the enforced horizontal sync and vertical refresh rates. If your using a VGA connection then yes it does depend on the refresh rates. But the refresh rate has no meaning after the signal is processed by the LCD panel's computer. > In any > case, it's useful to have these rates if I should ever have the need to > attach the card to an external CRT display. > > The computer in the LCD panel takes the video input at a range of refresh > > rates, and converts it to a bitmapped image that is fed to the display > > crystals. You can use whatever horizontal and vertical refresh rates > > you want, as long as they are in the table that the LCD panel's computer > > can decode, the resulting output is the same. > > > Even though LCD displays don't flicker, it's useful to set the refresh as > high as the panel is able to display, to get smooth transitions. > Try different rates, I think you will find that once you get above 70 Hz you won't be able to see any difference. > I also will remind people that the pixel counts as resolution on > flatpanels > > also have no meaning. A flat panel has a fixed natural resolution. Any > > other resolution that you feed to it is either dithered up or dithered > > down to match the actual resolution by the display computer in the flat > > panel. > > > > I'm well aware of that, but I would still like my video card and screen to > perform to the best of their abilities, in order to display the biggest > amount of data per second possible, without frying. Anything else > is a waste > of resources. > I think you misunderstand. If an LCD panel has a resolution of 1024x768 and you feed it 1280x1024, even though the panel can handle it, you still only get 1024x768 on the panel. In fact, you get worse because all of the sharp lines are blurred by the dithering down of 1280x1024 to 1024x768. And the human eye cannot see distinct pictures at refresh rates beyond about 30-40 frames per second. You may see flicker, but the human eye cannot even distinguish that, much beyond 65-70Hz. Speeding things up is equivalent to putting a blue fan with pretty lights that light up when it runs, inside a computer power supply. You can't see the difference, but I guess spending the extra money or just knowing it's there, is comfort food. What you really want in an LCD panel is a panel with the highest actual resolution as possible, and ignore the refresh rate. But that's expensive. Which is why so many people have crappy LCD panels. It never ceases to amaze me that people will take a perfectly good, sharp, CRT monitor that can do 1600 x 1400 or some such and toss it out and replace it with an LCD panel that is the same diagonal size but cannot do better than 1024x768, and think they have a better display. I suspect your confusing things like font size with screen resolution which is a common thing for people to do. Ted
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