down the LCD panel rabbit hole
brian
fedora at logi.ca
Tue Aug 11 04:53:25 UTC 2009
On 08/10/2009 09:35 PM, Tim wrote:
> On Mon, 2009-08-10 at 19:38 -0400, brian wrote:
>> I'm also pretty confused as to why there are 2 separate display config
>> panels in the first place.
>
> System preferences - set up drivers and configuration for what your
> hardware actually is.
>
> User preferences - allows users to have custom resolutions to suit
> themselves, such as users with eyesight problems who want everything
> big. If a user doesn't set their own preferences, the default is to
> give them the highest resolution available.
I sort of understood it that way. My confusion was mainly that the two
resolution select lists didn't seem to correspond. I see, now, that it
was because my xorg.conf was messed up. Or, I assume that was it.
One thing, though: when I finally got it right (see my other response)
the resolutions selected were both different as well as being a lot
lower than the max.
> Though, LCDs only work well at their physical resolution. Even exact
> multiples of double or half resolution look disgustingly smudgy. CRT
> monitors often work well at several different resolutions, they don't
> have 1:1 mapping of graphics pixels to the dots of screen phosphors.
Which would explain why it was so blurry earlier. It looked pretty
miserable.
> You also mentioned frame rates. It's usual that LCD panels only work at
> one frame rate (60 Hz being common), compared to CRTs which often work
> across a few different rates. Most graphics cards have an array of
> different screen sizes and frame rates, with there being combinations of
> some of them that they cannot do (e.g. it may do high resolution *or*
> fast screen rates). If your card only offers your desired resolution at
> a different frame rate that your monitor users, you can't use that
> screen mode. That's why some people find that their desired resolution
> is unavailable to them.
The manual for this panel lists:
Mode, H Freq. (kHz), V Freq. (Hz), Pixel Clock (MHz), Sync Polarity (H/V)
640 x 350 31.47 70.09 25.18 +/-
640 x 400 31.47 70.09 25.18 -/+
640 x 480 31.47 59.94 25.17 -/-
640 x 480 31.50 75.00 31.5 -/-
720 x 400 31.47 70.08 28.32 -/+
800 x 600 37.88 60.32 40.00 +/+
800 x 600 46.880 75.00 49.50 +/+
1024 x 768 48.36 60.00 65.00 -/-
1024 x 768 60.02 75.03 78.75 +/+
1152 x 864 67.50 75.00 108.00 +/+
1280 x 1024 63.98 60.02 108.00 +/+
1280 x 1024 79.98 75.02 135.00 +/+
1920 x 1080-R 66.587 59.934 138.50 +/-
1920 x 1080 55.62 49.92 141.50 -/+
I'd come across someone else's xorg.conf for use with this same LCD.
However, their numbers (eg. dot clock) were slightly different. And I
was stumped as to where xorg.conf's "HTimings hdisp hsyncstart hsyncend
htotal" numbers came from. Rather than blindly follow along with this
person's config, I eventually found a reference to the cvt utility. I ran:
cvt 1920 1080 55.62
... to get those figures.
This is just for posterity in case someone else needs the info.
Thanks for the reply, btw.
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