[ltp] X60 produces fuzzy VGA output in high resolutions - will Ultrabase help?

[Richard Neill]

Shot (Piotr Szotkowski) wrote:

> And it’s not fuzzy in a way that rescaled image is fuzzy, it’s way more 
> subtle; you can perfectly make individual pixels, it’s just that their 
> edges are a little bit out of focus (compared to the internal LCD, which 
> is totally sharp, or the same external LCD in higher refresh rates, 
> i.e., lower resolutions).

OK - that eliminates that possible problem. So what we have is some kind 
of analog signal quality issue, rather than a config problem.

> 
>> You might also check your cable setup - if you see ghosting 
>> (typically, edges appear to "echo" faintly a few cm to the right) 
>> - you need to use a better VGA cable. Importantly, you should only
>> use 1 VGA lead, and never join them, as you get reflections from the 
>> impedance mismatch at the connectors.
> 
> It’s not ghosting, though. My LCD (Eizo S2031W) can scan the signal it 
> receives over the analogue input and try to match the proper phase and 
> clock, and it makes much, much better job at it the higher the refresh 
> rate – that’s why it works so well with 75 Hz resolutions and so bad 
> with 60 Hz ones. I tried setting the phase by hand, but the auto sync 
> usually chooses the best one (and the image is fuzzy anyway).

You might still want to try a better (or shorter) VGA lead.

Also, have you played with xvidtune on the thinkpad itself?

> 
> It’s best seen on a 1×2 px black-and-white ‘checkers’ – the image even 
> ‘floats’ in lower refresh rates when the disk is active (much like the 
> TV image ‘floated’ a bit sometimes when it was on air antenne in my 
> childhood years).
> 
>> You might also consider a USB-DVI adapter.
> 
> I was wondering about this option. Will it work with the Intel
> graphics in X60, and will it work under Linux (Ubuntu in my case)?

I don't know.

> I vaguely remember reading somewhere that the analogue signal at the 
> ultrabase’s VGA output is of higher quality that the one from the 
> internal port – even though they both are originating from the same 
> chipset. (It’s so irritating that I can’t simply get an X6 and check…)

It is possible there's a buffer somewhere, but I'd be a little surprised.

> 
>> Lastly, the refresh rate for an LCD shouldn't matter too much.
>> (Unless you're a gamer and really care about pixel response times). 
>> Refresh-rate mattered with CRTs to reduce flicker, but LCDs don't 
>> flicker anyway.
> 
> Yeah, and usually the LCD screen refreshes less often than the
> lower refresh rate anyway. I know the theory, but I see what
> I see; apparently, the quality of the signal from the VGA port
> at the lower refresh rates (higher resolutions) is so much worse
> that my LCD’s analogue-to-digital converter can’t make the same 
> conversion from it.

That would be the SQRT(n) factor of signal:noise ratio. More samples per 
second => less noise.

> 
> My reasoning for trying the ultrabase is the below:
> 
> 1. The cable is ok, as the image is clear at higher refresh rates.
> 2. The chipset is ok, as it can produce images at 1600×1050 px.
> 3. So, maybe, the flaw is in the internal VGA port, and if I used
>    an external one the image would be clear at 60 Hz as well.
> 
> (I can see that 1. might not be true, though.)
> 
> If only the X6 wasn’t so expensive (especially for a glorified
> digital-to-analogue converter…), or was equpped with a DVI port…
> 

Do let us know what you find.

Richard



P.P.S. Are you using antialiased fonts? If so, that makes it much harder 
for the LCD monitor to auto-adjust, as there are far fewer hard vertical 
lines to sync the clock to.

Here is a "chessboard" - alternate black/white pixels.
http://www.richardneill.org/a22p-mdk11-0_files/lcd-cal-1280x1024.png
View it at 100% size, and try getting the monitor to adjust correctly
(either auto, or manual clock). Then keep that setting.

Personally, I prefer non-antialised (but correctly hinted) fonts anyway.