NEC L1550V Resolution?

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I have a flat screen monitor NEC L1550V whose manual says one of its
resolutions is 1024X768.  That sounds digital to me.  I thought since
its only input is VGA that it is analog.  



Big Fred

Re: NEC L1550V Resolution?

Quoted text here. Click to load it

You misunderstood.  The manual lists a resolution of 1024X768
pixels, determined by display hardware.  It does not matter whether
the source signal is analogue or digital.  (This reminds us why we
need drivers, to interface between the source signal and the monitor's
hard-wired circuitry.)

Don Phillipson
Carlsbad Springs
(Ottawa, Canada)

Re: NEC L1550V Resolution?

Frederick wrote:
Quoted text here. Click to load it

If you use Monitor Asset Manager (moninfo) from,
it shows the resolutions too. This is what my monitor shows
(native format being 1280x1024). The program can actually
probe the EDID table from the monitor, to get these values.

Standard timings supported
      720 x  400p at  70Hz - IBM VGA
      640 x  480p at  60Hz - IBM VGA
      640 x  480p at  67Hz - Apple Mac II
      640 x  480p at  72Hz - VESA
      640 x  480p at  75Hz - VESA
      800 x  600p at  56Hz - VESA
      800 x  600p at  60Hz - VESA
      800 x  600p at  72Hz - VESA
      800 x  600p at  75Hz - VESA
      832 x  624p at  75Hz - Apple Mac II
     1024 x  768p at  60Hz - VESA
     1024 x  768p at  70Hz - VESA
     1024 x  768p at  75Hz - VESA
     1280 x 1024p at  75Hz - VESA
     1152 x  870p at  75Hz - Apple Mac II
     1152 x  864p at  75Hz - VESA STD
     1280 x 1024p at  60Hz - VESA STD

The 1024x768 is a VESA resolution (VESA is a standards body).

The "p" stands for progressive, since LCD displays are normally
progressive scan for computer monitors. If the letter "i" was there,
that would be interleaved, meaning there are odd and
even frames being displayed in succession. Interleaved,
is what an old television used.

There are multiple entries, because the display supports
"multisync" and operates at more than one resolution. At
the LCD panel itself, it supports only one resolution, the
"native" resolution of 1280x1024. There are actually 1280
columns by 1024 rows of pixels, switched on and off. The
intensity of a pixel, might be adjustable with a 6 bit or
an 8 bit number for each color.

The other resolutions are achieved by "scaling" the image to
fit the native resolution. The image doesn't look as sharp
at the non-native resolution, due to the scaling process.

In terms of refresh rates, the panel has limits on that too.
One of the sites, perhaps Xbitlabs, claims when operating at
a higher refresh rate, the panel throws away "1 in N" frames,
to drop the actual refresh rate down to 60Hz. But some modern
panels (more modern than mine), support higher refresh rates
than that, so may not need to throw anything away.

These are the processes possible on the display path. DAC
is digital to analog conversion. ADC is analog to digital
conversion. Scaling is still needed on the VGA path, because
the number of rows of pixels and the number of scan lines,
don't match.

    <--- Video card ---->                    <------ LCD monitor ------>

    GPU (digital) --- DAC --- analog,VGA --- ADC --- scale --- raw_panel

    GPU (digital) ----------- digital,DVI ---------- scale --- raw_panel

The digital path would be "perfect", if the scaling step could be
skipped, and if you select the native resolution value, which
in my case is 1280x1024, then no scaling is needed and the scaler
disappears from the picture. In the analog path, if you select
native resolution, there is still some room for color inaccuracy
due to the DAC and ADC steps. But the human eye is so accommodating,
you'd hardly notice.


Inside the raw_panel, there are more analog processes involved.

    "The column and row wires attach to transistor switches,
     one for each pixel. The one-way current passing characteristic
     of the transistor prevents the charge applied to the pixel from
     draining between refreshes to the display image. Each pixel is
     a small capacitor with a layer of insulating liquid crystal
     sandwiched between transparent conductive ITO layers."

So there's "lots of digital *and* analog" in that picture. The
capacitor for each pixel, holds an analog voltage level.


Re: NEC L1550V Resolution?

Thanks guys.

Big Fred

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