refresh cycles and LCD

[Andrews, A.S.]

I think that is saying that the convention is still to send data to the display in a raster (line by line) scheme. The LCD pixels will remain constant unless the data for that pixel changes, regardless of refresh rate. In practice I have only experienced a narrow range of refresh rates acceptable to LCDs (60-75Hz).

I suppose that if you were starting from scratch and not supporting analogue CRTs, you could do things differently and have some sort of direct link between the graphics memory and the display, and maybe this exists for specialised embedded applications but personally I have not come across them.

Incidentally, if you do find a 'refresh rate free' display, how would E-Prime handle presentation timing?

Regards

Tony. 

-----Original Message-----
From: Yoav Bar Anan [mailto:baranan at post.tau.ac.il]
Sent: 24 November 2004 11:19
To: Andrews, A.S.; e-prime unofficial forum
Subject: Re: refresh cycles and LCD


In
http://www.necmitsubishi.com/support/css/monitortechguide/index04.htm
It is written that:
"Since LCD monitors do not employ phosphors, refresh rate is not a concern.
Basically, the transistors in the LCD remain open or closed as needed until
the image changes. This can be a point of confusion for some consumers,
however, since most graphics cards still "ask for" a refresh rate setting.
This is due to the analog nature of existing graphic cards and their support
for CRT displays. While refresh rates do not apply to LCD monitors, most
LCDs are set up to accept any settings from 60Hz and above".

I'm confused, does it mean I can find graphic cards that can allow no
refresh-cycle when using LCD?

Yoav

----- Original Message -----
From: "Andrews, A.S." <asa8 at leicester.ac.uk>
To: "Yoav Bar Anan" <baranan at post.tau.ac.il>; <eprime at mail.talkbank.org>
Sent: Tuesday, November 23, 2004 2:14 PM
Subject: RE: refresh cycles and LCD


Hi

No, that is not quite right. An LCD screen still receives the signal in the
same way, i.e. frame by frame at a particular frequency, usually 60 or 75HZ.
If the computer changes the contents of the graphics memory in mid-frame
this will still lead to display errors. This is true for analogue or digital
connections.

Where LCDs differ is that they have a constant backlight and so are not
subject to flicker in the way that phosphor displays (CRTs) are. The 16ms
you refer to is the response time of the LCD pixels. Various manufacturers
define this in different ways, but I think it is becoming accepted for this
to mean the time it takes to turn from fully-off to fully-on and back again.
16ms is particularly fast, with many panels that are currently in use
(particularly cheaper ones) having response times of e.g. 40ms. For this
reason, CRTs are still my preferred display device. Also, LCDs have a
relatively short life, particularly the backlight, so if you are planning a
purchase, make sure you get a good warranty plan.

Regards

Tony Andrews
Senior Computer Officer
School of Psychology
University of Leicester.

-----Original Message-----
From: eprime at mail.talkbank.org [mailto:eprime at mail.talkbank.org]On
Behalf Of Yoav Bar Anan
Sent: 23 November 2004 11:47
To: e-prime unofficial forum
Subject: refresh cycles and LCD


Hi

I was told that unlike CRT screens, LCD screens do not use refresh-cycles.
Rather, any request to paint the screen is transmitted immediately to the
screen, and after a certain delay (16ms?) the screen applies the paint
request. It means that on LCD, there is no obligation for the durations to
be a product of the refresh-duration. Is it true?





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