Hitachi CML174SXW - Response times?!

[AgentSmith]

Hi all

I am an IT Technician in the UK and I was generally browsing the web today and over at www.overclockers.co.uk I noticed this TFT:

Hitachi CML174SXW 17" TFT Monitor (Ivory) (MO-000-HI)
The thin and sleek design of the CML174SXW TFT Monitor provides distortion-free images while saving desktop space. Features include excellent contrast ratio, fast response time and a DVI-D / D-sub input.

- 17" viewable image size (equivalent to 19" CRT)
- High Resolution - SXGA 1280 x 1024
- Excellent Contrast Ratio (400:1)
- Fast response time - tr: 12ms + tf: 4ms
- Wide viewing angle - (H) 160 degrees, (V) 160 degrees

My question stems from that response time - I'm not exaclty sure what it means by saying 'tr: 12ms + tf: 4ms' what the hell does that mean? A response time of 16 ms or what?

Just curious!

Slowdown? What slowdown? Didn't you know this was a slideshow?

 

[guru]

Yep... 16ms

 

[fireflayer]

tr: 12ms + tf: 4ms

the tr is rising and the f is falling... for a total of 16

 

[AgentSmith]

Does that not seem overly quick to anyone else?

Slowdown? What slowdown? Didn't you know this was a slideshow?

 

[bobmitch]

It is fast, when you consider the average CRT does about 13ms response time. Most LCD do 15ms up and 10 down. Believe what you will...this monitor refreshes with no ghosting or blurring.

Bob

 

[blexxun]

The P22 phosphor which is used in CRT monitors has a response time of 1...10 microseconds, thats 1000 x faster than a LC display.

LCD-TFT Displays will never reach the performance of phosphor based displays when it comes to motion blurr free images.

For those who are more interested in the technical background details about phosphor can be found here:
http://www.nichia.com/phosphor_index.html

and here

http://www.cl.cam.ac.uk/~mgk25/ieee02-optical.pdf

 

[GoSharks]

While it is true phosphor is magnitudes faster than LCD in terms of response time, on a CRT monitor the real factor is the frame rate or refresh rate so it really is not 1000 x faster.

60Hz = 16.6ms
75Hz = 13.3ms
85Hz = 11.7ms
100hz = 10ms

The phosphor on a CRT gets hit by the electron beams once every frame. When the beam moves to the next phosphor the previous phosphor starts to degrade in brightness. LCD’s stay on for the entire frame thus no flicker.

Some older CRT monitors used long persistence phosphors to combat the flicker problem and in fact had a much slower response time and showed the same ghosting and streaking we see on 30+ms LCD’s today.

Jim Witkowski
Chief Hardware Engineer
MonitorsDirect.com

<A HREF="http://www.monitorsdirect.com" target="_new">MonitorsDirect.com</A>
<P ID="edit"><FONT SIZE=-1><EM>Edited by gosharks on 12/04/02 10:41 AM.</EM></FONT></P>

 

[blexxun]

Well..the fact that the time constant of CRT displays is short compared to the frame rate is *key point*. It prevents the so called "sample and hold artefact".

Because of the ultra short response time CRTs are called "flashing displays".

This is in contrast to LCD displays which are "holding displays". Here the pixels remain "on" until they are turned "off". This holding character generates the "sample and hold" artefact which makes moving images blurred.

This effect becomes more and more invisible the higher the frame rate is. But in order to get the same amount of sharpness for moving images holding displays must be driven at a much higher frame rate compared to CRT's. This is the inherent dilemma of LCD displays.

In other words it matters very well that a CRT has a response time which is short compared to the frame rate...moving images remain sharp.

There are a lot of research activities to get rid of the sample and hold artefact for LC displays.
One solution is to make the backlighting flashing. Thats in principle no problem because the CCF lamps can be truned on and off very quickly.
Another way is to introduce black frames. This however requires quite fast LC displays which are not available for mass production right now. It has however the advantage that it can be done via the panel controller or even just by software.
All these solutions have already been presented at the SID.