Talk:Refresh rate

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Question about the refresh formula[edit]

Could someone can explain this :

The refresh rate can be calculated from the horizontal scan rate by dividing the scanning frequency by the number of horizontal lines multiplied by 1.05 (since about 5% of the time it takes to scan the screen is spent moving the electron beam back to the top). For instance, a monitor with a horizontal scanning frequency of 96 kHz at a resolution of 1280 × 1024 results in a refresh rate of 96,000 / (1024 × 1.05) ≈ 89 Hz (rounded down).

96,000 = horizontal refresh rate 1024 = number of horizontal pixels 1.05 = ? the time it takes to scan the screen is spent moving the electron beam back to the top

Who is "IT" ? The spot of the CRT ? Are you speaking about vertical balnking ?

Which unit of measurement is this "1.05" ? time (in which unit : µs, ms... ?) Coefficient (based on ??) ?

For example if I take CRT TV at 15khz of horizontal refresh rate who display 240 lines (progressive) I must obtain 60hz of vertical refresh rate...

15625 / (240 x 1.05) = 62... not working... I must take 1.07 to make it works. Someone can make some clarification about this ?

Displaying Movie Content on TV[edit]

I think it would be great if someone could expand on this section. Especially if this were explored in detail: "If the 120 Hz rate is produced by frame-doubling a 60 frame/s 3:2 pulldown signal, the uneven motion could still be visible (i.e., so-called 6-4 pulldown)." I have noticed this is a problem in new HDTVs with high refresh rates, but am not proficient enough to explain it well. Polancox (talk) 19:36, 3 April 2010 (UTC)

Question[edit]

Could someone make a photo of a refreshing CRT (with a very short exposure)? In the long term a diagram/picture would probably be better, but even a photo would help. Paranoid 16:14, 21 May 2005 (UTC)

Video Refresh Rate[edit]

In looking at different display's I keep coming across the same thing for video refresh rate 1 FH, 2 FH, and 3 FH. Does anyone know what this means?


File:Video Refresh Rate.JPG


What is this from, some kind of projector? Beyond 800x600, 60 hz was never the most common refresh rate in use, so this 60 hz limit on this can't be that of a normal monitor. All I can guess about the "FH" is that it seems to correspond to the horizontal refresh rate of the different formats - ie the time it takes to scan a single line. This is about the same for NTSC and PAL, double for progressive scan NTSC, PAL, and 1080i, and triple for 720p. But those aren't exact, so if that is it, then I don't see why this representation is useful. Algr 17:30, 16 March 2006 (UTC)

The image is from a plasma manual. I've seen these specifications for projectors and I believe LCD display's as well.

Refresh rate and field rate[edit]

Are these two articles about the same thing? --JDtalkemail 22:08, 10 June 2006 (UTC)

No, only interlaced monitors have a field rate. Algr 15:12, 30 June 2006 (UTC)


Spreadsheets[edit]

I don't think that this belongs here, except as disambiguation. You could also have a section on how quickly various soft drinks end your thirst, but it is still off topic. Algr 19:01, 21 July 2006 (UTC)

I disagree. I think it makes sense to give a variety of examples of the technical use of the concept refresh-rate. -69.87.200.180 18:18, 19 August 2007 (UTC)

Eyes[edit]

It says that 60hz can cause eye strain but i would like it to go more in-depth, also will 60hz on a lcd screen cause any eyestrain? -(someone wrote sometime)

Any flickering that the eye can perceive, even subliminally, can have adverse effects. So 60 Hz is a problem. 85 Hz and above is generally no problem. 72-75 Hz should mostly be kind of OK. But it seems that this does not apply to LCD because each LCD pixel has its own memory and can stay on all the time. -69.87.200.180 18:18, 19 August 2007 (UTC)

Even with LCD displays, low refresh rates like 60Hz can cause eyestrain due to brightness adjustment which changes PWM modulation of LCD's backlight (i.e. its not on 100% of the time). Too low brightness can result in sub-60Hz rates that will cause eyestrain. —Preceding unsigned comment added by 69.106.237.110 (talk) 00:40, 4 April 2011 (UTC)

Computer Displays Section[edit]

This might seem a bit silly, but I don't think you mean to say that Windows 2000 is a descendant of Windows XP. Thelbert 20:25, 20 October 2006 (UTC)

Refresh rate = Max. FPS?[edit]

Are the display's refresh rates limiting the FPS when (as example) gaming? Skies 19:40, 2 January 2007 (UTC)

Yes. If the graphics card generates more frames then the monitor can display, some frames will get skipped. They will exist in the VRAM, but never transmitted to the monitor. The smoothest graphics occur when the game FPS and the monitor's refresh rate match exactly. Algr 04:58, 3 January 2007 (UTC)
It depends. If the monitor is drawing a frame and the graphics card sends a new frame, the monitor will start to draw this new frame in the middle of the process. In the end, you'll have a full-frame that is, in fact, a mix of many frames rendered by the graphics card. That's why 'vsync' makes the animation smoother, because it perfectly synchronizes monitor and graphics card. Remember that 'vsync' is different from having refresh rate number equals to frame rate; if they aren't perfectly synchronized the problem remains. —The preceding unsigned comment was added by 201.19.193.36 (talk) 21:14, 1 March 2007 (UTC).

Eye Perception[edit]

It would be intresting if there was any information regarding how the eye and brain percepts the image according to the refresh rate. Such as the human eye can notice a flicker at 50hz but perhaps not at 100hz depending upon screen size. —The preceding unsigned comment was added by 81.179.64.155 (talk) 18:25, 21 February 2007 (UTC).

Black most of the time?[edit]

Im not sure if this statement is totally correct: At any given time, most of a TV's screen is actually black.

The picture actually shows a fading band near the top of the screen, but there is still some light coming from the other parts due to the phosphor on the tube. (and you can see it on the screen)

There is a certain amount of afterglow, but the vast amount of light is coming from the narrow band that has just been scanned. This comes out overexposed in this shot. If I'd lowered the exposure to see the area just being scanned clearly, you wouldn't see the afterglow. Algr 09:18, 21 April 2007 (UTC)
Yes but the statement about being 'black'(implying emitting no light at all) is not quite correct is it? Why not say 'most of the screen area emits only a small amount of light due to the persistence of the phosphor' Also it may be good to mention the main effect here which is that of persistence of vision. —The preceding unsigned comment was added by VirtualEarth (talkcontribs) 11:57, 21 April 2007 (UTC).
Or 'The light emitted from the screen is due to the phosphorescence of the coating on the tube face. This light decays very quickly after the electron beam has passed, and the subjective effect of a completely bright screen is due to persistence of vision'.

Virtual Earth

"Black" doesn't mean "no photons at all", even a black hole emits some photons. Black is always a relative term. For example, if you project an image of a black cat on a white screen, the cat will still look black even though the wall reflects more photons then it would if the projector was off. Similarly, all the light you see from a TV comes from short bursts of light 30 times a second, while the phosphors are inactive most of the time. Algr 18:37, 11 November 2007 (UTC)

Pixel memory and strobes[edit]

There are two separate, basic concepts here. One is, how often a display changes. The other is, what happens in-between the changes.

CRT displays are very peculiar because a big complicated picture is painted by a tiny, single spot, moving very fast in a repetitive manner. So, almost all of the screen is "off" almost all of the time, conceptually.

Modern LCD displays seem to be very different, with each pixel containing memory. But the concept of rows and columns is very important here, with the data being strobed in to each location in turn. Maybe older, original LCD displays did not have memory in each location?

Most basic LED displays do not have memory, but strobe each location with rows and columns, with much flicker. There are probably fancier more modern LED TVs etc that do have per-pixel memory.

I'm not sure how modern plasma TV displays work; someone should add this to the article.

Although "refresh rate" commonly applies to rows and columns on a regular grid, it can also apply to other geometric arrangements, such as 7-segment displays, or indeed to any set of information at all which is updated on a regular basis.

These articles are particularly informative about LCD refresh issues:

  • LCD Resolution: When Bigger Is Actually Smaller, 2004 [1]
  • Analog and Digital CRT and LCD/TFT PC Monitors, 2007 [2]

Please add such resources to the article. -69.87.200.180 19:45, 19 August 2007 (UTC)

120 hz displays[edit]

These new plasma displays do NOT simply display the images in a more even pattern. They actually analyze the motion of objects in the film, and simulate High Motion with new frames with objects in intermediate positions to where they were in the actual frames of the movies. The results can be VERY strange looking - it's like a totally different film shot with video cameras instead of film. The technology is something like what VidFIRE uses to make teleciene recordings look more like the original video broadcast. As a result, you can sometimes see things in the film that were not visible even in the theatre due to camera motion. Algr 18:44, 11 November 2007 (UTC)

I made a page about it. See Motion interpolation and add info if you have it. - Peregrine Fisher (talk) 01:33, 6 February 2008 (UTC)

50p or 50 Hz in the image[edit]

Is it supposed to be "p" or "Hz"? The article repeatedly talks about 50 Hz, so I think the image says the wrong thing. - Peregrine Fisher (talk) 06:25, 6 February 2008 (UTC)

Need to refresh pixels in LCD[edit]

Is this sentence correct?

"The shutters themselves do not have a "refresh rate" as such due to the fact that they always stay at whatever opacity they were last instructed to continuously, and do not become more or less transparent until instructed to produce a different opacity."

In Computer Graphics, Principles and Practice, Foley, van Dam, Feiner, Hughes, Addison Wesley, 1996, at page 162 it says "once the crystals [in passive LCD without backlight] are lined up, they stay that way for several hundred milliseconds, even when the voltage is withdrawn (the crystal's equivalent of phosphors'[in CRT] persistence). In addition, U.S. Pat. 6,452,582 says "Passive LCD pixles begin relaxing immediately after being refreshed." See Col. 1, lines 56-57.


Someone has to re-write the part about "LCDs not having Refresh rate but an equivalent is Response time". This is incorrect; while they do have response time and their refresh does not work as in CRTs technologically, they do have a refresh rate too which is I see here in the case of a laptop 60Hz on windows spec info. *This is after all also supported in the LCD wikipedia article. --AaThinker (talk) 19:04, 3 May 2009 (UTC)

Citation needed regarding Blind configuration[edit]

Settlers 4 was once such game that tended to launch at excessively high resolutions. Thankfully, the ini file could be patched manually to allieviate this problem. —Preceding unsigned comment added by 143.239.102.198 (talk) 11:15, 30 January 2010 (UTC)

definitions in last part of top section: clarify or remove?[edit]

<quot>This could mean a programmed computer interface, an event, or a mind frame, brain or mind map. 

Refresh is to restore a program to a fresh platform.

Refresh is also known as clearing, cleaning, and creating.</quot>

Some of the above is confusing and possibly not relevant ("refresh rate" of a "mind frame, brain or mind map"? Not sure what this would mean. The rate at which new data displays in a web application might be something to keep, but I think we should remove the rest.--Skwuent (talk) 18:45, 1 May 2013 (UTC)

600Hz LCDs[edit]

As far as I know, there are currently no 600Hz LCD displays. There are "600Hz Plasma Displays" but that does not represent refresh rate, rather the pulsing rate to keep the phosphors glowing. The fastest LCD refresh rate I know of is 240Hz and the fastest true refresh rate that I know of is 144Hz. I could be wrong, though. --Phopojijo (talk) 21:40, 10 October 2013 (UTC)

Cathode ray tubes section lacks any kind of references[edit]

As already stated above people already have questions regarding the "formula" and for the part about updating the NESs videochip: single background parallax effects already show that it is possible to at least modify some of the attributes during Horizontal blanking interval. NESFreak (talk) 09:33, 19 October 2014 (UTC)