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I had to move my laptop over to the study, and we have an old/spare monitor which we haven't used a while - the last setup that used it was a CLI only linux install - it didn't flicker much, and text was sharp.

I decided to use it with my laptop (thinkpad r61, running a plain vanilla install of windows 7 professional with none of the lenovo addons) as a secondary screen - it seems to almost imperceptibly flicker, and text looked kind of 'off' (images seemed ok).

I'm guessing part of the problem is cleartype which IIRC is being used on windows 7. The flickering on the other hand...

I only have one monitor frequency available to me - 50 hz - there's no mention of what res or frequencies the monitor supports, so i'm unsure if that's the problem. All LCDs i have run at that frequency fine tho.

It could alternately be old age - do CRTs tend to flicker when they get older?

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  • I've got a 1989 fanuc mainframe with an original crt that flickers so bad I'm honestly afraid it's going to induce a seizure.
    – Blomkvist
    May 10, 2011 at 1:42
  • not THAT old a monitor, thank god. I think this was just about the time CRTs started getting stale. 9-10 yearish?
    – Journeyman Geek ♦
    May 10, 2011 at 4:15

3 Answers 3

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50 Hz is definitely slow enough for a wide range of people to notice flickering. CRTs always flicker, but at 72+ Hz few people notice it.

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  • there dosen't seem to be an option to set anything but the default refresh rate on windows 7 on a dual screen setup on my laptop. I should probably give it a test with a real machine, or mess around with unsupported settings... what's the worst that could happen? :)
    – Journeyman Geek ♦
    May 10, 2011 at 3:05
  • The laptop video card probably needs to run both RAMDACs (panel and external) at the same refresh rate, so trying a different machine (without a built-in panel) would probably be best.
    – Ignacio Vazquez-Abrams
    May 10, 2011 at 3:45
  • would a dual output desktop card have the same issue? and can i use a DVI -> VGA adaptor?
    – Journeyman Geek ♦
    May 10, 2011 at 13:24
  • It probably would, but it would have a higher refresh rate. A DVI -> VGA adapter does not change the refresh rate.
    – Ignacio Vazquez-Abrams
    May 11, 2011 at 0:03
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You need to set the Screen refresh rate to something higher than 60 for 15" monitors and higher. The larger the monitor the faster the better. It has to do with the time it takes to redraw the screen, and on 17" or better 60 times a second is just to slow and your eye will notice the changes in energy being refreshed. It could also be because a fluorescent lighting fixture is near with its odd/even ballast refreshing in sync to make things look weird. 85Hz is what it takes for me to be comfortable with a CRT.

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  • nice catch. its a 17 inch monitor. there's also a florescent lighting fixture - i will test with it switched off as well.
    – Journeyman Geek ♦
    May 10, 2011 at 3:11
  • did a little testing, and no, the lamps, or any nearby electrical appliances have no effect in my own case.
    – Journeyman Geek ♦
    May 13, 2011 at 4:37
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While its not an acceptable solution, and Ignacio's answer is the most correct possible, apparently you can get around low refresh rates by lowering the resolution of the monitor - 800x600 works alright at 50 hz (the monitor in question goes up to 1280x1024). According to pctechguide, i need at least 82 hz vertical refresh for the monitor to not flicker at its maximum resolution.

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  • My eyes are more sensitive... 640x480@60hz is pushing it for me. Any higher resolution at that refresh rate, or any lower refresh rate at that resolution drives me crazy. For CRTs, I'm not comfortable unless I have at least 75Hz minimum at 1024x768, 80 for much higher resolutions.
    – TuxRug
    May 13, 2011 at 4:23
  • oh, its not perfect, it just is less terrible - the 'right answer' is still to increase the refresh rate.
    – Journeyman Geek ♦
    May 13, 2011 at 4:36
  • hm. apparently the darn thing suddenly allowed me to set 85 hz at 1024x768... which while awesome, wasn't there before.
    – Journeyman Geek ♦
    May 13, 2011 at 5:01

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