Problem with Macbook Pro and external Monitor

Discussion in 'Mac Accessories' started by macbook123, Apr 27, 2006.

  1. macbook123 macrumors 68000

    Feb 11, 2006
    I got a Samsung 204b monitor today with 1600x1200 resolution and a 5 ms refresh rate (corresponding to 200 Hz). Now I'm utterly confused because the display preferences let me only select a 60 Hz refresh rate for this monitor. According to the DAC speed of the graphics card installed (RadeonX1600) this computer should be able to support up to 208 Hz. So why is my MBP limiting me to 60 Hz?

    Thanks in advance for any information input.
  2. macbook123 thread starter macrumors 68000

    Feb 11, 2006
    Alternatively, what's the maximum refresh rate I should be able to get to work? For instance does anybody own an Apple display and can tell me what their maximum rate is? If I get only 60 Hz out of the 1600x1200, the rate for the 23 inch screen should be 50 Hz or so and the one for the 30 inch one should be 30 Hz. This would be clearly unacceptable.
  3. PatrickF macrumors 6502

    Feb 16, 2006
    The 208Hz refers to the video bandwidth, not the refresh rate. 60Hz I believe is pretty normal for LCD screens. There's not much (if any) point in going higher.
  4. Chundles macrumors G4


    Jul 4, 2005
    Refresh rate on an LCD means something competely different than for CRT's. 5ms refers to how quickly a single pixel can change colour, it has nothing to do with how quickly the whole screen is refreshed.

    As the guy above says 60Hz is normal for an LCD and does not have any bearing on the 5ms refresh rate of the individual pixels. Everything is fine, carry on.
  5. macbook123 thread starter macrumors 68000

    Feb 11, 2006
    Thanks for the info! Yesterday I was just a little disappointed because the picture on the new screen looked awful. Figured out now that this was just sub-optimal settings.

    By the way, can anyone tell why one gets a lower refresh rate the larger the monitor gets? Why is it 60 Hz on a 1600x1200 screen, as opposed to, say, 100 Hz?

    It seems the other crucial question is, what is the 5ms `refresh rate for individual pixels' good for? If 60 Hz, corresponding to 16.6 ms, is the `refresh rate for the entire screen', how can it make a difference that individual pixels refresh more quickly?
  6. Chundles macrumors G4


    Jul 4, 2005
    Forget about full screen refresh, it's not something you have to worry about with LCDs.

    The faster the individual pixels refresh on an LCD the better movement will look. Slower screens mean that as something moves across the screen the pixels take a visibly noticeable time to change colour - this results in ghosting behind the moving object. 5ms is very bloody good. The shortest I've seen is 4ms although most people say they can't tell the difference between 8ms and 4ms screens so the extra money for the quicker screen isn't really worth it - although for gamers and video people it would make a big difference I suppose.

    Does the screen look OK now?
  7. After G macrumors 68000

    After G

    Aug 27, 2003
    Refresh rate for an LCD monitor basically doesn't matter, because the pixels are all on all the time.

    Refresh rate really refers to the number of times per second the electron gun in a CRT could sweep over the screen and reenergize all the phosphors on the screen.

    Since all the pixels in an LCD are on all the time, the individual pixel rate is more important as they are all responding independently to input. If you have changes on your screen that take less time than your LCD's pixel refresh rate, you will notice. Like in 3D games where ghosting will occur.
  8. macbook123 thread starter macrumors 68000

    Feb 11, 2006
    Yes, thanks, it looks pretty fine. The main problem was I had it at too high a contrast setting and that made images and especially fonts appear irregular accross the screen. Never had a screen with that high a contrast ratio (800:1) so didn't expect that I had to turn down the contrast :)
  9. matticus008 macrumors 68040


    Jan 16, 2005
    Bay Area, CA
    Because your other questions have been answered relatively accurately, I'll focus on this one. The basic idea is that the higher the resolution, the longer the electron gun takes to make a pass in a CRT.

    For example, if you run a given monitor at 768 lines, the gun can refresh at say, 100Hz. If that monitor supports 1200 lines, the gun's beam has to compress into a smaller vertical confinement, but the movement of the gun stays at roughly the same speed, which means that the overal refresh movement is slower as a result.

    Of course, none of this is applicable to LCD displays.

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