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I've just got my new 2011 iMac (OS X 10.6.8), but connecting my HP LP2475w via a mini DisplayPort to DisplayPort cable leads to a very fuzzy screen. It's the correct resolution and refresh rate (1920x1200, 60Hz), and size-wise, everything looks fine on the monitor. However, everything, especially the text, looks horribly blurry. It's almost as if the iMac is outputting a 1920x1199 image or something, and the display is stretching it slightly. Like what used to happen with old CRT monitors when you set the image 1px too tall/wide.

Here's an image of what I see

And here's how it should look

enter image description here

Does anyone know what the issue could be?

Thanks!

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Have you taken a picture of part of the screen using Grab and examined it (or used the digital color meter) - you should be able to see if the text is drawing on the pixel boundaries. LCD off by one errors are far worse looking than CRT! Font smoothing in the appearance preference pane might be worth checking if only text is the issue. –  bmike Jul 18 '11 at 13:30
    
You mean take a screenshot of the screen? I have, it looks exactly like the iMac's screen. And I'm pretty sure it's both text and images. I've tried all the options for the command demonstrated here, to no avail. I'm hesitant to order a mDP -> DVI converter from Apple, since it's still a digital signal, right? So it shouldn't make any difference? Thanks! –  Ashley Williams Jul 18 '11 at 14:07
    
Screenshot incase there's something I'm missing: dl.dropbox.com/u/891742/Screenshots/39yd.png –  Ashley Williams Jul 18 '11 at 14:14
1  
Apparently others are having the same problem as me, with the same hardware, and they said it worked fine before 10.6.8, so I guess I'll wait to see if Apple releases a fix. Thanks! –  Ashley Williams Jul 18 '11 at 14:32
1  
I realised today that I had asked a friend about the issue before updating to 10.6.8. So I'm not entirely sure my issue is the same as the one I previously referred to. Added some images to my question too, to demonstrate the issue. (P.s. can you upvote this comment please so I have >10 rep and am able to attach actual images instead of linking to them. Thanks!) –  Ashley Williams Jul 21 '11 at 19:44

2 Answers 2

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You're not connecting with a VGA cable, are you? Mini Display Port to VGA adapter to VGA-in on the monitor? Because if so, it might very well BE approximating the resolution to an actual X-by-Y that isn't a native multiple of the screen pixels.

The giveaway about that is regular vertical stripes of fuzziness. Not the only giveaway, but if you have blurry streaks, you need a DVI cable.

EDIT: Reading your comments on the question, I'm now certain. Using DVI will solve this.

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I'm not using a VGA cable, it's a mini DisplayPort to standard DisplayPort cable. –  Ashley Williams Jul 21 '11 at 20:10
    
You were right. This £10 mDP->DVI converter does the trick. I believe my monitor has a poor DisplayPort implementation, since only this brand/model has any issues to my knowledge. –  Ashley Williams Sep 3 '11 at 14:48

[Edited - it looks like the original pictures are gone - some of this may not make the most sense without the original pictures - my apologies]

Awesome screen shot - that shows the software settings are perfect. You can be sure of that by opening the System Profiler app and looking at the Graphics / Displays data when the external is connected.

Your screen shot is nearly identical to mine - I am not using LCD font smoothing and the slight difference in color values could easily be color calibration differences. The pixels two above and two below the one selected are one or two darker on my display as compared to your screenshot.

Here is a magnification of both - mine on the bottom and your picture on the top.

ashley mike

Even though it's unlikely - I would make sure it's not a timing issue by the following.

  • disconnect the cable, adapter and power off the monitor
  • power on the external monitor
  • connect the cables and adapter to the monitor
  • plug in the whole works to the mac

Sometimes when a mac wakes from sleep, you get snow or other artifacts on rare occasion if the mac detects the monitor capabilities from the adapter and sends signal before the monitor can react (or is still scanning other ports if it's got multiple inputs).

Now - the real cause is likely cabling / adapter / monitor. You'll have to test that by eliminating / borrowing / replacing them one by one. :-( Either that or some bizarre software driver issue. That also will be a tough one to pin down unless it's a popular monitor and you just updated software.

Did this display ever work well for you with your mac? Does the pixelated font rendering move or os it perfectly static and repeatable each time the menu is drawn?

I have seen electrical noise cause that - bad shielding or cables/connectors or more likely noise on the ac power from a large motor or wiring issues.

This is a real stumper since it happening on multiple macs and multiple monitors.

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