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Apple Desktops Discussion of Apple's desktop machines including Mac Pro, iMac, Power Mac, and mini

iMac - My iMac Screen is very grainy?

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I just received my iMac 24in today. Still images appear crystal clear however I noticed the screen lacked crispness (very grainy – could see lines horizontal etc) when I tested the screen saver (moving images). Then later, I tried a few DVDs and the clarity again was less than par. It was very blocky-grainy-patchy (anyone of those terms applies). I played around with the resolution but it had no effect.

This is the first Apple computer I ever bought so I am hoping that I am doing something wrong and it is just a matter of adjusting a setting.

Any insight is appreciated – I will be phoning Apple tomorrow too and will post an update based on what they have to say.

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I put the cosmos screen saver on and noticed horizontal and vertical lines pulsing in waves. So as the images for the screen saver would go through transitions, behind the images I could see a constant moving of these lines. They move closer together (both vertical and horizontal) then they move farther apart. It is not as visible in color rich images but more so when the background is black.

Not sure if this is related to the lack of quality of DVD movies when played.
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Chundermuffin's Avatar
Member Since: Apr 11, 2006
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Well, I can't vouch from first-hand experience with one of these but a DVD on a screen of that resolution would probably start to look a bit grainy, depending on what's happening on-screen. If you're playing them through DVD Player, make sure Deinterlace is enabled (under the Video menu), that will help somewhat. If you can, the best way to know if there's a problem with the panel is to take the same DVDs (and maybe the screen savers too) and try them on another 24", see if the same artifacts show up.
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I talked to technical support regarding this problem. After some effort to resolve it, I was advised to take it to a local authorized dealer. At the Apple store I checked out a 24” iMac they had on display and same ‘white lines’ appeared on it.

The way to notice the problem is to choose the cosmic screensaver then test it. The higher the resolution the finer the lines but they are there. The lower the resolution the more apparent.

The technical guy from the dealership was a bit taken by the discovery – guess nobody had yet paid close attention to the screen. He said that since it was so new a few bugs should be expected and that if I wanted the kind of clarity I was talking about then to buy a Mac Pro.

I took my iMac back – and now debating on what to do. Is it too much to expect a crystal clear screen for what he said was an ‘economy’ model? Or do I buy the Mac Pro which by the way I checked out when I was at the Mac Store– the screen was crystal clear (had a separate 23” HD screen).

Any opinions?
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Member Since: Aug 30, 2006
Location: Winnipeg, MB
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The vertical line in the screen saver is due to the vertical refresh (v blank). The image is rendered at a different frequency than the screen is refreshed at and you get image tearing. The problem with the DVD sounds to be something totally different which I don't see on my display.
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I dont think its too much to ask for a screen without lines across it, I havent noticed any on mine and saying if you want better to buy a power mac sound slike a bit of a cop out.
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Marl Huss

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On my 24inch iMac I tried the Cosmos Screen saver and did not really notice anything, though you can see a feint white refresh, nothing much though. As for movies, I found it could be slightly grainy on DVD films however when I tried a 720p WMV video (Halo Wars Trailer) it seemed perfect, and there was a lot of black in that trailer...

Of course most of my DVDs are not widescreen which probably is part of the problem.
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I think best way to see what I am talking about is to choose the 640x480 (stretched) resolution and select the abstract screen saver (found it even more apparent on this vs the cosmos). I found once I set the screen resolution at 1600x1200 is when the lines were much harder to notice. If however you look at the corners of the screen, just focus for a few secs then they become visible.

Again, I am not sure if I am being too picky - the key for me is that it took me only 2 days to notice this and over time perhaps this could surface again?

Anyone with more experience on these matters - care to give insight?

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