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27" display broke? Calling owners!

0098386

0098386

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Original poster
Jan 18, 2005
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Picked up the 27" high-end stock iMac yesterday. It's mighty beautiful and damn powerful too (runs all my games on max and never dips below 60fps!) Problem is as it was downloading those games I noticed some display artefacts and I was wondering if other users could view this screenshot and tell me if you get the same problem as my photo;
IMG_6844.JPG

(click to enlarge)
URL> http://satansam.co.uk/ftp/IMG_6844.JPG

The blue graph lines seem to repeat over onto the blue background. The screenshot produces the same effect under Windows 7 as it does OSX. There are no other problems, as I said games (TF2, L4D2, Portal 2, Burnout Paradise etc) all run totally fine.

If it's a common problem then I'll just stick with it. Else I'll make use of my Apple Care and take it back. It's the only thing that's dampening this brilliant machine :eek:.
 
Yess I can see the lines, but if you can see these lines "in a screenshot" is not the monitor, is something wrong with the software…
 
qap said:
Yess I can see the lines, but if you can see these lines "in a screenshot" is not the monitor, is something wrong with the software…
Click to expand...

It's not that, if you zoom into the screenshot or move the image off the side of the screen (or just cover up the graph lines) then the glitch lines disappear. I've viewed this screenshot on my iPod and PC to test it out; they don't have the lines.
 
well ican see the lines wen when i zoom in. But its a screenshot so i see what your seeing right?? you would need an identical machine doing the same thing at the same time. then you can see if its normal or only your machine
 
The-Pro said:
well ican see the lines wen when i zoom in. But its a screenshot so i see what your seeing right??
Click to expand...

The screenshot is what the GPU is pushing out so that'll bypass any display issues. If you see the glitch lines then you've got the same problem.

The photo is what my monitor displays.
 
Is this photo of the display taken with a photo camera? It looks like your display has phasing problem.
 
Already tried to change the wallpaper? :D And without this app ( i don't know what is) are there anyway these bars?

I don't understand why you say that is the monitor and not the application :confused:
 
qap said:
Already tried to change the wallpaper? :D And without this app ( i don't know what is) are there anyway these bars?

I don't understand why you say that is the monitor and not the application :confused:
Click to expand...
I've been quite bad at explaining this so I'll try again :eek:

When I run the application and view those download bars, they spread out over the app. (Under Windows 7)

I took a screenshot to see if it was a display issue so I could view it on my other machines.

On other displays the screenshot does not have those glitch lines. But no matter what OS I'm in if I look at the screenshot I see glitch lines (like in the photo I took).

+If I zoom into the screenshot the glitch lines fade.
+If I move the screenshot off the size of the display (so the real lines are no longer in view) the glitch lines fade.


It's not the application (Steam). That's the only thing I can be sure of.

Update: I created a similar pattern in Photoshop Elements in OSX - http://satansam.co.uk/ftp/IMG_6846.JPG. The black+white is the image, the grey is supposed to be a block colour with no patterns.
 
Last edited:
Ok, I'm pretty sure I misread this twice but in order to verify what you explained you would need a software screen capture and not a photograph of your monitor. In Mac OS is Shift + Cmd + 3 and in Windows is Print Screen or use the Snipping tool.
 
Sorry about that. For some reason I managed to open the photo twice.

Those look like some sort of ghosting effect induced by the high contrast pattern in the download progress bar in steam. The more of those line you have on the screen, the more pronounced the ghosting effect is. Try moving the steam windows sideways, away from the screen and the ghosts fade away.

It does indeed happen to my 27", which is a bit worrying. It only seem to appear at maximum screen resolution. I wonder if the refresh rate can be changed on these screens.
 
Interesting. It does the exact same thing on my mid 2010 27' iMac.

Made a test image :
attachment.php


Never noticed this before. I'd like to know how many external display have this issue. (not necessarily the iMac)
 

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I have an Apple 27" Cinema Display (external not in iMac) and 2 23" ACDs on my Mac Pro and nothing either in OSX or Win 7.

Tried on my mate's 2009 27" iMac and there's no problem there either.

If you're getting the problem exactly the same on both the screenshot and the image your eyes are seeing (photo) then that would seem to indicate an error with the signal from the OS or GPU rather than the display. The screenshot will not have anything to do with the display and just shows that the display is functioning properly and displaying the 'faulty' signal from OS/GPU??
 
ndraves said:
I have an Apple 27" Cinema Display (external not in iMac) and 2 23" ACDs on my Mac Pro and nothing either in OSX or Win 7.

Tried on my mate's 2009 27" iMac and there's no problem there either.

If you're getting the problem exactly the same on both the screenshot and the image your eyes are seeing (photo) then that would seem to indicate an error with the signal from the OS or GPU rather than the display. The screenshot will not have anything to do with the display and just shows that the display is functioning properly and displaying the 'faulty' signal from OS/GPU??
Click to expand...

No, when you make a software screenshot (like with Preview), the lines are not in the image. (when you zoom you see that there is no variation in the background color).
 
/V\acpower said:
No, when you make a software screenshot (like with Preview), the lines are not in the image. (when you zoom you see that there is no variation in the background color).
Click to expand...

Just had a look at the screenshot image above (...Capture.png) rather than the photo and I get the vertical lines moving across the Win 7 desktop blue outside of the Steam window.

I then dragged the browser window across to my 23" and the vertical bars disappeared. No refresh, just no there on the 23" ACD but they are there on the 27" ACD. When having the image split across the 2 displays the bars are there on the 27" and then disappear on the 23".

I jumped to my conclusion above a little quickly but am now really intrigued????

Presumably this has this do with the way the 27" ACD processes the signal coming from the GPU for that combination of blue and the high contrast bars in the Steam window???
 
ndraves said:
Presumably this has this do with the way the 27" ACD processes the signal coming from the GPU for that combination of blue and the high contrast bars in the Steam window???
Click to expand...

Can you change the refresh rate of the ACD? The iMac doesn't allow for this.
 
Interesting.

I have tried to create different pattern of black and white, they all don't make the "ghost lines".

1st line : 1 space white, 2 spaces black, 1 space white, etc...

2nd line : 1 space white, 1 space black, 1 space white, etc... (like my first one)

3rd line : irregular pattern.
 

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Well I'm hoping that this can be fixed with a firmware update!
 
maxinc said:
Can you change the refresh rate of the ACD? The iMac doesn't allow for this.
Click to expand...

No, neither the 27" or either the 23" ACD have adjustable screen refresh rates. I also have a Dell plugged into my Mac and that has the option to select the refresh rate.
 
/V\acpower said:
Interesting.

I have tried to create different pattern of black and white, they all don't make the "ghost lines".

1st line : 1 space white, 2 spaces black, 1 space white, etc...

2nd line : 1 space white, 1 space black, 1 space white, etc... (like my first one)

3rd line : irregular pattern.
Click to expand...

None of these give any problems with my displays. I did notice however that the aliasing pattern happening with the .png image supplied above not only gives the lines across the remainder to the image in the browser window but also across my OSX desktop background all the way to the edge of the screen (more apparent in negative contrast mode, Ctrl+Option+Cmd+8).


Dagless said:
Well I'm hoping that this can be fixed with a firmware update!
Click to expand...

Not sure this is an easy firmware fix. Looks to be integral into the way the 27" display processes that exact signal from the GPU.

Do you get the problem anywhere else but with this combo of Steam + Win 7 desktop?
 
maxinc said:
The magic number is 2px by 2px.

Image
Click to expand...

Something further that is a bit weird. I had a look at the image in this post and I didn't get any problems. Dragged my windows around for something else and noticed that I had the aliasing.

So when I move the page by the window it sometimes is there and sometimes is not. But if it's there and I scroll the page (not moving the window) then the aliasing remains as it slides up and down the page, there if it was before scrolling or not there if not there before scrolling.

As though when moving the window and dropping it the image is re-rendered and something appears and sometimes doesn't. But when scrolling when the image is just translating pixels and not being re-rendered by the OS remains as before. Either there or not.

Might it have something to do with slightly ill matched 60Hz clocks in the GPU/OS and the signal processing on the panel? Hence why it appears some of the time (signal mismatched) and not others (signal sent between mismatching cycles)???
 
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